Guest Blackwater Posted July 19, 2007 Posted July 19, 2007 On Wed, 18 Jul 2007 22:26:21 GMT, simberg.interglobal@org.trash (Rand Simberg) wrote: >On Wed, 18 Jul 2007 21:20:37 GMT, in a place far, far away, >bw@barrk.net (Blackwater) made the phosphor on my monitor glow in such >a way as to indicate that: > >>>>>>>I doubt it. In many ways a reusable is far more complex than an expendable. >>>>>>>You justify this complexity, and cost, by flying it more than once. >>>>>> >>>>>> But the complexity works AGAINST you trying to re-use the >>>>>> component. Every component interacts with many others, it >>>>>> quickly gets out of hand. Why do you think there are so >>>>>> often last-second delays launching shuttles ? ALL those >>>>>> little parts have to be tweaked, for a few minutes, into >>>>>> harmonious operation. They can BARELY do it. Actually, they >>>>>> CAN'T do it ... they just fudge on the safety parameters >>>>>> and launch anyway. >>>>> >>>>>It is a logical fallacy to draw general conclusions from a single data >>>>>point, even if it's the only one you have. The Shuttle doesn't tell >>>>>us much useful about reusable vehicles. Particularly since much of it >>>>>isn't even reusable. >>>> >>>> Show me how to build a reusuable vehicle that ISN'T >>>> burdened-down by it's own complexity and requirements >>>> for reusability and I'll consider modifying my assessment. >>> >>>There is nothing wrong with complexity. A modern airliner is quite >>>complex. The primary difference between an air transport and a space >>>transport is the much higher fllight rate of the former. >> >> Um ... it's a little more involved than that. >> >> Think about it for a while. > >Believe me, I've thought about it a great deal. As an aerospace >professional, I've even been paid to think about it, and published >papers on it. Have you? Clearly I should be ... Paid to write sci-fi plots eh ? Multiusable do-everything launch & mission vehicles are guarenteed to be too complex, too bulky and too expensive. They are NOT "jetliners with rockets" by ANY stretch of the imagination. Given the current technology (and political system) if you want economy and reliablity you go with standardized, modular, one-time-use components, heavy on the SRBs. NASA seems to agree and has put its money down for just that. Quote
Guest Blackwater Posted July 19, 2007 Posted July 19, 2007 On Wed, 18 Jul 2007 14:43:19 -0400, "Jeff Findley" <jeff.findley@ugs.nojunk.com> wrote: > >"Blackwater" <bw@barrk.net> wrote in message >news:469e35f5.7727078@news.east.earthlink.net... >> On Wed, 18 Jul 2007 10:01:34 -0400, "Jeff Findley" >> <jeff.findley@ugs.nojunk.com> wrote: >> >>> >>>"Blackwater" <bw@barrk.net> wrote in message >>>news:469e0eb6.6752038@news.east.earthlink.net... >>>> On Wed, 18 Jul 2007 08:33:47 -0400, "Jeff Findley" >>>> <jeff.findley@ugs.nojunk.com> wrote: >>>> >>>>> >>>>>"Blackwater" <bw@barrk.net> wrote in message >>>>>news:469d19a5.31631187@news.east.earthlink.net... >>>>>> Geez ... we REALLY need 'warp drive' or something. >>>>>> Reaction rockets are just TOO ... expensive, bulky, >>>>>> inefficient and dangerous. >>>>> >>>>>Not really. >>>> >>>> Really ? >>>> >>>> Go build a big rocket and see what it does >>>> to your bank balance. >>>> >>>>>What we really need is to stop throwing away the rockets after >>>>>every flight. >>>> >>>> Sounds great - but it never seems to work out in practice. >>>> The stresses of operation and plunging back again combined >>>> with the need for lightweight components ... well ... I >>>> wouldn't want to ride a re-used booster. >>>> >>>>> Maybe start with a fully reusable first stage then work up to >>>>>a fully reusable upper stage, giving a fully reusable TSTO. >>>> >>>> Bert Rutan may have come up with a viable fix - use some >>>> kind of aircraft as the "1st stage". Nowdays it can be fully >>>> robotic, autopiloted. A big wing with engines optimized for >>>> high altitudes and you can cut the first 60,000 feet off >>>> your trip. >>>> >>>> Use a simple SRB as the '2nd stage'. Save the expensive stuff >>>> for the final orbital-insertion stage. >>>> >>>> It would be a help ... but it wouldn't add-up to anywhere >>>> near the necessary order-of-magnitude price reduction needed >>>> to properly commercialize space. Scramjet-powered orbital >>>> air/spacecraft - someday, maybe ... >>>> >>>>>> Got to knock at least >>>>>> an order of magnitude off the price to orbit. If >>>>>> you know any physics geniuses, buy 'em a few beers >>>>>> and then give 'em a mission before they're sober >>>>>> enough to change their minds. >>>>> >>>>>It ought to be possible to knock more than an order of magnitude off by >>>>>focusing on making launch vehicles reusable and more efficient to turn >>>>>around between flights. >>>> >>>> I don't believe it. >>> >>>Why not? Airliners aren't expendable. >> >> NOT the same animal, NOT the same jungle. Spacecraft have >> to be built much lighter, more fragile, and then are >> sujected to extreme accelerations, vibrations, thermal >> distortions and corrosive chemicals. > >So what. Just because they're not exactly the same animal doesn't mean that >there isn't room for improvement with rockets. Throwing away your engines >on each and every flight is more than a bit silly if your long term goal is >to reduce reoccuring launch costs. SURE there's room for improvement. But how MUCH improvement ? As for the economy of reusable engines, I dunno about that. Something built to give it's all for a one-time event, and be nothing but a burnt-out shell afterwards, may indeed be cheaper than something built robustly enough to be used dozens of times. Not to mention that by the time you get to use #23 ... well ... kind of like driving cross-country in a '72 Pontiac with 129,000 miles on the odometer - except if your rocket engine fails you DIE rather than just being stuck in Utah. As with much machinery, 'robust' means "heavy". A reusable rocket engine has to resist a series of pressure, temperature and vibration extremes. That means the parts have to be built extra strong - and thus extra heavy. Weight is a VERY important consideration in space flight. Every ounce in the booster is another precious ounce of cargo you can't take with you. To enhance reusability, "complexity" may also be involved. Fancier cooling schemes, more redundancy. Every time you add an element that might interact with another element you add "complexity" and greatly increase the chances of an unexpected interaction. Beyond a point, you gain very little by adding more "complexity" - and then start to go downhill in terms of reliability. Now, instead, consider the single-use booster. SRBs are old hat and - if you design any joints properly - about as simple and reliable as you can get. Nothing to them. For a single-use liquid- fueled engine it should be possible to make use of some of the newer carbon-fiber or carbon nanotube composites to give the combustion chamber mechanical strength. Weight is decreased. You only need a thin inner layer of metal into which you stamp your channels for fuel and oxidizer. That inner lining, AND the composites, will be "cooked" by the time the burn is finished. Can't use them again - but then they didn't COST much and didn't WEIGH much. Does the lower cost and weight stand up against the hypothetical 24 reuses of the 'robust'/complex engine ? Maybe ... especially if you understand that the 'robust' engine may NOT quite live up to it's projected lifespan before going boom . Also, those 'robust' engines are a considerable "investment" - time and money. If you find they're not quite what you wanted, you're still kind of STUCK with them for awhile. The cheaper, simpler engines are not such a great investment, you can specify changes when you order the next half-dozen. >>>It's part of the reason we can >>>justify the extreme costs to develop, build, and fly super efficient high >>>bypass turbofan engines for them. The other big reason is the huge demand >>>for passenger air travel. >> >> Actually, the passengers fly for "free" - it's the CARGO >> under their feet that generates the profits. > >Then lets add the huge demand for fast cargo transport as a reason the jet >engine companies keep eeking out more performance for less fuel out of next >generation engines. Hell yes ! It's dollars per pound/mile ... whether the pounds represent people or FedEx packages. A one-percent improvement in fuel economy translates into many millions of dollars per year. An extra ten knots of speed means FedEx gains x-many minutes per month in which to deliver packages - so it can thus handle MORE of them. >>>> It would require a DRASTIC simplification of the design, so >>>> fewer things could go wrong and fixes would be quick cheap >>>> and easy. Nobody seems able to do that, not America, not >>>> Russia, not China, not Japan, not France. If anything, >>>> designs have just become MORE complex and fragile. >>> >>>I doubt it. In many ways a reusable is far more complex than an >>>expendable. >>>You justify this complexity, and cost, by flying it more than once. >> >> But the complexity works AGAINST you trying to re-use the >> component. Every component interacts with many others, it >> quickly gets out of hand. Why do you think there are so >> often last-second delays launching shuttles ? ALL those >> little parts have to be tweaked, for a few minutes, into >> harmonious operation. They can BARELY do it. Actually, they >> CAN'T do it ... they just fudge on the safety parameters >> and launch anyway. > >Why use the shuttle as an example. As I said before, it's clear to everyone >who's looked at the shuttle that serious design compromises were made during >development which decreased development costs but greatly increased >reoccuring costs. Design the next reusable vehicles for true reusability >and do it with current technology. Technology has come a long way since the >early 70's. But the political/economic factors which caused all the 'compromises' in the shuttles design STILL exist. The next shuttle will STILL be designed by committee, and that result passed through other committees and finally through committees of self-interested politicians who will want all kinds of changes in design and manufacture as so to direct as much money as possible into their state and their contributors pockets. "Shuttle-II" will be just as much of a mess as the existing STS. Note too that they REALLY tried to build the shuttles SRBs so they could be re-used. Alas, between the heat and vibration and smacking into the ocean ... the things were trash after the first use. IMHO, forget re-usable boosters. Just build the cheapest, lightest, simplest single-use units possible. >>>> As for "efficiency" ... rocket efficiency isn't going to >>>> increase much. It's the physics. Recovery/repair/reuse >>>> efficiency COULD improve considerably, but then we still >>>> need robust and simplistic designs to make that possible. >>> >>>Time for a reality check. >> >> Been there, checked-in. Waiting for you to show up :-) >> >> USA porkbarrel politics work against efficiency and >> simplicity - but this isn't the case in the other >> spacefaring countries. If France or Russia COULD do >> it all that more cheaply and better they WOULD have. >> The observable reality says "This is as good as it gets". > >Neither is willing to spend the big bucks necessary for development of >reusable launch vehicles big enough to replace their existing launchers when >they're still making money on their expendables. Actually, Russia barely >has money to keep flying their existing expendables, nevermind developing > anything new. I don't think porkbarrel politics has much to do with it. France is much more "socialist" than the USA. If cost-savings through reusability could be persuasively argued the govt would get the industy to switch - and not take too much profit from the excercise. Russia, for now, is indeed too poor to switch horses. Their existing system works very well so there's little motivation for a big investment in newer or reusable technology. However in the 1970s, the USSR still did have some spare cash and an iron grip on industry. If reusable had sounded good then, they could have gone that way a LOT quicker than 'democratic' nations. They didn't. China, for now, is essentially copying Russian technology. However it DOES have great wads of cash and sees a spacefaring future for itself. Expect them to do something spectacular a lot sooner than we, or their propaganda bureau, predicts. Either a moon landing or a BIG space-station (they've been very interested in benifits of inflatable structures). With that kind of future in mind, you'd expect them to be keen on reusable boosters and such. So far however, they do not seem all that interested. >>>The cost of fuel and oxidizer for a launch vehicle is absolutely tiny >>>compared to overall launch costs. I personally like LOX/kerosene since >>>both >>>are widely available and the kerosene is pretty dense. >> >> Agreed and agreed ... it's not the fuel (even though LOX requires >> a lot of energy to make and a lot of care to handle). It's the >> MACHINE the fuel goes into. > >A machine that's typically thrown away after each and every flight. Boosters INTENDED for a single use are relatively simple and inexpensive. It's the damned shuttle ... we got all the bulk, complexity and expense associated with reusability, but only the actual shuttles get reused. Even then, the engines and several other systems need a major overhaul after each flight. >> It's the highly-trained PEOPLE required >> to make sure everything's right. > >Parly required because every flight of an expendable is of an unflown >vehicle. The full up test flight is the flight the customer paid for. > >> It's the huge FACILITIES and >> INFRASTRUCTURE required to support everything. > >Sure, and a lot of that is to build the vehicles in the first place, then >you throw the vehicle away and build yet another vehicle. > >> If these were >> private ventures you'd also have to add INSURANCE to the mix. > >Of course, but the hope is that reusables will have intact abort modes, so a >launch failure would mean you have to recover the payload and try again. >With many expandable launch failures, you not only have to build a new >launch vehicle to try again, but you also have to build a new payload as >well. Which type of failure costs the insurance company more money, which >is passed on to its customers as higher insurance premiums? An boost-phase abort mode ??? That would mean soft-landing a big tank, possibly with a fire at one end, of liquid oxygen and something extremely flammable in a desert. I sure as hell wouldn't go NEAR the thing ... :-) IMHO, you'd have to sacrifice the boosters and plan to recover only the payload. As the payloads often cost more than the rest of the vehicle combined, this makes good sense. I'm suprised the new Ariane isn't set up to pop away the cargo capsule on a milliseconds notice. >> Rockets are still essentially custom-made one-off machines. >> There's no assembly line, no grand template, no army of >> industrial robots, no real "standard components". This makes >> them incredibly expensive. Dealing with every issue the >> engineers know about or can imagine makes them insanely >> complex and expensive. This can't change unless designs >> are somehow simplified and sufficient VOLUMES of a 'standard >> rocket' are ordered so that assembly-line economics CAN >> begin to have an effect. > >Large aircraft assembly processes are fairly similar to launch vehicle >assembly processes. They're very expensive to make, so we simply don't >throw them away after every flight. In fact, many aircraft fly for decades, >being demoted to cargo only flights or to be sold off to foreign countries >who continue to fly them for many more decades. You just don't throw away >such an expensive asset when you're done with it. As I said to someone ... rockets ain't airplanes, either in design or in their economics. However - by simplifying design, using standardized components and 'modular' systems, you COULD gain some of the advantages of assembly-line economics. NASAs next toys are kind-of like that, though I doubt they took "simplify" to heart (doesn't profit as many contractors & politicians). >>>The Saturn V first >>>stage burned something like 200,000 gallons of "rocket grade" kerosene >>>(RP-1). If you're paying $5 per gallon for your kerosene, that's only $1 >>>million dollars per launch. That's a pitiful fraction of the overall >>>costs >>>for an expendable Saturn V launch. And LOX is extremely