#41
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The 100/10/1 Rule.
Danny Deger wrote:
"Reunite Gondwanaland (Mary Shafer)" wrote in message ... On Sun, 04 Mar 2007 20:46:23 -0600, kT wrote: However, one can argue that the expendable SSTO approach puts almost an order of magnitude more mass into orbit, which is what I am suggesting. Has anyone ever put anything into orbit with a single stage? I know we've managed SSTS, Single Stage To Space, but I don't think we've managed SSTO. I don't think so. SSTO requires engines for efficent than we have and requires fuel tanks lighter than we have. Both of these technologies need to be developed to make a SSTO space craft. NASA tried to develop these technologies a few year ago and failed in both. I don't know if there is even a concept out there to make SSTO possible. Er ... no, it should be doable in aluminum and SSMEs. The SSMEs at propulsive efficiencies in the low to mid 90s is as good as it's gonna get anytime in the near future. We're years away from full flow staged combustion. However, there are clear roadmaps to improvement, and thus SSTO presents no modern breakthroughs, it's just straightforward R&D and engineering. The necessary structural efficiencies are clearly in the range of modern materials and modern structural design techniques. It's when you start adding all kinds of wings and landing gear that things get iffy, so I propose just starting out with the basics. I'm shooting for a 35,000 lb. vehicle. Anything more than that and I'll need GEM-60s, and then the whole thing falls apart rather quickly. What we really need, a real simple thing : an RL-60. -- Get A Free Orbiter Space Flight Simulator : http://orbit.medphys.ucl.ac.uk/orbit.html |
#42
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The 100/10/1 Rule.
Pat Flannery wrote:
The Atlas H 1/2 stage weighed 8,038 lb according to Encyclopedia Astronautica; payload to LEO is 8,000 pounds, so with a lightweight aerodynamic nosecone, who knows? Is it possible that with the booster engines attached all the way to orbit, the vehicle could fly a somewhat more efficient trajectory, therefore boosting the payload a bit? On the other hand, the booster engines might have to be shut down anyway in order to keep the acceleration from damaging the structure. |
#43
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The 100/10/1 Rule.
"Danny Deger" wrote in message ... "Reunite Gondwanaland (Mary Shafer)" wrote in message ... On Sun, 04 Mar 2007 20:46:23 -0600, kT wrote: However, one can argue that the expendable SSTO approach puts almost an order of magnitude more mass into orbit, which is what I am suggesting. Has anyone ever put anything into orbit with a single stage? I know we've managed SSTS, Single Stage To Space, but I don't think we've managed SSTO. I don't think so. True, SSTO has not been demonstrated. SSTO requires engines for efficent than we have and requires fuel tanks lighter than we have. False, especailly for an expendable SSTO. An expendable SSTO isn't all that hard to do, it's just that no one has tried. The "performance uber alles" philosophy of your typical aerospace engineer makes them *really* want to drop some of the heavy bits on the way up, even if it adds complexity and cost to the design because they always think that the performance gained is worth the added cost. As Henry has pointed out many times, a shuttle ET with about six SSME's on the bottom could put (roughly) the same payload in orbit as the shuttle. And that's with a generous weight allowance for thrust structure, plumbing, and etc. Both of these technologies need to be developed to make a SSTO space craft. NASA tried to develop these technologies a few year ago and failed in both. False. X-33 failed due to a combination of NASA picking the technically most difficult proposal (there were three competing proposals from different contractors) and due to lack of incentive on either side to actually make the vehicle fly. The "obvious" choice to me would have been the DC-X like proposal. Simpler aerodynamics, simpler structure, simpler engines, simpler flight control software, and etc. I'm sure Mary can tell you, from an aerodynamics point of view, how hard it is to design a winged, or lifting body, unpowered re-entry vehicle that's stable throughout hypersonic flight all the way down to subsonic flight and landing. As time went on, the Venture Star (X-33 follow-on) design went from a lifting body with stubby aerodynamic surfaces to a "lifting body" with aerodynamic surfaces that sure looked big enough to be called wings. That was very telling. I don't know if there is even a concept out there to make SSTO possible. Then you're not looking very hard, are you? If you look at astronautix.com, you'll likely find dozens of proposals dating back decades. 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) |
#44
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The 100/10/1 Rule.
