#31
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The 100/10/1 Rule.
Pat Flannery wrote:
Henry Spencer wrote: Addendum: And there have been several rediscoveries of the fact that if you put six or seven SSMEs underneath an ET, even with generous allowances for things like thrust structure, it makes orbit with about the same payload as the shuttle. What about RS-68s? You would be hard pressed to get an RS-68 to go single stage. The T/W ratio is twice the SSME, and the Isp is lower. Plus it's a ... ahem ... hard starter. -- Get A Free Orbiter Space Flight Simulator : http://orbit.medphys.ucl.ac.uk/orbit.html |
#32
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The 100/10/1 Rule.
Pat Flannery wrote:
Charles Buckley wrote: I remember the thread Scott refers to. IIRC, there is an amateur group out in CA that is using that as its baseline since the supersonic milestone by amateurs has been met. Spaceflight is the next amateur milestone. The article actually had a picture of the rocket; it was pretty hilarious-looking. I noticed that cool geocities site you posted immediately went over bandwidth. How long do I have to wait for that to come back online? Did anybody think to download any images off of it? -- Get A Free Orbiter Space Flight Simulator : http://orbit.medphys.ucl.ac.uk/orbit.html |
#33
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The 100/10/1 Rule.
You would be hard pressed to get an RS-68 to go single stage.
The T/W ratio is twice the SSME, and the Isp is lower. Isn't the engine T/W somewhat irrelevant? You need a suitable mass fraction of the whole stage to get to orbit, and the engine mass surely is only a small fraction of the total dry weight. Jan |
#34
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The 100/10/1 Rule.
Jan Vorbrüggen wrote:
You would be hard pressed to get an RS-68 to go single stage. The T/W ratio is twice the SSME, and the Isp is lower. Isn't the engine T/W somewhat irrelevant? You need a suitable mass fraction of the whole stage to get to orbit, and the engine mass surely is only a small fraction of the total dry weight. You can easily simulate this in orbiter to first order approximation. I just haven't bothered to do it yet, because the way it stands right now, if I want to fly either the RS-68 or the RL-10, I can fly the Delta IV. In my SSME based test vehicle, engine weight is 20%. Everything that has mass is relevant to SSTO. -- Get A Free Orbiter Space Flight Simulator : http://orbit.medphys.ucl.ac.uk/orbit.html |
#35
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The 100/10/1 Rule.
kT wrote:
Jan Vorbrüggen wrote: You would be hard pressed to get an RS-68 to go single stage. The T/W ratio is twice the SSME, and the Isp is lower. Isn't the engine T/W somewhat irrelevant? You need a suitable mass fraction of the whole stage to get to orbit, and the engine mass surely is only a small fraction of the total dry weight. You can easily simulate this in orbiter to first order approximation. I just haven't bothered to do it yet, because the way it stands right now, if I want to fly either the RS-68 or the RL-10, I can fly the Delta IV. In my SSME based test vehicle, engine weight is 20%. Everything that has mass is relevant to SSTO. Actually I mispoke, the RAW mass of the RS-68 is twice the SSME. You're right T/W is somewhat less important here. I think it's in the 50 to 1 range. -- Get A Free Orbiter Space Flight Simulator : http://orbit.medphys.ucl.ac.uk/orbit.html |
#36
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The 100/10/1 Rule.
"Reunite Gondwanaland (Mary Shafer)" writes:
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. Would you count the 1958 SCORE (Signal Communications Orbit Relay Equipment), allowing that the Atlas B didn't shed a *whole* stage on its ascent? -- Joseph Nebus ------------------------------------------------------------------------------ Can we argue the definition of 'stage' until all comprehension is lost and only nitpicking remains? |
#37
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The 100/10/1 Rule.
In article ,
Joseph Nebus wrote: Has anyone ever put anything into orbit with a single stage? ... Would you count the 1958 SCORE (Signal Communications Orbit Relay Equipment), allowing that the Atlas B didn't shed a *whole* stage on its ascent? Alas, realistically, the classical Atlas -- which launched the orbital Mercury flights and several other things, in addition to SCORE -- has to be deemed a two-stage vehicle for this purpose. It didn't drop a whole stage, no, but it dropped most of the heavy parts of one. (And some parts of the "upper stage", too -- notably, the entire tank-pressurization system departed with the booster engines! The gas left in the mostly-empty tanks was sufficient to keep them pressurized thereafter, aided by hydrostatic head from high acceleration.) -- spsystems.net is temporarily off the air; | Henry Spencer mail to henry at zoo.utoronto.ca instead. | |
#38
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The 100/10/1 Rule.
In article ,
Pat Flannery wrote: Addendum: And there have been several rediscoveries of the fact that if you put six or seven SSMEs underneath an ET, even with generous allowances for things like thrust structure, it makes orbit with about the same payload as the shuttle. What about RS-68s? Haven't done the analysis, but my gut feeling is, not so good -- this is one place where the RS-68's lower performance really does hurt. -- spsystems.net is temporarily off the air; | Henry Spencer mail to henry at zoo.utoronto.ca instead. | |
#39
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The 100/10/1 Rule.
kT wrote: I noticed that cool geocities site you posted immediately went over bandwidth. How long do I have to wait for that to come back online? I'm not sure which one you are referring to, but I think it's a daily thing, isn't it? Or is it monthly? Rusty Barton's ICBM websites used to have that problem a lot, because they were so well done. Pat |
#40
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The 100/10/1 Rule.
"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. Danny Deger Mary "Haven't thought about this for years" -- Mary Shafer Retired aerospace research engineer We didn't just do weird stuff at Dryden, we wrote reports about it. or Visit my new blog at http://thedigitalknitter.blogspot.com/ |
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