cheap, litterally >>>pennies per pound, in industrial quantities since air is the raw material >>>you start with. One astronautix.com page says NASA was paying $0.08 per >>>kg >>>in the 1980's for LOX. >>> >>>Clearly, it's not physics that dictates the cost since the fuel and >>>oxidizer >>>needed are relatively cheap. >> >> The physics I was speaking of relate to how much bang you >> can get out of a rocket engine of a given size. It's a >> function of ignition-chamber pressure, subsequent gas >> expansion and velocity plus the weight of the components. >> X-energy IN, Y-energy translated into thrust. >> >> Hasn'tchanged much since the 60s. It defines the vehicle/cargo >> weight ratio. > >You're missing the point. With the cost of fuel so low, why is the >vehicle/cargo weight ratio important ? Why not optimize the design for the >lowest cost per lb of cargo to LEO? It's a different optimization >constraint which will drive you towards a completely different design than >the "performance uber alles" philosophy of the LOX/LH2 crowd. Fuel is more than weight, it's BULK. Low-effeciency engines mean your booster has to carry more fuel and be physically LARGER to accomodate it. Large uses more materials. Large introduces more vibrational modes. Larger means more surface area for your cyro tanks - and therefore thermal expansion/ contraction and thus more insulation and therefore more weight and so on and so forth. You really want your rocket to be as small as possible. Thus, you want high efficiency engines. Materials and heat dissipation limit your chamber pressures. You can go for bigger chambers but now you've got to use bigger fuel pumps. >> [snips] >> >> I prefer a completely DISPOSABLE vehicle. Build it to >> make exactly ONE flight - build it simple. Designing >> for re-use adds mass and complexity. It also locks you >> into the one design. You've made your 'investment' and >> now you're stuck. > >Tell that to the guys flying B-52's. They're definately not quite the same >vehicles as when they were built. One of these days, the funding for >upgrading the engines to turbofans will come through and they'll even look >different on the outside. ;-) Yea, the '52 has certainly evolved - but then aircraft ARE easier to modify. It's also easier to test each modification, you'll only kill a few soldiers if it doesn't work ... >For that matter, look at the shuttle. There have been numerous upgrades >over the years along with even more numerous proposed upgrades that were >never funded. You certainly can refit existing airframes with newer >technologies and keep flying them. You can refit - but WITHIN LIMITS. They're not going to alter the shuttles external profile or major structural components. There's only so much room for certain kinds of components. The overall weight and balance can't change much. They're not going to completely re-wire it. Anyhow, I don't have much against reusable mission vehicles. Not much anyway. I'm more concerned with the boosters. Even thus, for many kinds of missions, a more conventional "capsule" would serve ... and you can throw it away later. You can make several kinds of capsules, each optimized for a specific kind of job. I think this would actually be cheaper and better than trying to build a does-it-all machine. >> The easiest 'disposable' route for spacecraft is to make >> maximum use of SRBs. Alone, or combined with LFRs so a >> range of thrust adjustment is possible, they're really >> a good way to add oomph without adding much cost. Not >> much more than a tube packed with 'powder'. > >Only if you like paying for entirely new vehicles after each and every >flight and will accept the cost and safety issues which arise from flying >expendables. The safety issues are managable. The single one the shuttle program has failed to deal with is an incident where you may have to detach the SRBs early on, while they're still burning full power. This isn't too difficult to cope with, it's just that the current framework isn't designed to do the job. As for cost, SRBs do NOT have to be extremely expensive. You KNOW we're getting ripped-off by Thiokol - but they've managed to secure a position as sole shuttle SRB manufacturer ( I wonder how they managed that ?). New launch systems open the door to new bidders ... and, in theory, prices could be negotiated down considerably. Oh, and remember what I said about the evils of "bigness" ? That applies to SRBs too. The shuttles SRBs are difficult to make because they're so large. The propellant is cast in large 'pills' that really want to crack as they cure. The tube assembly had to be multi-jointed ... and we know what THAT caused. More, slimmer, SRBs may be the ticket. But, if you can come up with a really bare-bones liquid booster that doesn't leak fuel all over the place, doesn't cost a bleedin' fortune and can REALLY be reused five+ times then by all means sell it to NASA. Of course there's always the Rutan solution - nitrous oxide and ground-up tire rubber :-) >Intact abort is a good thing. It helps solve a lot of nagging problems with >expendables independent of the whole launch cost thing. As I said, TOTALLY intact abort is almost certainly a pipe dream. Damn the boosters - SAVE THE PAYLOAD ! Satellites (and people) are EXPENSIVE. Quote
Guest Dave O'Neill Posted July 19, 2007 Posted July 19, 2007 "Blackwater" <bw@barrk.net> wrote in message news:469cb0b4.4766375@news.east.earthlink.net... > Odd Factoid revealed on BBC ... > > It's actually ILLEGAL for Brits to fly into space. > > http://www.bbc.co.uk/mediaselector/check/player/nol/newsid_6900000/newsid_6902400?redirect=6902415.stm&news=1&nbwm=1&bbram=1&nbram=1&bbwm=1 > > Apparently the government implemented the policy long ago, > assuming it would prevent aerospace resources from being > "wasted" on human flight. The clip is inaccurate in what it says. The government banned British citizens from becomming ESA astronaunts where the government would be paying. There have been several British citizens flying in space. Helen Sharman was the first. Two of NASA's astronauts have dual nationality (it's really hard to give up a British passport). Dave Quote
Guest Alan Anderson Posted July 20, 2007 Posted July 20, 2007 bw@barrk.net (Blackwater) wrote: > As with much machinery, 'robust' means "heavy". A reusable > rocket engine has to resist a series of pressure, temperature > and vibration extremes. That means the parts have to be built > extra strong - and thus extra heavy. Weight is a VERY important > consideration in space flight. Every ounce in the booster is > another precious ounce of cargo you can't take with you. If you're worrying about ounces of cargo, you're focusing on the wrong thing. Heavy is fine; it just takes fuel to compensate for it, and fuel is cheap . Weight should NOT be as important as you are making it. What's important is COST (oh, and reliability). Quote
Guest Jeff Findley Posted July 20, 2007 Posted July 20, 2007 "Blackwater" <bw@barrk.net> wrote in message news:469fd78d.232031@news.east.earthlink.net... > On Wed, 18 Jul 2007 14:43:19 -0400, "Jeff Findley" > <jeff.findley@ugs.nojunk.com> wrote: >>So what. Just because they're not exactly the same animal doesn't mean >>that >>there isn't room for improvement with rockets. Throwing away your engines >>on each and every flight is more than a bit silly if your long term goal >>is >>to reduce reoccuring launch costs. > > SURE there's room for improvement. But how MUCH improvement ? > > As for the economy of reusable engines, I dunno about that. > Something built to give it's all for a one-time event, and > be nothing but a burnt-out shell afterwards, may indeed be > cheaper than something built robustly enough to be used > dozens of times. Not to mention that by the time you get > to use #23 ... well ... kind of like driving cross-country > in a '72 Pontiac with 129,000 miles on the odometer - except > if your rocket engine fails you DIE rather than just being > stuck in Utah. All (sane) liquid fuel rocket engines are reusable. Why? Because you want safety margins. You typically design liquid fueled rocket engines for multiple firings (it's often nice to test fire them before you use them) and design them to last for firings far longer than what's needed for a single mission. Take a look at the DC-X/XA program where RL-10 engines were routinely used over and over without pulling them from the vehicle. > As with much machinery, 'robust' means "heavy". A reusable > rocket engine has to resist a series of pressure, temperature > and vibration extremes. That means the parts have to be built > extra strong - and thus extra heavy. Weight is a VERY important > consideration in space flight. Every ounce in the booster is > another precious ounce of cargo you can't take with you. Rocket engines are already fairly robust, otherwise they'd tend to go "boom" a lot more often than they do. Even the highly strung SSME has gotten to the point where you don't have to tear it down after every flight to inspect it and rebuild it. > To enhance reusability, "complexity" may also be involved. > Fancier cooling schemes, more redundancy. Every time you > add an element that might interact with another element > you add "complexity" and greatly increase the chances of > an unexpected interaction. Beyond a point, you gain very > little by adding more "complexity" - and then start to go > downhill in terms of reliability. Doubtful, as existing liquid fueled rocket engines are already reusable. This is why throwing them away after every flight is so silly! >>Why use the shuttle as an example. As I said before, it's clear to >>everyone >>who's looked at the shuttle that serious design compromises were made >>during >>development which decreased development costs but greatly increased >>reoccuring costs. Design the next reusable vehicles for true reusability >>and do it with current technology. Technology has come a long way since >>the >>early 70's. > > But the political/economic factors which caused all > the 'compromises' in the shuttles design STILL exist. > The next shuttle will STILL be designed by committee, > and that result passed through other committees and > finally through committees of self-interested politicians > who will want all kinds of changes in design and manufacture > as so to direct as much money as possible into their state > and their contributors pockets. "Shuttle-II" will be just > as much of a mess as the existing STS. This is why we likely won't see reusable rocket stages emerging from "the usual suspects". It's far more likely that they'll emerge from the start-ups, who are currently focusing on suborbital tourism. The new market of tourism is likely to change the plitical/economic status quo, since "the usual suspects" are not involved. The market forces for tourism naturally demand high flight rates, which drives you towards reusability. "The usual suspects" simply aren't that interested in high flight rates. They tend to lean towards more payload on fewer flights, which results in low flight rates. With such low flight rates, you simply cannot justify reusable launch vehicles on economic grounds. > Note too that they REALLY tried to build the shuttles SRBs > so they could be re-used. Alas, between the heat and vibration > and smacking into the ocean ... the things were trash after > the first use. IMHO, forget re-usable boosters. Just build > the cheapest, lightest, simplest single-use units possible. They do clean them out and reuse them. It's just that solids are really bad when it comes to reuse. It's a lot harder to refurbish them than it was to fill up the DC-X/XA's tanks with more fuel and oxidizer and simply fly it again. > Boosters INTENDED for a single use are relatively simple > and inexpensive. It's the damned shuttle ... we got all > the bulk, complexity and expense associated with reusability, > but only the actual shuttles get reused. Even then, the > engines and several other systems need a major overhaul > after each flight. Sorry, but much of the shuttle isn't reusable. Much of it is refurbished and rebuilt after every flight. It's not a good example of a reusable vehicle. The DC-X/XA is a far better example. >>Of course, but the hope is that reusables will have intact abort modes, so >>a >>launch failure would mean you have to recover the payload and try again. >>With many expandable launch failures, you not only have to build a new >>launch vehicle to try again, but you also have to build a new payload as >>well. Which type of failure costs the insurance company more money, which >>is passed on to its customers as higher insurance premiums? > > An boost-phase abort mode ??? That would mean soft-landing > a big tank, possibly with a fire at one end, of liquid > oxygen and something extremely flammable in a desert. > I sure as hell wouldn't go NEAR the thing ... :-) Fire is possible, but more likey is a problem in the engine that would require you to simply shut it down. You can shut down liquid engines quite simply by shutting off valves to the engine. You design the thing with multiple engines. You design each stage to use 5 engines at 80% maximum thrust. If you lose one engine, you throttle up the others to 100% and continue the mission since you've not lost any performance with one engine out. Some expendables have had this built in. For example, the Saturn V's first and second stages could tolerate engine outs at some points of the flight and still complete the mission. If you lose two out of five engines, then you've got an abort on your hands only if it comes at a bad time. This is because you typically throttle your engines back towards the end of the burn to keep g-loads down. At any rate, say you lose two engines early on and simply don't have enough thrust to complete the mission. You'd want to keep your remaining engines at 100% to burn off all the fuel in the tanks, and then you land your reusable stage in much the same way you would if it were a nominal mission. Making a vehicle reusable means you already have recovery systems built into the stage. You use them during an abort to recover the stage, and the payload if it's an upper stage. Note that the shuttle can, theoretically, do some of this, which is why there are abort modes built into the system. Depending on the emergency, it can abort to the launch site, to a trans-Atlantic site, or to orbit (possibly too low to complete the mission, but high enough to give you plenty of time to let you pick the safest landing site). > IMHO, you'd have to sacrifice the boosters and plan to > recover only the payload. As the payloads often cost > more than the rest of the vehicle combined, this makes > good sense. I'm suprised the new Ariane isn't set up > to pop away the cargo capsule on a milliseconds notice. Why? I'm assuming a reusable that can return a payload from LEO that's just as big as the one it can launch, so there is no fundamental reason you can't burn off any remaining fuel and make an emergency landing with the payload intact. >>Large aircraft assembly processes are fairly similar to launch vehicle >>assembly processes. They're very expensive to make, so we simply don't >>throw them away after every flight. In fact, many aircraft fly for >>decades, >>being demoted to cargo only flights or to be sold off to foreign countries >>who continue to fly them for many more decades. You just don't throw away >>such an expensive asset when you're done with it. > > As I said to someone ... rockets ain't airplanes, either > in design or in their economics. Funny how the DC-X/XA was operated much less like traditional rockets and much more like a jet aircraft. After a flight they could quickly turn it around and fly it again. There's nothing fundamenal which prevents you from operating in this way. In fact, this was one of the big criticisms of rocket engines before DC-X/XA, so quick turn around was one of its design goals. This design goal was met and demonstrated during an actual test flight prgram. >>You're missing the point. With the cost of fuel so low, why is the >>vehicle/cargo weight ratio important ? Why not optimize the design for >>the >>lowest cost per lb of cargo to LEO? It's a different optimization >>constraint which will drive you towards a completely different design than >>the "performance uber alles" philosophy of the LOX/LH2 crowd. > > Fuel is more than weight, it's BULK. Low-effeciency engines > mean your booster has to carry more fuel and be physically > LARGER to accomodate it. Tanks are cheap. Making them bigger, in the design stage, doesn't add much to the