Proponent wrote: Is it possible that with the booster engines attached all the way to orbit, the vehicle could fly a somewhat more efficient trajectory, therefore boosting the payload a bit? On the other hand, the booster engines might have to be shut down anyway in order to keep the acceleration from damaging the structure. I assume they carefully worked out to the second when the boosters became a net deficit to the ascent, and jettisoned them at that point. Although they each generated over twice as much thrust as the core engine, their Isp was inferior to it. 290 vs 316 in vacuum respectively: http://www.astronautix.com/engines/lr895.htm http://www.astronautix.com/engines/lr1055.htm Pat |
#45
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The 100/10/1 Rule.
Jeff Findley wrote: False, especailly for an expendable SSTO. An expendable SSTO isn't all that hard to do, it's just that no one has tried. The "performance uber alles" philosophy of your typical aerospace engineer makes them *really* want to drop some of the heavy bits on the way up, even if it adds complexity and cost to the design because they always think that the performance gained is worth the added cost. You can see the germ of Atlas in North Amercian Aviation's HATV design from 1946: http://history.nasa.gov/SP-4202/p1-10.jpg You can just see an engineer looking at that, and thinking: "Now , if we could jettison the eight small motors once a lot of the fuel was burnt..." Pat |
#46
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The 100/10/1 Rule.
"Danny Deger" wrote in message ... "Reunite Gondwanaland (Mary Shafer)" wrote in message ... On Sun, 04 Mar 2007 20:46:23 -0600, kT wrote: However, one can argue that the expendable SSTO approach puts almost an order of magnitude more mass into orbit, which is what I am suggesting. Has anyone ever put anything into orbit with a single stage? I know we've managed SSTS, Single Stage To Space, but I don't think we've managed SSTO. I don't think so. SSTO requires engines for efficent than we have and requires fuel tanks lighter than we have. Both of these technologies need to be developed to make a SSTO space craft. NASA tried to develop these technologies a few year ago and failed in both. I don't know if there is even a concept out there to make SSTO possible. I stand corrected on this. An expendable SSTO is very feasible. The X-33 had problems in large part because it also was attempting to do an atmospheric entry. The entry requirement added a lot of mass to the system. Danny Deger |
#47
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The 100/10/1 Rule.
On Thu, 8 Mar 2007 09:18:31 -0600, Danny Deger wrote
(in article ): I stand corrected on this. An expendable SSTO is very feasible. But doesn't really serve much purpose - staging is a very mature technology and allows huge improvements in upmass. -- You can run on for a long time, Sooner or later, God'll cut you down. ~Johnny Cash |
#48
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The 100/10/1 Rule.
Herb Schaltegger wrote:
On Thu, 8 Mar 2007 09:18:31 -0600, Danny Deger wrote (in article ): I stand corrected on this. An expendable SSTO is very feasible. But doesn't really serve much purpose - staging is a very mature technology and allows huge improvements in upmass. And we are all so grateful for the astronomical increase in costs associated with staging. All those engines, so little time. -- Get A Free Orbiter Space Flight Simulator : http://orbit.medphys.ucl.ac.uk/orbit.html |
#49
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The 100/10/1 Rule.
On Thu, 8 Mar 2007 09:40:58 -0600, kT wrote
(in article ): And we are all so grateful for the astronomical increase in costs associated with staging. All those engines, so little time. The "astronomical costs" of hardware are insignificant. The real expense is the payload, which benefits greatly from being allowed to be bigger than a grapefruit and mass more than 100 kilograms. -- You can run on for a long time, Sooner or later, God'll cut you down. ~Johnny Cash |
#50
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The 100/10/1 Rule.
Herb Schaltegger wrote:
On Thu, 8 Mar 2007 09:40:58 -0600, kT wrote (in article ): And we are all so grateful for the astronomical increase in costs associated with staging. All those engines, so little time. The "astronomical costs" of hardware are insignificant. No wonder space has been so thoroughly colonized already then. Good job people, kudos all around. -- Get A Free Orbiter Space Flight Simulator : http://orbit.medphys.ucl.ac.uk/orbit.html |
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