overall costs of the vehicle when you go to build it. > Large uses more materials. Materials are cheap compared to the overall program, especially when you plan to use them for more than one flight. Look at the cost of the ET's for the shuttle program. They're expendable because they're relatively cheap to make. > Large > introduces more vibrational modes. Which is why you have aerospace engineers designing the thing. > Larger means more surface > area for your cyro tanks - and therefore thermal expansion/ > contraction and thus more insulation and therefore more > weight and so on and so forth. Actually, bigger tanks means less tank surface area to tank volume, which means it's actually easier to deal with these sorts of issues. It seems as though you're not understanding the scaling laws inherent in aerospace design. > You really want your rocket to be as small as possible. Not necessarily. Some things get easier as you make the vehicle bigger, like tank insulation and tps. A reentry vehicle that's mostly empty tankage makes for easier tps since it will tend to decellerate more in the thin upper atmosphere than a vehicle that's all dense payload and heavy engines, like the shuttle. > Thus, > you want high efficiency engines. You want that anyway. You can buy very efficient LOX/kerosene engines today. Look at the Russian engines on Atlas V. Very good ISP (for kerosene) with nice, dense kerosene fuel, making for much smaller tanks than LH2 engines. > Materials and heat dissipation > limit your chamber pressures. You can go for bigger chambers > but now you've got to use bigger fuel pumps. Or you go for several engines. Look at the RD-170. It's one set of turbopumps with four chambers. It puts out about 1,700,000 lbs of thrust at sea level, which is a tad more than the venerable F-1 engine. However, the RD-170 has a sea level ISP of 309 seconds while the F-1's sea level ISP is only 265 seconds. With a cluster of five RD-170 engines, you've got 8,500,000 lbs of thrust to play with. I think that would be plenty big while giving you the ability to design for single engine out capability. ;-) >>Tell that to the guys flying B-52's. They're definately not quite the >>same >>vehicles as when they were built. One of these days, the funding for >>upgrading the engines to turbofans will come through and they'll even >> look >>different on the outside. ;-) > > Yea, the '52 has certainly evolved - but then aircraft ARE > easier to modify. It's also easier to test each modification, > you'll only kill a few soldiers if it doesn't work ... It's easier to test modifications becuase it's reusable and you, hopefully, get the test vehicle back after the flight! Intact recovery of a reusable means you can inspect the thing after it flies and see how your modifications performed. The flight may be successful, but you can inspect it and easily find out how close to failure it actually came. This is much harder to do with an expendable whose stages are typically destroyed during flight and end up in pieces at the bottom of the ocean (lower stages) or end up burning up completely in the atmosphere (upper stages) when they reenter after doing their job. >>For that matter, look at the shuttle. There have been numerous upgrades >>over the years along with even more numerous proposed upgrades that were >>never funded. You certainly can refit existing airframes with newer >>technologies and keep flying them. > > You can refit - but WITHIN LIMITS. They're not going to alter > the shuttles external profile or major structural components. > There's only so much room for certain kinds of components. The > overall weight and balance can't change much. They're not going > to completely re-wire it. > > Anyhow, I don't have much against reusable mission vehicles. > Not much anyway. I'm more concerned with the boosters. Even > thus, for many kinds of missions, a more conventional "capsule" > would serve ... and you can throw it away later. You can make > several kinds of capsules, each optimized for a specific kind > of job. I think this would actually be cheaper and better than > trying to build a does-it-all machine. Not necessarily. Using expendable launch vehicles means you're constrained on how big you can make your capsules. This typically leads to capsule designs that are very dense, making for hotter reentries and much more challenging tps designs. > >>> The easiest 'disposable' route for spacecraft is to make >>> maximum use of SRBs. Alone, or combined with LFRs so a >>> range of thrust adjustment is possible, they're really >>> a good way to add oomph without adding much cost. Not >>> much more than a tube packed with 'powder'. >> >>Only if you like paying for entirely new vehicles after each and every >>flight and will accept the cost and safety issues which arise from flying >>expendables. > > The safety issues are managable. Shure, if you like to pay the cost of certifying and inspecting each and every part before each and every flight. Sanely designed reusables are made up of components that last far longer than one flight, so your inspection requirements are far less per flight. This directly leads to lower per flight launch costs. > The single one the shuttle > program has failed to deal with is an incident where you > may have to detach the SRBs early on, while they're still > burning full power. This isn't too difficult to cope with, > it's just that the current framework isn't designed to > do the job. Actually it is difficult to deal with. The STS design originally incorporated thrust termination for the SRB's, but it was dropped when it became clear that the thrust transients involved in thrust termination would tear the orbiter apart. This is one reason I dislike large solids. it's very hard to turn them off in a non-violent way. > As for cost, SRBs do NOT have to be extremely expensive. > You KNOW we're getting ripped-off by Thiokol - but they've > managed to secure a position as sole shuttle SRB manufacturer > ( I wonder how they managed that ?). New launch systems open > the door to new bidders ... and, in theory, prices could be > negotiated down considerably. They managed that because the flight rate is so low you can't justify having more than one supplier for things like SRB's, ET's, or engines. Low flight rate is a huge problem to launch vehicle economics. > Oh, and remember what I said about the evils of "bigness" ? > That applies to SRBs too. The shuttles SRBs are difficult > to make because they're so large. The propellant is cast > in large 'pills' that really want to crack as they cure. > The tube assembly had to be multi-jointed ... and we know > what THAT caused. More, slimmer, SRBs may be the ticket. > > But, if you can come up with a really bare-bones liquid > booster that doesn't leak fuel all over the place, doesn't > cost a bleedin' fortune and can REALLY be reused five+ > times then by all means sell it to NASA. > > Of course there's always the Rutan solution - nitrous > oxide and ground-up tire rubber :-) Works just fine for the mission requirements. That's one of the signs of good economics and engineering. Use the cheapest engine that meets requirements. >>Intact abort is a good thing. It helps solve a lot of nagging problems >>with >>expendables independent of the whole launch cost thing. > > As I said, TOTALLY intact abort is almost certainly a pipe dream. > Damn the boosters - SAVE THE PAYLOAD ! Satellites (and people) > are EXPENSIVE. Funny, the shuttle design seems to include several intact abort modes that save the crew and the payload. There are, unfortunately, a few other abort modes that end with the crew bailing out, so the orbiter and payload would be toast if you can't make it back to a runway. People aren't that expensive compared to a billion dollar payload. This is true in many industries besides space travel. Take construction as an example. On a challenging billion dollar construction project, it's likely you're going to kill some number of workers due to accidents, so you buy insurance. The insurance companies know very well how much a person's life is worth, since they're the ones who typically pay out on such claims and they're not in the business of losing money. Part of the reason we've got billion dollar payloads is that launch costs are so high. That drives you towards bigger payloads that absolutely have to work right the first time. Smaller, cheaper launches would drive payloads the other way. And by cheaper, I mean at least an order of magnitude cheaper. Small changes in launch costs won't change payload design much. Jeff -- "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety" - B. Franklin, Bartlett's Familiar Quotations (1919) Quote
Guest Jeff Findley Posted July 20, 2007 Posted July 20, 2007 "Alan Anderson" <aranders@insightbb.com> wrote in message news:aranders-F53E5D.00025820072007@news.isp.giganews.com... > bw@barrk.net (Blackwater) wrote: > >> As with much machinery, 'robust' means "heavy". A reusable >> rocket engine has to resist a series of pressure, temperature >> and vibration extremes. That means the parts have to be built >> extra strong - and thus extra heavy. Weight is a VERY important >> consideration in space flight. Every ounce in the booster is >> another precious ounce of cargo you can't take with you. > > If you're worrying about ounces of cargo, you're focusing on the wrong > thing. Heavy is fine; it just takes fuel to compensate for it, and > fuel is cheap . > > Weight should NOT be as important as you are making it. What's > important is COST (oh, and reliability). A lot of the time, it's easier to make parts cheaper and more reliable by adding a bit more weight to the design. A some bleeding edge aerospace part designs use exotic machining processes to make them, like chemical milling and the like. If your focus is cost, you look for parts where you can eliminate the exotic processes and accept the weight growth. But your typical aerospace engineering process doesn't work this way. Look at the CEV and Ares I problems. They're very focused on weight reduction, which pushes you towards these lighter, more expensive, parts. The whole thing smacks of the tail wagging the dog since NASA seems hell bent on using SRB's in their new launchers. The limits of the five segment SRB design is driving everything else due to weight constraints. Jeff -- "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety" - B. Franklin, Bartlett's Familiar Quotations (1919) Quote
Guest Blackwater Posted July 20, 2007 Posted July 20, 2007 This has become insanely long, trying to cover too many subjects - so I'm going to snip everything and try to respond to a few of your (pretty good) points. Clearly we have a different idea as to what adds up to cheap & reliable. I like simply-designed single-use boosters, intended from the start as such - and prefer to use a lot of SRBs to provide a large percentage of the initial oomph. You prefer the idea of reusable liquid-fueled boosters, sacrificing a considerable amount of simplicity and up-front money to achieve said reusability. We're not sure HOW reusable they have to be however ( 5, 10, 50 times ? ) to make it worth it. Liquid-fueled boosters are vastly more complex machines than SRBs. However, with good, sane, design they're not necessarily less reliable. They have a few great advantages, throttleability plus the ability to shut them down entirely in case of emergency. IF we went with a "Russian" approach and used clusters of rather small engines, they'd be just fine for almost every purpose. Bigger engines are more expensive, and more prone to stress/vibration cracks in the combustion chamber. They also comprise a larger percentage of the total thrust, so losing one of three or five is a big deal while losing one of ten small engines is (usually) not. Bigger engines also require more robust mounting to deal with the thrust and vibration. SRBs are "Light 'em and hang on to your ass" engines. No control to speak of. Beautifully simplicit though. It IS possible to "shut down" an SRB of course ... by running a tube of explosive up one side. Press the button and the casing is ripped open, leaving you with burning 'powder' but not much pressure. It's even possible to cheat and formulate a propellant that ONLY burns above a certain pressure level (the initial pressure provided by an 'igniter' layer of more conventional propellant). I also once heard someone speak of a quasi-SRB design that employed a small tank of catalyst - with the fuel being formulated so it wouldn't burn without the catalyst present. Turn off the catalyst and the engine just quits. N2O-fueled 'solids' are a variation on this theme, but one where there's no oxidizer IN with the solid fuel at all (thus limiting efficiency). In any case, once thrust is no longer an issue it's much easier to kick the things loose in an emergency. (such a pity N20 is only 30% oxygen by weight - but there's always nitrogen tetroxide or HNO4) Now we get into "political" realities. Up-front costs are harder to justify than 'maintenence' costs. If your liquid boosters cost 50-mil each, while solids cost 5-mil each, the politicians can buy several solids and say "See ! We got the thing off the ground for only 5-mil !". I fear the public has totally lost faith in claims of 'reusability' after being so badly burned by the shuttle program. While the 5-mil may be 5-mil ten times a year every year, it still SEEMS cheaper somehow. So, even if reusables COULD be considerably cheaper in the long term, will anybody BELIEVE it enough to put money into the things ? Apparently not - the new toys are disposables and made to use varying numbers of SRBs to help things along. In politics, appearances are often more real than reality itself, so they went the "cheap" route with disposables. Oh yea ... then there's the final political reality in 'capitalist' republics - large govt programs have to be designed to enrich big industrial interests. So, if you can make the public BELIEVE it's saving money, while actually sending MORE money to industrial interests each year, you're golden and have earned your kickbacks and campaign donations. In truth, well-refined liquid-fueld boosters can indeed be "better" and far more reusable than SRBs. They too can be built in any size, even designed as small 'accessory power units' and strapped to a main booster just like SRBs. As a bonus they produce more thrust per pound of booster - solid fuels didn't even become practical until gunpowder went out and was replaced by new high-energy compounds. I don't think a "gunpowder" rocket can even achieve orbit - the fuel is too heavy in proportion to the thrust produced. Anyway, what I'm saying is that (within certain parameters) you're right about reusable liquids. BUT, are they realistic given the political system ? In the USA, the answer is "no". In China, perhaps "yes". Europe ... well, who knows about the euros ... to date they haven't put much into reusable systems. IF we get well-financed commercial ventures then we're far more likely to see reusable components from the boosters on up. Eventually, the public will gain faith in this technology and demand government use it too. Still, those well-financed commercial ventures had better be VERY well financed ... because 'reusable' has a much higher up-front cost. It's a serious investment, and one you won't recoup for many years. .. . . Oh, when I was talking 'boost phase abort' and 'total recovery' I was speaking about the ENTIRE rocket, not just the cargo capsule. Trying to land a half-fueled booster is VERY risky, and the bigger it is the harder it is to land it softly, without exploding. This is why I said to concentrate on saving the payload, not the boosters. .. . . In any event, I'm not "against" you and your perspective on things - technically you're perfectly correct. The question is whether you're "politically correct". Here, today, no. Tomorrow ... maybe. Meanwhile, disposables and SRBs ARE adequate for the next phase of space exploration, but if we try to go beyond, to 'exploitation', profitibility, then they're not good enough. Quote
Guest Fred J. McCall Posted July 20, 2007 Posted July 20, 2007 bw@barrk.net (Blackwater) wrote: : :Liquid-fueled boosters are vastly more complex machines :than SRBs. However, with good, sane, design they're not :necessarily less reliable. They have a few great advantages, :throttleability plus the ability to shut them down entirely :in case of emergency. : They have a couple of other advantages. As I understand it, they tend to be 'kinder' to the payload (less vibration from liquids than from solids - not sure exactly why that would be, but I do recall it being put forward). Not only are they at least as reliable as solids, but their failure modes tend to be more benign. When solids fail it's usually very fast and ends with a big bang. When liquids fail, there's usually some advance warning of what it going on. : :It's even possible to cheat and formulate a propellant :that ONLY burns above a certain pressure level (the :initial pressure provided by an 'igniter' layer of more :conventional propellant). I also once heard someone speak :of a quasi-SRB design that employed a small tank of :catalyst - with the fuel being formulated so it wouldn't :burn without the catalyst present. Turn off the catalyst :and the engine just quits. : :N2O-fueled 'solids' are a variation on this theme, but :one where there's no oxidizer IN with the solid fuel at :all (thus limiting efficiency). In any case, once thrust :is no longer an issue it's much easier to kick the things :loose in an emergency. : :(such a pity N20 is only 30% oxygen by weight - but :there's always nitrogen tetroxide or HNO4) : Once you start trying to 'tinker' solids to do away with the thrust termination issue you are also making things more complex and adding more cost and more failure modes. My view is that we should never use solids when launching people. My current opinion is that small reusables (which ought to be easier than big ones, for some reasonable values of 'small' and 'big') are what we ought to be aiming for for people and small cargo deliveries. Big cargos, satellites, etc, probably belong on expendables for the foreseeable future. -- "The reasonable man adapts himself to the world; the unreasonable man persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." --George Bernard Shaw Quote
Guest Rand Simberg Posted July 22, 2007 Posted July 22, 2007 On Thu, 19 Jul 2007 10:49:29 GMT, in a place far, far away, bw@barrk.net (Blackwater) made the phosphor on my monitor glow in such a way as to indicate that: >>>>> Show me how to build a reusuable vehicle that ISN'T >>>>> burdened-down by it's own complexity and requirements >>>>> for reusability and I'll consider modifying my assessment. >>>> >>>>There is nothing wrong with complexity. A modern airliner is quite >>>>complex. The primary difference between an air transport and a space >>>>transport is the much higher fllight rate of the former. >>> >>> Um ... it's a little more involved than that. >>> >>> Think about it for a while. >> >>Believe me, I've thought about it a great deal. As an aerospace >>professional, I've even been paid to think about it, and published >>papers on it. Have you? > > > Clearly I should be ... <laughing> And yet you are not. You might want to consider why. > Paid to write sci-fi plots eh ? No. > Multiusable do-everything launch & mission vehicles > are guarenteed to be too complex, too bulky and too > expensive. Who said anything about "do-everything launch & mission vehicles"? Work on your reading comprehension. And once again, you're stuck on the Shuttle, which is barely relevant to the discussion. > They are NOT "jetliners with rockets" by > ANY stretch of the imagination. Who said they are? Work on your reading comprehension. > Given the current > technology (and political system) if you want economy > and reliablity you go with standardized, modular, > one-time-use components, heavy on the SRBs. NASA > seems to agree and has put its money down for > just that. Yes, and it's wasting the taxpayers' money once again. Quote
Guest Blackwater Posted July 22, 2007 Posted July 22, 2007 On Sun, 22 Jul 2007 16:53:50 GMT, simberg.interglobal@org.trash (Rand Simberg) wrote: >On Thu, 19 Jul 2007 10:49:29 GMT, in a place far, far away, >bw@barrk.net (Blackwater) made the phosphor on my monitor glow in such >a way as to indicate that: > > >>>>>> Show me how to build a reusuable vehicle that ISN'T >>>>>> burdened-down by it's own complexity and requirements >>>>>> for reusability and I'll consider modifying my assessment. >>>>> >>>>>There is nothing wrong with complexity. A modern airliner is quite >>>>>complex. The primary difference between an air transport and a space >>>>>transport is the much higher fllight rate of the former. >>>> >>>> Um ... it's a little more involved than that. >>>> >>>> Think about it for a while. >>> >>>Believe me, I've thought about it a great deal. As an aerospace >>>professional, I've even been paid to think about it, and published >>>papers on it. Have you? >> >> >> Clearly I should be ... > ><laughing> > >And yet you are not. You might want to consider why. Poor poltical connections, of course. Now if I was "Skull & Bones" ..... :-) >> Paid to write sci-fi plots eh ? > >No. Pity. A lot of money in those ... >> Multiusable do-everything launch & mission vehicles >> are guarenteed to be too complex, too bulky and too >> expensive. > >Who said anything about "do-everything launch & mission vehicles"? That was what they tried to make the shuttle. And failed. >Work on your reading comprehension. And once again, you're stuck on >the Shuttle, which is barely relevant to the discussion. > >> They are NOT "jetliners with rockets" by >> ANY stretch of the imagination. > >Who said they are? Work on your reading comprehension. Sorry, but you DID imply that in terms of complexity shuttles and their launch system aren't much different than commercial airliners ... >> Given the current >> technology (and political system) if you want economy >> and reliablity you go with standardized, modular, >> one-time-use components, heavy on the SRBs. NASA >> seems to agree and has put its money down for >> just that. > >Yes, and it's wasting the taxpayers' money once again. Um ... yes - BUT the taxpayers wouldn't have gone for the MUCH higher up-front costs of a highly-resusable all-liquid fueled system. In short, they decided to HAVE a space program. Assuming the program returns things of value, then it's not "wasting the taxpayers money". So, your way = no program ... money spent bombing Afghanistan. My way = space program ... but with somewhat high monthly payments. Choose. Quote
Guest Rand Simberg Posted July 22, 2007 Posted July 22, 2007 On Sun, 22 Jul 2007 19:37:31 GMT, in a place far, far away, bw@barrk.net (Blackwater) made the phosphor on my monitor glow in such a way as to indicate that: >>>>Believe me, I've thought about it a great deal. As an aerospace >>>>professional, I've even been paid to think about it, and published >>>>papers on it. Have you? >>> >>> >>> Clearly I should be ... >> >><laughing> >> >>And yet you are not. You might want to consider why. > > > Poor poltical connections, of course. No, I have no "political connections." It's because you have no experience or credentials, and don't know what you're talking about. >>> Multiusable do-everything launch & mission vehicles >>> are guarenteed to be too complex, too bulky and too >>> expensive. >> >>Who said anything about "do-everything launch & mission vehicles"? > > > That was what they tried to make the shuttle. And as I said, the Shuttle has very little to do with reusable vehicles in general. Why do you persist in this logical fallacy? >>> They are NOT "jetliners with rockets" by >>> ANY stretch of the imagination. >> >>Who said they are? Work on your reading comprehension. > > Sorry, but you DID imply that in terms of complexity > shuttles and their launch system aren't much different > than commercial airliners ... I said, and implied, nothing about "shuttles." >>> Given the current >>> technology (and political system) if you want economy >>> and reliablity you go with standardized, modular, >>> one-time-use components, heavy on the SRBs. NASA >>> seems to agree and has put its money down for >>> just that. >> >>Yes, and it's wasting the taxpayers' money once again. > > Um ... yes - BUT the taxpayers wouldn't have gone for the > MUCH higher up-front costs of a highly-resusable all-liquid > fueled system. I know I wouldn't have. NASA is not competent to develop a low-cost launch vehicle of any design. > In short, they decided to HAVE a space program. No, they decided to have a jobs program. Quote
Guest Einar Posted July 22, 2007 Posted July 22, 2007 Blackwater wrote: > On Wed, 18 Jul 2007 08:33:47 -0400, "Jeff Findley" > <jeff.findley@ugs.nojunk.com> wrote: > You act as if they're lagging behind intentionally. The USA > might, "porkbarrel politics", but not any of the others. > > I fear the real exploitation of space will ONLY become possible > when some drastically new propulsion technology appears. I say > 'warp drive', but that probably won't work. Higher dimensions, > inertia-reduction, funky quantum tricks ... we'd better find > SOMETHING or we're STUCK on this increasingly small and crowded > ball of rock. "Space" is simply uneconomic and looks to remain > uneconomic. There have been some exotic ideas mentioned, i.e. to use a groundlaser to beam something up. I Quote
Guest Einar Posted July 22, 2007 Posted July 22, 2007 Blackwater wrote: > On Wed, 18 Jul 2007 10:01:34 -0400, "Jeff Findley" > <jeff.findley@ugs.nojunk.com> wrote: > I'm saying that we NEED 'warp drive' or whatever to really > make space something viable, affordable and safe (enough). > I really don't think we're going to accomplish that with > conventional rockets - reusable or not. Of course we're > STUCK with them, for now, but we're likewise stuck with > all their problems and limitations. > > Someday somebody will come up with a propulsion system > better than spurting hot gas out the rear. A certain > amount of money SHOULD be allocated to fund the kinds > of theorists interested in such things. As the work > will be 99.9% mental, it won't be expensive - just > enough to keep a dozen or two PhDs from starving. What about gravitics? If they prove that the Higgs boson transmits gravity, meaning they finally manage to force it briefly into being in that Big Hadron Collider, might that not lead towards gravitics technology? After all, they already can make anty hydrogen. Why not gravity, if they can make enough of that Higgs boson? Gravitic drive would be the final spacedrive, i.e. acceleration/ deceleration without fuel burn. Cheers, Einar Quote
Guest Fred J. McCall Posted July 22, 2007 Posted July 22, 2007 bw@barrk.net (Blackwater) wrote: :On Sun, 22 Jul 2007 16:53:50 GMT, simberg.interglobal@org.trash (Rand :Simberg) wrote: : :>On Thu, 19 Jul 2007 10:49:29 GMT, in a place far, far away, :>bw@barrk.net (Blackwater) made the phosphor on my monitor glow in such :>a way as to indicate that: :> :> :>>>>>> Show me how to build a reusuable vehicle that ISN'T :>>>>>> burdened-down by it's own complexity and requirements :>>>>>> for reusability and I'll consider modifying my assessment. :>>>>> :>>>>>There is nothing wrong with complexity. A modern airliner is quite :>>>>>complex. The primary difference between an air transport and a space :>>>>>transport is the much higher fllight rate of the former. :>>>> :>>>> Um ... it's a little more involved than that. :>>>> :>>>> Think about it for a while. :>>> :>>>Believe me, I've thought about it a great deal. As an aerospace :>>>professional, I've even been paid to think about it, and published :>>>papers on it. Have you? :>> :>> :>> Clearly I should be ... :> :><laughing> :> :>And yet you are not. You might want to consider why. : : : Poor poltical connections, of course. : : Now if I was "Skull & Bones" ..... :-) : I'd put it down to your 'poor neural connections', myself... : :>> Paid to write sci-fi plots eh ? :> :>No. : : Pity. A lot of money in those ... : Don't know much about writing, either, I see... : :>> Multiusable do-everything launch & mission vehicles :>> are guarenteed to be too complex, too bulky and too :>> expensive. :> :>Who said anything about "do-everything launch & mission vehicles"? : : : That was what they tried to make the shuttle. : : And failed. : Yep. And WHY did they fail? Because they accepted excessively high operating costs to keep the development costs down. : :> :>Work on your reading comprehension. And once again, you're stuck on :>the Shuttle, which is barely relevant to the discussion. :> :>> They are NOT "jetliners with rockets" by :>> ANY stretch of the imagination. :> :>Who said they are? Work on your reading comprehension. :> : : Sorry, but you DID imply that in terms of complexity : shuttles and their launch system aren't much different : than commercial airliners ... : Where did he do that? : :> :>> :>> Given the current :>> technology (and political system) if you want economy :>> and reliablity you go with standardized, modular, :>> one-time-use components, heavy on the SRBs. NASA :>> seems to agree and has put its money down for :>> just that. :> :>Yes, and it's wasting the taxpayers' money once again. :> : : Um ... yes - BUT the taxpayers wouldn't have gone for the : MUCH higher up-front costs of a highly-resusable all-liquid : fueled system. In short, they decided to HAVE a space program. : Assuming the program returns things of value, then it's not : "wasting the taxpayers money". : : So, your way = no program ... money spent bombing Afghanistan. : : My way = space program ... but with somewhat high monthly payments. : : Choose. : If those are the only two choices, I choose the first one rather than another program that just eats up money and shows how it CAN'T be done... You want to repeat the same mistake that was made with the Shuttle. Many of the rest of us have learned that when it hurts you should stop doing it. Of course, your little exercise in the fallacy of the excluded middle is irrelevant, since those are NOT the only two choices. -- "The reasonable man adapts himself to the world; the unreasonable man persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." --George Bernard Shaw Quote
Guest Einar Posted July 22, 2007 Posted July 22, 2007 Blackwater wrote: > On Wed, 18 Jul 2007 10:23:45 -0700, "Bill Bonde ( 'Hi ho' )" > <tributyltinpaint@yahoo.co.uk> wrote: > > > > > > >Blackwater wrote: > >> > >> On Tue, 17 Jul 2007 09:27:45 -0600, Joe Strout <joe@strout.net> wrote: > >> > >> >In article <469cb0b4.4766375@news.east.earthlink.net>, > >> > bw@barrk.net (Blackwater) wrote: > >> > > >> >> It's actually ILLEGAL for Brits to fly into space. > >> >> ... > >> >> Apparently the government implemented the policy long ago, > >> >> assuming it would prevent aerospace resources from being > >> >> "wasted" on human flight. > >> > > >> >It'll be interesting to see them try to haul Branson off to jail after > >> >the maiden Virgin Galactic flight. > >> > >> He will probably be THE case ... the one that > >> finally gets the law changed - and he damned > >> well has the money, lawyers and status to do it. > >> > >I suspect anyone who has the money to get into space would be enough to > >get such a law changed. > > Branson has two other things going for him - his charisma > and general British Pride in a local boy who's done so well. > A snobby SOB who inhereited daddys money wouldn't have it > so easy. Branson is more than a businessman, he's a celebrity > and hero-figure. (yes, 'idiot-figure' to those who distain > dangerous adventures, but those are a minority) It will probably take a buiness man visionary to create passenger spacetravel. Cheers, Einar Quote
Guest Einar Posted July 22, 2007 Posted July 22, 2007 Blackwater wrote: > On Wed, 18 Jul 2007 14:43:19 -0400, "Jeff Findley" > <jeff.findley@ugs.nojunk.com> wrote: > > > > >"Blackwater" <bw@barrk.net> wrote in message > >news:469e35f5.7727078@news.east.earthlink.net... > >> On Wed, 18 Jul 2007 10:01:34 -0400, "Jeff Findley" > >> <jeff.findley@ugs.nojunk.com> wrote: > >> > >>> > >>>"Blackwater" <bw@barrk.net> wrote in message > >>>news:469e0eb6.6752038@news.east.earthlink.net... > >>>> On Wed, 18 Jul 2007 08:33:47 -0400, "Jeff Findley" > >>>> <jeff.findley@ugs.nojunk.com> wrote: > >>>> > >>>>> > >>>>>"Blackwater" <bw@barrk.net> wrote in message > >>>>>news:469d19a5.31631187@news.east.earthlink.net... > >>>>>> Geez ... we REALLY need 'warp drive' or something. > >>>>>> Reaction rockets are just TOO ... expensive, bulky, > >>>>>> inefficient and dangerous. > >>>>> > >>>>>Not really. > >>>> > >>>> Really ? > >>>> > >>>> Go build a big rocket and see what it does > >>>> to your bank balance. > >>>> > >>>>>What we really need is to stop throwing away the rockets after > >>>>>every flight. > >>>> > >>>> Sounds great - but it never seems to work out in practice. > >>>> The stresses of operation and plunging back again combined > >>>> with the need for lightweight components ... well ... I > >>>> wouldn't want to ride a re-used booster. > >>>> > >>>>> Maybe start with a fully reusable first stage then work up to > >>>>>a fully reusable upper stage, giving a fully reusable TSTO. > >>>> > >>>> Bert Rutan may have come up with a viable fix - use some > >>>> kind of aircraft as the "1st stage". Nowdays it can be fully > >>>> robotic, autopiloted. A big wing with engines optimized for > >>>> high altitudes and you can cut the first 60,000 feet off > >>>> your trip. > >>>> > >>>> Use a simple SRB as the '2nd stage'. Save the expensive stuff > >>>> for the final orbital-insertion stage. > >>>> > >>>> It would be a help ... but it wouldn't add-up to anywhere > >>>> near the necessary order-of-magnitude price reduction needed > >>>> to properly commercialize space. Scramjet-powered orbital > >>>> air/spacecraft - someday, maybe ... > >>>> > >>>>>> Got to knock at least > >>>>>> an order of magnitude off the price to orbit. If > >>>>>> you know any physics geniuses, buy 'em a few beers > >>>>>> and then give 'em a mission before they're sober > >>>>>> enough to change their minds. > >>>>> > >>>>>It ought to be possible to knock more than an order of magnitude off by > >>>>>focusing on making launch vehicles reusable and more efficient to turn > >>>>>around between flights. > >>>> > >>>> I don't believe it. > >>> > >>>Why not? Airliners aren't expendable. > >> > >> NOT the same animal, NOT the same jungle. Spacecraft have > >> to be built much lighter, more fragile, and then are > >> sujected to extreme accelerations, vibrations, thermal > >> distortions and corrosive chemicals. > > > >So what. Just because they're not exactly the same animal doesn't mean that > >there isn't room for improvement with rockets. Throwing away your engines > >on each and every flight is more than a bit silly if your long term goal is > >to reduce reoccuring launch costs. > > SURE there's room for improvement. But how MUCH improvement ? > > As for the economy of reusable engines, I dunno about that. > Something built to give it's all for a one-time event, and > be nothing but a burnt-out shell afterwards, may indeed be > cheaper than something built robustly enough to be used > dozens of times. Not to mention that by the time you get > to use #23 ... well ... kind of like driving cross-country > in a '72 Pontiac with 129,000 miles on the odometer - except > if your rocket engine fails you DIE rather than just being > stuck in Utah. > > As with much machinery, 'robust' means "heavy". A reusable > rocket engine has to resist a series of pressure, temperature > and vibration extremes. That means the parts have to be built > extra strong - and thus extra heavy. Weight is a VERY important > consideration in space flight. Every ounce in the booster is > another precious ounce of cargo you can't take with you. > > To enhance reusability, "complexity" may also be involved. > Fancier cooling schemes, more redundancy. Every time you > add an element that might interact with another element > you add "complexity" and greatly increase the chances of > an unexpected interaction. Beyond a point, you gain very > little by adding more "complexity" - and then start to go > downhill in terms of reliability. > > Now, instead, consider the single-use booster. SRBs are old hat > and - if you design any joints properly - about as simple and > reliable as you can get. Nothing to them. For a single-use liquid- > fueled engine it should be possible to make use of some of the > newer carbon-fiber or carbon nanotube composites to give the > combustion chamber mechanical strength. Weight is decreased. > You only need a thin inner layer of metal into which you stamp > your channels for fuel and oxidizer. That inner lining, AND > the composites, will be "cooked" by the time the burn is finished. > Can't use them again - but then they didn't COST much and didn't > WEIGH much. > > Does the lower cost and weight stand up against the hypothetical > 24 reuses of the 'robust'/complex engine ? Maybe ... especially > if you understand that the 'robust' engine may NOT quite live > up to it's projected lifespan before going boom . Also, those > 'robust' engines are a considerable "investment" - time and money. > If you find they're not quite what you wanted, you're still kind > of STUCK with them for awhile. The cheaper, simpler engines are > not such a great investment, you can specify changes when you > order the next half-dozen. > > >>>It's part of the reason we can > >>>justify the extreme costs to develop, build, and fly super efficient high > >>>bypass turbofan engines for them. The other big reason is the huge demand > >>>for passenger air travel. > >> > >> Actually, the passengers fly for "free" - it's the CARGO > >> under their feet that generates the profits. > > > >Then lets add the huge demand for fast cargo transport as a reason the jet > >engine companies keep eeking out more performance for less fuel out of next > >generation engines. > > Hell yes ! > > It's dollars per pound/mile ... whether the pounds > represent people or FedEx packages. A one-percent > improvement in fuel economy translates into many > millions of dollars per year. An extra ten knots > of speed means FedEx gains x-many minutes per month > in which to deliver packages - so it can thus > handle MORE of them. > > >>>> It would require a DRASTIC simplification of the design, so > >>>> fewer things could go wrong and fixes would be quick cheap > >>>> and easy. Nobody seems able to do that, not America, not > >>>> Russia, not China, not Japan, not France. If anything, > >>>> designs have just become MORE complex and fragile. > >>> > >>>I doubt it. In many ways a reusable is far more complex than an > >>>expendable. > >>>You justify this complexity, and cost, by flying it more than once. > >> > >> But the complexity works AGAINST you trying to re-use the > >> component. Every component interacts with many others, it > >> quickly gets out of hand. Why do you think there are so > >> often last-second delays launching shuttles ? ALL those > >> little parts have to be tweaked, for a few minutes, into > >> harmonious operation. They can BARELY do it. Actually, they > >> CAN'T do it ... they just fudge on the safety parameters > >> and launch anyway. > > > >Why use the shuttle as an example. As I said before, it's clear to everyone > >who's looked at the shuttle that serious design compromises were made during > >development which decreased development costs but greatly increased > >reoccuring costs. Design the next reusable vehicles for true reusability > >and do it with current technology. Technology has come a long way since the > >early 70's. > > But the political/economic factors which caused all > the 'compromises' in the shuttles design STILL exist. > The next shuttle will STILL be designed by committee, > and that result passed through other committees and > finally through committees of self-interested politicians > who will want all kinds of changes in design and manufacture > as so to direct as much money as possible into their state > and their contributors pockets. "Shuttle-II" will be just > as much of a mess as the existing STS. > > Note too that they REALLY tried to build the shuttles SRBs > so they could be re-used. Alas, between the heat and vibration > and smacking into the ocean ... the things were trash after > the first use. IMHO, forget re-usable boosters. Just build > the cheapest, lightest, simplest single-use units possible. > > >>>> As for "efficiency" ... rocket efficiency isn't going to > >>>> increase much. It's the physics. Recovery/repair/reuse > >>>> efficiency COULD improve considerably, but then we still > >>>> need robust and simplistic designs to make that possible. > >>> > >>>Time for a reality check. > >> > >> Been there, checked-in. Waiting for you to show up :-) > >> > >> USA porkbarrel politics work against efficiency and > >> simplicity - but this isn't the case in the other > >> spacefaring countries. If France or Russia COULD do > >> it all that more cheaply and better they WOULD have. > >> The observable reality says "This is as good as it gets". > > > >Neither is willing to spend the big bucks necessary for development of > >reusable launch vehicles big enough to replace their existing launchers when > >they're still making money on their expendables. Actually, Russia barely > >has money to keep flying their existing expendables, nevermind developing > > anything new. I don't think porkbarrel politics has much to do with it. > > France is much more "socialist" than the USA. If cost-savings > through reusability could be persuasively argued the govt would > get the industy to switch - and not take too much profit from > the excercise. > > Russia, for now, is indeed too poor to switch horses. Their > existing system works very well so there's little motivation > for a big investment in newer or reusable technology. However > in the 1970s, the USSR still did have some spare cash and an > iron grip on industry. If reusable had sounded good then, they > could have gone that way a LOT quicker than 'democratic' nations. > They didn't. > > China, for now, is essentially copying Russian technology. > However it DOES have great wads of cash and sees a spacefaring > future for itself. Expect them to do something spectacular a > lot sooner than we, or their propaganda bureau, predicts. > Either a moon landing or a BIG space-station (they've been > very interested in benifits of inflatable structures). With > that kind of future in mind, you'd expect them to be keen > on reusable boosters and such. So far however, they do not > seem all that interested. > > >>>The cost of fuel and oxidizer for a launch vehicle is absolutely tiny > >>>compared to overall launch costs. I personally like LOX/kerosene since > >>>both > >>>are widely available and the kerosene is pretty dense. > >> > >> Agreed and agreed ... it's not the fuel (even though LOX requires > >> a lot of energy to make and a lot of care to handle). It's the > >> MACHINE the fuel goes into. > > > >A machine that's typically thrown away after each and every flight. > > Boosters INTENDED for a single use are relatively simple > and inexpensive. It's the damned shuttle ... we got all > the bulk, complexity and expense associated with reusability, > but only the actual shuttles get reused. Even then, the > engines and several other systems need a major overhaul > after each flight. > > >> It's the highly-trained PEOPLE required > >> to make sure everything's right. > > > >Parly required because every flight of an expendable is of an unflown > >vehicle. The full up test flight is the flight the customer paid for. > > > >> It's the huge FACILITIES and > >> INFRASTRUCTURE required to support everything. > > > >Sure, and a lot of that is to build the vehicles in the first place, then > >you throw the vehicle away and build yet another vehicle. > > > >> If these were > >> private ventures you'd also have to add INSURANCE to the mix. > > > >Of course, but the hope is that reusables will have intact abort modes, so a > >launch failure would mean you have to recover the payload and try again. > >With many expandable launch failures, you not only have to build a new > >launch vehicle to try again, but you also have to build a new payload as > >well. Which type of failure costs the insurance company more money, which > >is passed on to its customers as higher insurance premiums? > > An boost-phase abort mode ??? That would mean soft-landing > a big tank, possibly with a fire at one end, of liquid > oxygen and something extremely flammable in a desert. > I sure as hell wouldn't go NEAR the thing ... :-) > > IMHO, you'd have to sacrifice the boosters and plan to > recover only the payload. As the payloads often cost > more than the rest of the vehicle combined, this makes > good sense. I'm suprised the new Ariane isn't set up > to pop away the cargo capsule on a milliseconds notice. > > >> Rockets are still essentially custom-made one-off machines. > >> There's no assembly line, no grand template, no army of > >> industrial robots, no real "standard components". This makes > >> them incredibly expensive. Dealing with every issue the > >> engineers know about or can imagine makes them insanely > >> complex and expensive. This can't change unless designs > >> are somehow simplified and sufficient VOLUMES of a 'standard > >> rocket' are ordered so that assembly-line economics CAN > >> begin to have an effect. > > > >Large aircraft assembly processes are fairly similar to launch vehicle > >assembly processes. They're very expensive to make, so we simply don't > >throw them away after every flight. In fact, many aircraft fly for decades, > >being demoted to cargo only flights or to be sold off to foreign countries > >who continue to fly them for many more decades. You just don't throw away > >such an expensive asset when you're done with it. > > As I said to someone ... rockets ain't airplanes, either > in design or in their economics. > > However - by simplifying design, using standardized components > and 'modular' systems, you COULD gain some of the advantages > of assembly-line economics. NASAs next toys are kind-of like > that, though I doubt they took "simplify" to heart (doesn't > profit as many contractors & politicians). > > >>>The Saturn V first > >>>stage burned something like 200,000 gallons of "rocket grade" kerosene > >>>(RP-1). If you're paying $5 per gallon for your kerosene, that's only $1 > >>>million dollars per launch. That's a pitiful fraction of the overall > >>>costs > >>>for an expendable Saturn V launch. And LOX is extremely cheap, litterally > >>>pennies per pound, in industrial quantities since air is the raw material > >>>you start with. One astronautix.com page says NASA was paying $0.08 per > >>>kg > >>>in the 1980's for LOX. > >>> > >>>Clearly, it's not physics that dictates the cost since the fuel and > >>>oxidizer > >>>needed are relatively cheap. > >> > >> The physics I was speaking of relate to how much bang you > >> can get out of a rocket engine of a given size. It's a > >> function of ignition-chamber pressure, subsequent gas > >> expansion and velocity plus the weight of the components. > >> X-energy IN, Y-energy translated into thrust. > >> > >> Hasn'tchanged much since the 60s. It defines the vehicle/cargo > >> weight ratio. > > > >You're missing the point. With the cost of fuel so low, why is the > >vehicle/cargo weight ratio important ? Why not optimize the design for the > >lowest cost per lb of cargo to LEO? It's a different optimization > >constraint which will drive you towards a completely different design than > >the "performance uber alles" philosophy of the LOX/LH2 crowd. > > Fuel is more than weight, it's BULK. Low-effeciency engines > mean your booster has to carry more fuel and be physically > LARGER to accomodate it. Large uses more materials. Large > introduces more vibrational modes. Larger means more surface > area for your cyro tanks - and therefore thermal expansion/ > contraction and thus more insulation and therefore more > weight and so on and so forth. > > You really want your rocket to be as small as possible. Thus, > you want high efficiency engines. Materials and heat dissipation > limit your chamber pressures. You can go for bigger chambers > but now you've got to use bigger fuel pumps. > > >> [snips] > >> > >> I prefer a completely DISPOSABLE vehicle. Build it to > >> make exactly ONE flight - build it simple. Designing > >> for re-use adds mass and complexity. It also locks you > >> into the one design. You've made your 'investment' and > >> now you're stuck. > > > >Tell that to the guys flying B-52's. They're definately not quite the same > >vehicles as when they were built. One of these days, the funding for > >upgrading the engines to turbofans will come through and they'll even look > >different on the outside. ;-) > > Yea, the '52 has certainly evolved - but then aircraft ARE > easier to modify. It's also easier to test each modification, > you'll only kill a few soldiers if it doesn't work ... > > >For that matter, look at the shuttle. There have been numerous upgrades > >over the years along with even more numerous proposed upgrades that were > >never funded. You certainly can refit existing airframes with newer > >technologies and keep flying them. > > You can refit - but WITHIN LIMITS. They're not going to alter > the shuttles external profile or major structural components. > There's only so much room for certain kinds of components. The > overall weight and balance can't change much. They're not going > to completely re-wire it. > > Anyhow, I don't have much against reusable mission vehicles. > Not much anyway. I'm more concerned with the boosters. Even > thus, for many kinds of missions, a more conventional "capsule" > would serve ... and you can throw it away later. You can make > several kinds of capsules, each optimized for a specific kind > of job. I think this would actually be cheaper and better than > trying to build a does-it-all machine. > > >> The easiest 'disposable' route for spacecraft is to make > >> maximum use of SRBs. Alone, or combined with LFRs so a > >> range of thrust adjustment is possible, they're really > >> a good way to add oomph without adding much cost. Not > >> much more than a tube packed with 'powder'. > > > >Only if you like paying for entirely new vehicles after each and every > >flight and will accept the cost and safety issues which arise from flying > >expendables. > > The safety issues are managable. The single one the shuttle > program has failed to deal with is an incident where you > may have to detach the SRBs early on, while they're still > burning full power. This isn't too difficult to cope with, > it's just that the current framework isn't designed to > do the job. > > As for cost, SRBs do NOT have to be extremely expensive. > You KNOW we're getting ripped-off by Thiokol - but they've > managed to secure a position as sole shuttle SRB manufacturer > ( I wonder how they managed that ?). New launch systems open > the door to new bidders ... and, in theory, prices could be > negotiated down considerably. > > Oh, and remember what I said about the evils of "bigness" ? > That applies to SRBs too. The shuttles SRBs are difficult > to make because they're so large. The propellant is cast > in large 'pills' that really want to crack as they cure. > The tube assembly had to be multi-jointed ... and we know > what THAT caused. More, slimmer, SRBs may be the ticket. > > But, if you can come up with a really bare-bones liquid > booster that doesn't leak fuel all over the place, doesn't > cost a bleedin' fortune and can REALLY be reused five+ > times then by all means sell it to NASA. > > Of course there's always the Rutan solution - nitrous > oxide and ground-up tire rubber :-) > > >Intact abort is a good thing. It helps solve a lot of nagging problems with > >expendables independent of the whole launch cost thing. > > As I said, TOTALLY intact abort is almost certainly a pipe dream. > Damn the boosters - SAVE THE PAYLOAD ! Satellites (and people) > are EXPENSIVE. You do make good arguments to someone who has no expertiece in this particular field. It certainly sounds plausable that modular construction will reduce costs. Most certainly a single use booster is cheaper than a multiuse one. It will also be lighter and less complex. That is self evident. The only remaining issue is wether a multiuse booster can be used often enough for it to become worthwile regardless. That remains to be seen, and like you have pointed out the odds may be stacked against that happening at the current tech level. Still, I do hope that Kistler Aerospace can make it happen. But I have read the specs for theyr planned booster, it does indeed look bit big for the kind of payload it is going to take into orbit. It appears that each stage is carrying some extra fuel in order to fly back so that it will glide down not to far away. While that may reduce operational expenses that clearly does result in a big veicle which does have a relativelly small payload. Cheers, Einar Quote
Guest Einar Posted July 22, 2007 Posted July 22, 2007 Jeff Findley wrote: > "Blackwater" <bw@barrk.net> wrote in message > news:469fd78d.232031@news.east.earthlink.net... > > On Wed, 18 Jul 2007 14:43:19 -0400, "Jeff Findley" > > <jeff.findley@ugs.nojunk.com> wrote: > >>So what. Just because they're not exactly the same animal doesn't mean > >>that > >>there isn't room for improvement with rockets. Throwing away your engines > >>on each and every flight is more than a bit silly if your long term goal > >>is > >>to reduce reoccuring launch costs. > > > > SURE there's room for improvement. But how MUCH improvement ? > > > > As for the economy of reusable engines, I dunno about that. > > Something built to give it's all for a one-time event, and > > be nothing but a burnt-out shell afterwards, may indeed be > > cheaper than something built robustly enough to be used > > dozens of times. Not to mention that by the time you get > > to use #23 ... well ... kind of like driving cross-country > > in a '72 Pontiac with 129,000 miles on the odometer - except > > if your rocket engine fails you DIE rather than just being > > stuck in Utah. > > All (sane) liquid fuel rocket engines are reusable. Why? Because you want > safety margins. You typically design liquid fueled rocket engines for > multiple firings (it's often nice to test fire them before you use them) and > design them to last for firings far longer than what's needed for a single > mission. > > Take a look at the DC-X/XA program where RL-10 engines were routinely used > over and over without pulling them from the vehicle. > > > As with much machinery, 'robust' means "heavy". A reusable > > rocket engine has to resist a series of pressure, temperature > > and vibration extremes. That means the parts have to be built > > extra strong - and thus extra heavy. Weight is a VERY important > > consideration in space flight. Every ounce in the booster is > > another precious ounce of cargo you can't take with you. > > Rocket engines are already fairly robust, otherwise they'd tend to go "boom" > a lot more often than they do. Even the highly strung SSME has gotten to > the point where you don't have to tear it down after every flight to inspect > it and rebuild it. > > > To enhance reusability, "complexity" may also be involved. > > Fancier cooling schemes, more redundancy. Every time you > > add an element that might interact with another element > > you add "complexity" and greatly increase the chances of > > an unexpected interaction. Beyond a point, you gain very > > little by adding more "complexity" - and then start to go > > downhill in terms of reliability. > > Doubtful, as existing liquid fueled rocket engines are already reusable. > This is why throwing them away after every flight is so silly! > > >>Why use the shuttle as an example. As I said before, it's clear to > >>everyone > >>who's looked at the shuttle that serious design compromises were made > >>during > >>development which decreased development costs but greatly increased > >>reoccuring costs. Design the next reusable vehicles for true reusability > >>and do it with current technology. Technology has come a long way since > >>the > >>early 70's. > > > > But the political/economic factors which caused all > > the 'compromises' in the shuttles design STILL exist. > > The next shuttle will STILL be designed by committee, > > and that result passed through other committees and > > finally through committees of self-interested politicians > > who will want all kinds of changes in design and manufacture > > as so to direct as much money as possible into their state > > and their contributors pockets. "Shuttle-II" will be just > > as much of a mess as the existing STS. > > This is why we likely won't see reusable rocket stages emerging from "the > usual suspects". It's far more likely that they'll emerge from the > start-ups, who are currently focusing on suborbital tourism. The new market > of tourism is likely to change the plitical/economic status quo, since "the > usual suspects" are not involved. The market forces for tourism naturally > demand high flight rates, which drives you towards reusability. > > "The usual suspects" simply aren't that interested in high flight rates. > They tend to lean towards more payload on fewer flights, which results in > low flight rates. With such low flight rates, you simply cannot justify > reusable launch vehicles on economic grounds. > > > Note too that they REALLY tried to build the shuttles SRBs > > so they could be re-used. Alas, between the heat and vibration > > and smacking into the ocean ... the things were trash after > > the first use. IMHO, forget re-usable boosters. Just build > > the cheapest, lightest, simplest single-use units possible. > > They do clean them out and reuse them. It's just that solids are really bad > when it comes to reuse. It's a lot harder to refurbish them than it was to > fill up the DC-X/XA's tanks with more fuel and oxidizer and simply fly it > again. > > > > Boosters INTENDED for a single use are relatively simple > > and inexpensive. It's the damned shuttle ... we got all > > the bulk, complexity and expense associated with reusability, > > but only the actual shuttles get reused. Even then, the > > engines and several other systems need a major overhaul > > after each flight. > > Sorry, but much of the shuttle isn't reusable. Much of it is refurbished > and rebuilt after every flight. It's not a good example of a reusable > vehicle. The DC-X/XA is a far better example. > > >>Of course, but the hope is that reusables will have intact abort modes, so > >>a > >>launch failure would mean you have to recover the payload and try again. > >>With many expandable launch failures, you not only have to build a new > >>launch vehicle to try again, but you also have to build a new payload as > >>well. Which type of failure costs the insurance company more money, which > >>is passed on to its customers as higher insurance premiums? > > > > An boost-phase abort mode ??? That would mean soft-landing > > a big tank, possibly with a fire at one end, of liquid > > oxygen and something extremely flammable in a desert. > > I sure as hell wouldn't go NEAR the thing ... :-) > > Fire is possible, but more likey is a problem in the engine that would > require you to simply shut it down. You can shut down liquid engines quite > simply by shutting off valves to the engine. > > You design the thing with multiple engines. You design each stage to use 5 > engines at 80% maximum thrust. If you lose one engine, you throttle up the > others to 100% and continue the mission since you've not lost any > performance with one engine out. Some expendables have had this built in. > For example, the Saturn V's first and second stages could tolerate engine > outs at some points of the flight and still complete the mission. > > If you lose two out of five engines, then you've got an abort on your hands > only if it comes at a bad time. This is because you typically throttle your > engines back towards the end of the burn to keep g-loads down. At any rate, > say you lose two engines early on and simply don't have enough thrust to > complete the mission. You'd want to keep your remaining engines at 100% to > burn off all the fuel in the tanks, and then you land your reusable stage in > much the same way you would if it were a nominal mission. > > Making a vehicle reusable means you already have recovery systems built > into the stage. You use them during an abort to recover the stage, and the > payload if it's an upper stage. > > Note that the shuttle can, theoretically, do some of this, which is why > there are abort modes built into the system. Depending on the emergency, it > can abort to the launch site, to a trans-Atlantic site, or to orbit > (possibly too low to complete the mission, but high enough to give you > plenty of time to let you pick the safest landing site). > > > IMHO, you'd have to sacrifice the boosters and plan to > > recover only the payload. As the payloads often cost > > more than the rest of the vehicle combined, this makes > > good sense. I'm suprised the new Ariane isn't set up > > to pop away the cargo capsule on a milliseconds notice. > > Why? I'm assuming a reusable that can return a payload from LEO that's just > as big as the one it can launch, so there is no fundamental reason you can't > burn off any remaining fuel and make an emergency landing with the payload > intact. > > >>Large aircraft assembly processes are fairly similar to launch vehicle > >>assembly processes. They're very expensive to make, so we simply don't > >>throw them away after every flight. In fact, many aircraft fly for > >>decades, > >>being demoted to cargo only flights or to be sold off to foreign countries > >>who continue to fly them for many more decades. You just don't throw away > >>such an expensive asset when you're done with it. > > > > As I said to someone ... rockets ain't airplanes, either > > in design or in their economics. > > Funny how the DC-X/XA was operated much less like traditional rockets and > much more like a jet aircraft. After a flight they could quickly turn it > around and fly it again. There's nothing fundamenal which prevents you from > operating in this way. In fact, this was one of the big criticisms of > rocket engines before DC-X/XA, so quick turn around was one of its design > goals. This design goal was met and demonstrated during an actual test > flight prgram. > > >>You're missing the point. With the cost of fuel so low, why is the > >>vehicle/cargo weight ratio important ? Why not optimize the design for > >>the > >>lowest cost per lb of cargo to LEO? It's a different optimization > >>constraint which will drive you towards a completely different design than > >>the "performance uber alles" philosophy of the LOX/LH2 crowd. > > > > Fuel is more than weight, it's BULK. Low-effeciency engines > > mean your booster has to carry more fuel and be physically > > LARGER to accomodate it. > > Tanks are cheap. Making them bigger, in the design stage, doesn't add much > to the overall costs of the vehicle when you go to build it. > > > Large uses more materials. > > Materials are cheap compared to the overall program, especially when you > plan to use them for more than one flight. Look at the cost of the ET's for > the shuttle program. They're expendable because they're relatively cheap to > make. > > > Large > > introduces more vibrational modes. > > Which is why you have aerospace engineers designing the thing. > > > Larger means more surface > > area for your cyro tanks - and therefore thermal expansion/ > > contraction and thus more insulation and therefore more > > weight and so on and so forth. > > Actually, bigger tanks means less tank surface area to tank volume, which > means it's actually easier to deal with these sorts of issues. It seems > as though you're not understanding the scaling laws inherent in aerospace > design. > > > You really want your rocket to be as small as possible. > > Not necessarily. Some things get easier as you make the vehicle bigger, > like tank insulation and tps. A reentry vehicle that's mostly empty tankage > makes for easier tps since it will tend to decellerate more in the thin > upper atmosphere than a vehicle that's all dense payload and heavy engines, > like the shuttle. > > > Thus, > > you want high efficiency engines. > > You want that anyway. You can buy very efficient LOX/kerosene engines > today. Look at the Russian engines on Atlas V. Very good ISP (for > kerosene) with nice, dense kerosene fuel, making for much smaller tanks than > LH2 engines. > > > Materials and heat dissipation > > limit your chamber pressures. You can go for bigger chambers > > but now you've got to use bigger fuel pumps. > > Or you go for several engines. Look at the RD-170. It's one set of > turbopumps with four chambers. It puts out about 1,700,000 lbs of thrust at > sea level, which is a tad more than the venerable F-1 engine. However, the > RD-170 has a sea level ISP of 309 seconds while the F-1's sea level ISP is > only 265 seconds. > > With a cluster of five RD-170 engines, you've got 8,500,000 lbs of thrust to > play with. I think that would be plenty big while giving you the ability to > design for single engine out capability. ;-) > > >>Tell that to the guys flying B-52's. They're definately not quite the > >>same > >>vehicles as when they were built. One of these days, the funding for > >>upgrading the engines to turbofans will come through and they'll even > >> look > >>different on the outside. ;-) > > > > Yea, the '52 has certainly evolved - but then aircraft ARE > > easier to modify. It's also easier to test each modification, > > you'll only kill a few soldiers if it doesn't work ... > > It's easier to test modifications becuase it's reusable and you, hopefully, > get the test vehicle back after the flight! Intact recovery of a reusable > means you can inspect the thing after it flies and see how your > modifications performed. The flight may be successful, but you can inspect > it and easily find out how close to failure it actually came. This is much > harder to do with an expendable whose stages are typically destroyed during > flight and end up in pieces at the bottom of the ocean (lower stages) or end > up burning up completely in the atmosphere (upper stages) when they reenter > after doing their job. > > >>For that matter, look at the shuttle. There have been numerous upgrades > >>over the years along with even more numerous proposed upgrades that were > >>never funded. You certainly can refit existing airframes with newer > >>technologies and keep flying them. > > > > You can refit - but WITHIN LIMITS. They're not going to alter > > the shuttles external profile or major structural components. > > There's only so much room for certain kinds of components. The > > overall weight and balance can't change much. They're not going > > to completely re-wire it. > > > > Anyhow, I don't have much against reusable mission vehicles. > > Not much anyway. I'm more concerned with the boosters. Even > > thus, for many kinds of missions, a more conventional "capsule" > > would serve ... and you can throw it away later. You can make > > several kinds of capsules, each optimized for a specific kind > > of job. I think this would actually be cheaper and better than > > trying to build a does-it-all machine. > > Not necessarily. Using expendable launch vehicles means you're constrained > on how big you can make your capsules. This typically leads to capsule > designs that are very dense, making for hotter reentries and much more > challenging tps designs. > > > > > >>> The easiest 'disposable' route for spacecraft is to make > >>> maximum use of SRBs. Alone, or combined with LFRs so a > >>> range of thrust adjustment is possible, they're really > >>> a good way to add oomph without adding much cost. Not > >>> much more than a tube packed with 'powder'. > >> > >>Only if you like paying for entirely new vehicles after each and every > >>flight and will accept the cost and safety issues which arise from flying > >>expendables. > > > > The safety issues are managable. > > Shure, if you like to pay the cost of certifying and inspecting each and > every part before each and every flight. Sanely designed reusables are made > up of components that last far longer than one flight, so your inspection > requirements are far less per flight. This directly leads to lower per > flight launch costs. > > > The single one the shuttle > > program has failed to deal with is an incident where you > > may have to detach the SRBs early on, while they're still > > burning full power. This isn't too difficult to cope with, > > it's just that the current framework isn't designed to > > do the job. > > Actually it is difficult to deal with. The STS design originally > incorporated thrust termination for the SRB's, but it was dropped when it > became clear that the thrust transients involved in thrust termination would > tear the orbiter apart. This is one reason I dislike large solids. it's > very hard to turn them off in a non-violent way. > > > As for cost, SRBs do NOT have to be extremely expensive. > > You KNOW we're getting ripped-off by Thiokol - but they've > > managed to secure a position as sole shuttle SRB manufacturer > > ( I wonder how they managed that ?). New launch systems open > > the door to new bidders ... and, in theory, prices could be > > negotiated down considerably. > > They managed that because the flight rate is so low you can't justify having > more than one supplier for things like SRB's, ET's, or engines. Low flight > rate is a huge problem to launch vehicle economics. > > > Oh, and remember what I said about the evils of "bigness" ? > > That applies to SRBs too. The shuttles SRBs are difficult > > to make because they're so large. The propellant is cast > > in large 'pills' that really want to crack as they cure. > > The tube assembly had to be multi-jointed ... and we know > > what THAT caused. More, slimmer, SRBs may be the ticket. > > > > But, if you can come up with a really bare-bones liquid > > booster that doesn't leak fuel all over the place, doesn't > > cost a bleedin' fortune and can REALLY be reused five+ > > times then by all means sell it to NASA. > > > > Of course there's always the Rutan solution - nitrous > > oxide and ground-up tire rubber :-) > > Works just fine for the mission requirements. That's one of the signs of > good economics and engineering. Use the cheapest engine that meets > requirements. > > >>Intact abort is a good thing. It helps solve a lot of nagging problems > >>with > >>expendables independent of the whole launch cost thing. > > > > As I said, TOTALLY intact abort is almost certainly a pipe dream. > > Damn the boosters - SAVE THE PAYLOAD ! Satellites (and people) > > are EXPENSIVE. > > Funny, the shuttle design seems to include several intact abort modes that > save the crew and the payload. There are, unfortunately, a few other > abort modes that end with the crew bailing out, so the orbiter and payload > would be toast if you can't make it back to a runway. > > People aren't that expensive compared to a billion dollar payload. This is > true in many industries besides space travel. Take construction as an > example. On a challenging billion dollar construction project, it's likely > you're going to kill some number of workers due to accidents, so you buy > insurance. The insurance companies know very well how much a person's life > is worth, since they're the ones who typically pay out on such claims and > they're not in the business of losing money. > > Part of the reason we've got billion dollar payloads is that launch costs > are so high. That drives you towards bigger payloads that absolutely have > to work right the first time. Smaller, cheaper launches would drive > payloads the other way. And by cheaper, I mean at least an order of > magnitude cheaper. Small changes in launch costs won't change payload > design much. > > Jeff > -- > "They that can give up essential liberty to obtain a > little temporary safety deserve neither liberty nor > safety" > - B. Franklin, Bartlett's Familiar Quotations (1919) If I remember correctly DC-X never went into orbit. Was only capable of flying inside the athmosphere, thus was never subject to the stresses of entry, to name an example. Cheers, Einar Quote
Guest Rand Simberg Posted July 22, 2007 Posted July 22, 2007 On Sun, 22 Jul 2007 14:00:22 -0700, in a place far, far away, Einar <einarbb@gmail.com> made the phosphor on my monitor glow in such a way as to indicate that: <long snip> >You do make good arguments to someone who has no expertiece in this >particular field. But not so goo to those who do. > It certainly sounds plausable that modular >construction will reduce costs. Most certainly a single use booster is >cheaper than a multiuse one. No one has proposed a "multi-use booster." This is a straw man. And if you want people to read your posts, stop burying them at the bottom of a huge repost to which you add little value. If you have a response to a particular part of a post, respond to it there, and then go on to the next section, and respond to the next. If it's something you have no response or comment on, snip it. This is basic netiquette. Quote
Guest Einar Posted July 22, 2007 Posted July 22, 2007 Blackwater wrote: > Liquid-fueled boosters are vastly more complex machines > than SRBs. However, with good, sane, design they're not > necessarily less reliable. They have a few great advantages, > throttleability plus the ability to shut them down entirely > in case of emergency. IF we went with a "Russian" approach > and used clusters of rather small engines, they'd be just > fine for almost every purpose. If I remember correctly the Russians got into a plumbing problem with theyr N1 rocket. It had such a share number of engines, all liquied fueled it had become a plumbing nightmare. Cheers, Einar Quote
Guest Rand Simberg Posted July 22, 2007 Posted July 22, 2007 On Sun, 22 Jul 2007 14:07:52 -0700, in a place far, far away, Einar <einarbb@gmail.com> made the phosphor on my monitor glow in such a way as to indicate that: >If I remember correctly DC-X never went into orbit. Was only capable >of flying inside the athmosphere, thus was never subject to the >stresses of entry, to name an example. And once again, you quote hundreds of lines to respond with two sentences. Quote
Guest Blackwater Posted July 23, 2007 Posted July 23, 2007 On Sun, 22 Jul 2007 21:33:26 GMT, simberg.interglobal@org.trash (Rand Simberg) wrote: >On Sun, 22 Jul 2007 14:07:52 -0700, in a place far, far away, Einar ><einarbb@gmail.com> made the phosphor on my monitor glow in such a way >as to indicate that: > > >>If I remember correctly DC-X never went into orbit. Was only capable >>of flying inside the athmosphere, thus was never subject to the >>stresses of entry, to name an example. > >And once again, you quote hundreds of lines to respond with two >sentences. There's something to be said for brevity :-) And he's right - the DC-X was never fully tested. It remains a theoretical solution. Given DC politics and porkbarrel economics, don't expect further R&D from the US government. Now a private interest could indeed build on the idea. Don't discount the Chinese building their own either, once they've got a bit more experience in space. Such developments could eventually force NASA to build its own, if enough taxpayers complained about more wasteful systems and had a golden example of a LESS wasteful system to throw in the politicians faces. Quote
Guest Blackwater Posted July 23, 2007 Posted July 23, 2007 On Sun, 22 Jul 2007 20:33:14 GMT, Fred J. McCall <fmccall@earthlink.net> wrote: >bw@barrk.net (Blackwater) wrote: > >:On Sun, 22 Jul 2007 16:53:50 GMT, simberg.interglobal@org.trash (Rand >:Simberg) wrote: >: >:>On Thu, 19 Jul 2007 10:49:29 GMT, in a place far, far away, >:>bw@barrk.net (Blackwater) made the phosphor on my monitor glow in such >:>a way as to indicate that: >:> >:> >:>>>>>> Show me how to build a reusuable vehicle that ISN'T >:>>>>>> burdened-down by it's own complexity and requirements >:>>>>>> for reusability and I'll consider modifying my assessment. >:>>>>> >:>>>>>There is nothing wrong with complexity. A modern airliner is quite >:>>>>>complex. The primary difference between an air transport and a space >:>>>>>transport is the much higher fllight rate of the former. >:>>>> >:>>>> Um ... it's a little more involved than that. >:>>>> >:>>>> Think about it for a while. >:>>> >:>>>Believe me, I've thought about it a great deal. As an aerospace >:>>>professional, I've even been paid to think about it, and published >:>>>papers on it. Have you? >:>> >:>> >:>> Clearly I should be ... >:> >:><laughing> >:> >:>And yet you are not. You might want to consider why. >: >: >: Poor poltical connections, of course. >: >: Now if I was "Skull & Bones" ..... :-) >: > >I'd put it down to your 'poor neural connections', myself... Gee ... straight to the personal insults. You must be a 'liberal' :-) >:>> Paid to write sci-fi plots eh ? >:> >:>No. >: >: Pity. A lot of money in those ... >: > >Don't know much about writing, either, I see... The writers get scale ... the publishers or the ones who turn it into screenplays, THEY get the big bucks. Gotta have an eye for what's "good" of course ... >:>> Multiusable do-everything launch & mission vehicles >:>> are guarenteed to be too complex, too bulky and too >:>> expensive. >:> >:>Who said anything about "do-everything launch & mission vehicles"? >: >: >: That was what they tried to make the shuttle. >: >: And failed. >: > >Yep. And WHY did they fail? Because they accepted excessively high >operating costs to keep the development costs down. And if they'd proposed those sky-high development costs there would have BEEN no US "space program" to speak of. Given a choice of paying a big wad-o-cash up-front, even though the result will be a cash savings - OR - making installment payments forever and ever, most people choose the installment payments. Call it a human psychological quirk, but it's true. We just HATE to part with a big wad-o-cash. >:>Work on your reading comprehension. And once again, you're stuck on >:>the Shuttle, which is barely relevant to the discussion. >:> >:>> They are NOT "jetliners with rockets" by >:>> ANY stretch of the imagination. >:> >:>Who said they are? Work on your reading comprehension. >:> >: >: Sorry, but you DID imply that in terms of complexity >: shuttles and their launch system aren't much different >: than commercial airliners ... >: > >Where did he do that? Read backwards ... you'll find it. The sub-topic was 'complexity -vs- reliability' and the assertion was made that jetliners are very complex, yet reliable and built (relatively) cheaply, so spacecraft should enjoy the same. That's part of the problem of this thread however ... way too many subtopics glommed into each letter. Rapidly becomes very difficult to determine who said what, to whom, and what the context happened to be. >:>> Given the current >:>> technology (and political system) if you want economy >:>> and reliablity you go with standardized, modular, >:>> one-time-use components, heavy on the SRBs. NASA >:>> seems to agree and has put its money down for >:>> just that. >:> >:>Yes, and it's wasting the taxpayers' money once again. >:> >: >: Um ... yes - BUT the taxpayers wouldn't have gone for the >: MUCH higher up-front costs of a highly-resusable all-liquid >: fueled system. In short, they decided to HAVE a space program. >: Assuming the program returns things of value, then it's not >: "wasting the taxpayers money". >: >: So, your way = no program ... money spent bombing Afghanistan. >: >: My way = space program ... but with somewhat high monthly payments. >: >: Choose. >: > >If those are the only two choices, I choose the first one rather than >another program that just eats up money and shows how it CAN'T be >done... So you'd rather perpetuate a useless money-wasting war instead ? Ridiculous. >You want to repeat the same mistake that was made with the Shuttle. I think we NEED to repeat the COMPROMISE that allowed the shuttle to fly at all. >Many of the rest of us have learned that when it hurts you should stop >doing it. Old folks know better ... quit walking because your feet hurt and soon you'll never be able to walk again. Create a 'gap' in our manned space program now and it could be decades before anyone can get it going again, if ever. The "saved" money will NOT be "saved" - it will be wasted on sme porkbarrel idiocy instead. To sum it up "momentum" must be maintained. >Of course, your little exercise in the fallacy of the excluded middle >is irrelevant, since those are NOT the only two choices. In this case the middle IS excluded by default. There's no "halfway" manned space program - and if anyone tried such a thing, such a low-volume approach, it would be vastly more expensive than the STS or anything else we've discussed. Quote
Guest Fred J. McCall Posted July 23, 2007 Posted July 23, 2007 bw@barrk.net (Blackwater) wrote: :On Sun, 22 Jul 2007 20:33:14 GMT, Fred J. McCall :<fmccall@earthlink.net> wrote: : :>bw@barrk.net (Blackwater) wrote: :> :>:On Sun, 22 Jul 2007 16:53:50 GMT, simberg.interglobal@org.trash (Rand :>:Simberg) wrote: :>: :>:>On Thu, 19 Jul 2007 10:49:29 GMT, in a place far, far away, :>:>bw@barrk.net (Blackwater) made the phosphor on my monitor glow in such :>:>a way as to indicate that: :>:> :>:> :>:>>>>>> Show me how to build a reusuable vehicle that ISN'T :>:>>>>>> burdened-down by it's own complexity and requirements :>:>>>>>> for reusability and I'll consider modifying my assessment. :>:>>>>> :>:>>>>>There is nothing wrong with complexity. A modern airliner is quite :>:>>>>>complex. The primary difference between an air transport and a space :>:>>>>>transport is the much higher fllight rate of the former. :>:>>>> :>:>>>> Um ... it's a little more involved than that. :>:>>>> :>:>>>> Think about it for a while. :>:>>> :>:>>>Believe me, I've thought about it a great deal. As an aerospace :>:>>>professional, I've even been paid to think about it, and published :>:>>>papers on it. Have you? :>:>> :>:>> :>:>> Clearly I should be ... :>:> :>:><laughing> :>:> :>:>And yet you are not. You might want to consider why. :>: :>: :>: Poor poltical connections, of course. :>: :>: Now if I was "Skull & Bones" ..... :-) :>: :> :>I'd put it down to your 'poor neural connections', myself... :> : : Gee ... straight to the personal insults. You must : be a 'liberal' :-) : Care to guess again? : :>:>> Paid to write sci-fi plots eh ? :>:> :>:>No. :>: :>: Pity. A lot of money in those ... :>: :> :>Don't know much about writing, either, I see... :> : : The writers get scale ... the publishers or : the ones who turn it into screenplays, THEY : get the big bucks. Gotta have an eye for : what's "good" of course ... : So the "paid to write sci-fi" subthread was merely silly nattering. Even you knew better. :>:>> Multiusable do-everything launch & mission vehicles :>:>> are guarenteed to be too complex, too bulky and too :>:>> expensive. :>:> :>:>Who said anything about "do-everything launch & mission vehicles"? :>: :>: :>: That was what they tried to make the shuttle. :>: :>: And failed. :>: :> :>Yep. And WHY did they fail? Because they accepted excessively high :>operating costs to keep the development costs down. : : And if they'd proposed those sky-high development costs there : would have BEEN no US "space program" to speak of. : And that would have been worse how, again? : : Given a choice of paying a big wad-o-cash up-front, even though : the result will be a cash savings - OR - making installment : payments forever and ever, most people choose the installment : payments. Call it a human psychological quirk, but it's true. : We just HATE to part with a big wad-o-cash. : The problem is that your (and the Shuttle's) approach was neither of these. The "big wad-o-cash up-front" still had to be paid. It wasn't an installment purchase. The trade-off was for HIGHER OPERATING COSTS. Now look at what was promised for costs to orbit for the Shuttle and tell me that wasn't an outright lie. :>:>Work on your reading comprehension. And once again, you're stuck on :>:>the Shuttle, which is barely relevant to the discussion. :>:> :>:>> They are NOT "jetliners with rockets" by :>:>> ANY stretch of the imagination. :>:> :>:>Who said they are? Work on your reading comprehension. :>:> :>: :>: Sorry, but you DID imply that in terms of complexity :>: shuttles and their launch system aren't much different :>: than commercial airliners ... :>: :> :>Where did he do that? : : Read backwards ... you'll find it. The sub-topic was 'complexity : -vs- reliability' and the assertion was made that jetliners are : very complex, yet reliable and built (relatively) cheaply, so : spacecraft should enjoy the same. : He said no such thing. He didn't even mention the Shuttle. : : That's part of the problem of this thread however ... way too : many subtopics glommed into each letter. Rapidly becomes very : difficult to determine who said what, to whom, and what the : context happened to be. : Part of the problem appears to be someone reading things in that aren't there. :>:>> Given the current :>:>> technology (and political system) if you want economy :>:>> and reliablity you go with standardized, modular, :>:>> one-time-use components, heavy on the SRBs. NASA :>:>> seems to agree and has put its money down for :>:>> just that. :>:> :>:>Yes, and it's wasting the taxpayers' money once again. :>:> :>: :>: Um ... yes - BUT the taxpayers wouldn't have gone for the :>: MUCH higher up-front costs of a highly-resusable all-liquid :>: fueled system. In short, they decided to HAVE a space program. :>: Assuming the program returns things of value, then it's not :>: "wasting the taxpayers money". :>: :>: So, your way = no program ... money spent bombing Afghanistan. :>: :>: My way = space program ... but with somewhat high monthly payments. :>: :>: Choose. :>: :> :>If those are the only two choices, I choose the first one rather than :>another program that just eats up money and shows how it CAN'T be :>done... : : So you'd rather perpetuate a useless money-wasting war : instead ? Ridiculous. : The two aren't connected. This is merely specious 'logic' on your part. : :>You want to repeat the same mistake that was made with the Shuttle. : : I think we NEED to repeat the COMPROMISE that allowed the : shuttle to fly at all. : Why? So we can spend another generation going nowhere and losing capability? :>Many of the rest of us have learned that when it hurts you should stop :>doing it. : : Old folks know better ... quit walking because your feet hurt : and soon you'll never be able to walk again. Create a 'gap' : in our manned space program now and it could be decades before : anyone can get it going again, if ever. The "saved" money will : NOT be "saved" - it will be wasted on sme porkbarrel idiocy : instead. : : To sum it up "momentum" must be maintained. : But "momentum" toward what? All I see is the inertia of NASA 'workfare'. :>Of course, your little exercise in the fallacy of the excluded middle :>is irrelevant, since those are NOT the only two choices. : : In this case the middle IS excluded by default. There's no : "halfway" manned space program - and if anyone tried such : a thing, such a low-volume approach, it would be vastly more : expensive than the STS or anything else we've discussed. What you are suggesting IS a "halfway" manned space program. We've done that for decades and now couldn't get back to the Moon if we wanted to without taking MORE time and spending MORE money than we spend on the original trip. This is NOT progress... -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn Quote
Guest Blackwater Posted July 24, 2007 Posted July 24, 2007 On Mon, 23 Jul 2007 15:26:59 GMT, Fred J. McCall <fmccall@earthlink.net> wrote: >bw@barrk.net (Blackwater) wrote: > >:On Sun, 22 Jul 2007 20:33:14 GMT, Fred J. McCall >:<fmccall@earthlink.net> wrote: >: >:>bw@barrk.net (Blackwater) wrote: >:> >:>:On Sun, 22 Jul 2007 16:53:50 GMT, simberg.interglobal@org.trash (Rand >:>:Simberg) wrote: >:>: >:>:>On Thu, 19 Jul 2007 10:49:29 GMT, in a place far, far away, >:>:>bw@barrk.net (Blackwater) made the phosphor on my monitor glow in such >:>:>a way as to indicate that: >:>:> >:>:> >:>:>>>>>> Show me how to build a reusuable vehicle that ISN'T >:>:>>>>>> burdened-down by it's own complexity and requirements >:>:>>>>>> for reusability and I'll consider modifying my assessment. >:>:>>>>> >:>:>>>>>There is nothing wrong with complexity. A modern airliner is quite >:>:>>>>>complex. The primary difference between an air transport and a space >:>:>>>>>transport is the much higher fllight rate of the former. >:>:>>>> >:>:>>>> Um ... it's a little more involved than that. >:>:>>>> >:>:>>>> Think about it for a while. >:>:>>> >:>:>>>Believe me, I've thought about it a great deal. As an aerospace >:>:>>>professional, I've even been paid to think about it, and published >:>:>>>papers on it. Have you? >:>:>> >:>:>> >:>:>> Clearly I should be ... >:>:> >:>:><laughing> >:>:> >:>:>And yet you are not. You might want to consider why. >:>: >:>: >:>: Poor poltical connections, of course. >:>: >:>: Now if I was "Skull & Bones" ..... :-) >:>: >:> >:>I'd put it down to your 'poor neural connections', myself... >:> >: >: Gee ... straight to the personal insults. You must >: be a 'liberal' :-) >: > >Care to guess again? > >: >:>:>> Paid to write sci-fi plots eh ? >:>:> >:>:>No. >:>: >:>: Pity. A lot of money in those ... >:>: >:> >:>Don't know much about writing, either, I see... >:> >: >: The writers get scale ... the publishers or >: the ones who turn it into screenplays, THEY >: get the big bucks. Gotta have an eye for >: what's "good" of course ... >: > >So the "paid to write sci-fi" subthread was merely silly nattering. >Even you knew better. Just messin' with ya .... If you want to make big bucks, you have to write books about boy-wizards :-) >:>:>> Multiusable do-everything launch & mission vehicles >:>:>> are guarenteed to be too complex, too bulky and too >:>:>> expensive. >:>:> >:>:>Who said anything about "do-everything launch & mission vehicles"? >:>: >:>: >:>: That was what they tried to make the shuttle. >:>: >:>: And failed. >:>: >:> >:>Yep. And WHY did they fail? Because they accepted excessively high >:>operating costs to keep the development costs down. >: >: And if they'd proposed those sky-high development costs there >: would have BEEN no US "space program" to speak of. >: > >And that would have been worse how, again? Do I detect an anti-space bias ??? Admittedly, 'space' to date hasn't been as useful as promised - but then Orvill and Wilburs toy motor-kite didn't have many uses right away either. Still, you've got to start SOMEWHERE and that's what we've been doing. "W"'s little distraction, the new moon & Mars programs, I really don't see the POINT. What they're out to accomplish isn't all that more than what we've done before. A few extra people for a few extra days on the moon - whup-de-doo. Anything they could do, robots could do better. Mars - is unreachable at present. It's not the rockets, it's the damned radiation. Until they can shield the crews adequately on such a long, exposed, journey we just can't send people to mars. I've advocated saving the money on the moon program and instead putting it into robots. Not JUST for drilling around looking for water and minerals but also for construction purposes. Build a good moon base, one intended as the starter for a permanent colony, entirely with robots. Telepresence and a little smarts to begin with, more towards fully autonomous AI/swarm-AI later on as that technology develops. Use as many indigenous materials for construction as possible. MUCH cheaper (and safer) than sending humans to do the job. Finally, when it's fininshed ... Program "electric ants" as swarmbots and let them build a giant "anthill". They don't have to "know' what they are doing, the rules of interaction will get the job done. >: Given a choice of paying a big wad-o-cash up-front, even though >: the result will be a cash savings - OR - making installment >: payments forever and ever, most people choose the installment >: payments. Call it a human psychological quirk, but it's true. >: We just HATE to part with a big wad-o-cash. >: > >The problem is that your (and the Shuttle's) approach was neither of >these. The "big wad-o-cash up-front" still had to be paid. It wasn't >an installment purchase. The trade-off was for HIGHER OPERATING >COSTS. It WAS a govt project after all ... I think a lot of the real up-front costs were successfully hidden. The public got a glitz-and-glitter treatment of the whole endeavour, with the re-usability aspect hyped to the max. For years, we got propaganda, the idea that everything was going well, cheaply, when the ACTUAL amount spent and the ACTUAL reusability aspects didn't measure up. The public likes to believe what it's told - saves mental effort. Even now, most people don't think the shuttle program is too expensive to bother with - and nobody reminds them of how cheap it was SUPPOSED to be. Everyone is happy since they're ignorant of how happy they COULD have been. Even thus, without the expedient of the SRBs, I wonder whether even the politicians could have pulled-off the snow job. >Now look at what was promised for costs to orbit for the Shuttle and >tell me that wasn't an outright lie. > >:>:>Work on your reading comprehension. And once again, you're stuck on >:>:>the Shuttle, which is barely relevant to the discussion. >:>:> >:>:>> They are NOT "jetliners with rockets" by >:>:>> ANY stretch of the imagination. >:>:> >:>:>Who said they are? Work on your reading comprehension. >:>:> >:>: >:>: Sorry, but you DID imply that in terms of complexity >:>: shuttles and their launch system aren't much different >:>: than commercial airliners ... >:>: >:> >:>Where did he do that? >: >: Read backwards ... you'll find it. The sub-topic was 'complexity >: -vs- reliability' and the assertion was made that jetliners are >: very complex, yet reliable and built (relatively) cheaply, so >: spacecraft should enjoy the same. >: > >He said no such thing. He didn't even mention the Shuttle. Are we talking about the same person ? Same sub-thread ? >: That's part of the problem of this thread however ... way too >: many subtopics glommed into each letter. Rapidly becomes very >: difficult to determine who said what, to whom, and what the >: context happened to be. >: > >Part of the problem appears to be someone reading things in that >aren't there. Seemed "there" to me ... >:>:>> Given the current >:>:>> technology (and political system) if you want economy >:>:>> and reliablity you go with standardized, modular, >:>:>> one-time-use components, heavy on the SRBs. NASA >:>:>> seems to agree and has put its money down for >:>:>> just that. >:>:> >:>:>Yes, and it's wasting the taxpayers' money once again. >:>:> >:>: >:>: Um ... yes - BUT the taxpayers wouldn't have gone for the >:>: MUCH higher up-front costs of a highly-resusable all-liquid >:>: fueled system. In short, they decided to HAVE a space program. >:>: Assuming the program returns things of value, then it's not >:>: "wasting the taxpayers money". >:>: >:>: So, your way = no program ... money spent bombing Afghanistan. >:>: >:>: My way = space program ... but with somewhat high monthly payments. >:>: >:>: Choose. >:>: >:> >:>If those are the only two choices, I choose the first one rather than >:>another program that just eats up money and shows how it CAN'T be >:>done... >: >: So you'd rather perpetuate a useless money-wasting war >: instead ? Ridiculous. >: > >The two aren't connected. This is merely specious 'logic' on your >part. But they ARE connected - through the federal budget. Money not spent one place will be spent in another place (refunds ? real tax cuts ? forget it). >:>You want to repeat the same mistake that was made with the Shuttle. >: >: I think we NEED to repeat the COMPROMISE that allowed the >: shuttle to fly at all. >: > >Why? So we can spend another generation going nowhere and losing >capability? We won't be "losing capability" ... just not moving ahead very far with it. The REAL next step for humans in space should be a permanent, expanding, self-sustaining, ultimately self-financing moon colony. Until then, all robots. However issues of 'national pride' intervene, as well as concerns about 'reds' getting ahead. This guarentees that we WILL have some kind of manned space program, even IF it's expensive and gets nowhere. >:>Many of the rest of us have learned that when it hurts you should stop >:>doing it. >: >: Old folks know better ... quit walking because your feet hurt >: and soon you'll never be able to walk again. Create a 'gap' >: in our manned space program now and it could be decades before >: anyone can get it going again, if ever. The "saved" money will >: NOT be "saved" - it will be wasted on sme porkbarrel idiocy >: instead. >: >: To sum it up "momentum" must be maintained. >: > >But "momentum" toward what? All I see is the inertia of NASA >'workfare'. Reality -vs- image. The taxpayers think we're getting somewhere, or at least like a good show. Most of the shuttle missions actually accomplished nothing of interest whatsoever, they were all "been there, done that" or could have been done via automation for a tenth the price. But that's not how the program is perceived . >:>Of course, your little exercise in the fallacy of the excluded middle >:>is irrelevant, since those are NOT the only two choices. >: >: In this case the middle IS excluded by default. There's no >: "halfway" manned space program - and if anyone tried such >: a thing, such a low-volume approach, it would be vastly more >: expensive than the STS or anything else we've discussed. > >What you are suggesting IS a "halfway" manned space program. > >We've done that for decades and now couldn't get back to the Moon if >we wanted to without taking MORE time and spending MORE money than we >spend on the original trip. > >This is NOT progress... I agree. "Regress prevention" instead. Quote
Guest scolbourne_2000@yahoo.co.uk Posted July 26, 2007 Posted July 26, 2007 Here is a cheap easy way to get to space. I am surprised you lot do not think to use it instead of rockets. It would be obvious to even a five year old. Use a swing. Stick a swing in orbit so that the "seat" comes in to Earth in the opposite direction to the orbit, (and rotates over the top to avoid air drag). Ground speed can be arranged to be zero when payload or astronauts board. The swing will then transport you into orbit or further for very little energy. Any energy losses can be made up by working electrically against the Earths magentic fields. A more sensible version of this would keep the whole system in orbit not coming too far down into the Earths atmosphere. sub orbital rockets (such as Virgin will soon possess) will then be suitable for the transfer . Quote
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