As for ATK's power - you have to realise that Boeing and Lockheed have similar sized lobby groups too.
Someone, earlier, introduced the fact that the SRB (compared to the liquid engines) will always light and won't shut down until it is supposed to. Is this still a factor?
Someone, earlier, introduced the fact that the SRB (compared to the liquid engines) will always light and won't shut down until it is supposed to.Is this still a factor?
Well, I think its bigger advantages are that it is storable and has high energy density. That is why it is useful for rapidly deployed ICBMs.
Quote from: guru on 07/24/2008 07:28 pmWell, I think its bigger advantages are that it is storable and has high energy density. That is why it is useful for rapidly deployed ICBMs.Storability is a plus, but it's important only for military, not for space LVs.
Energy density is not important
total dV is, which is related but different metric - if you have lighter gases in exhaust, your Isp is higher at the same energy. A kerolox booster of same dimensions and thrust outperforms a SRM.
I think flyback kerolox reusable boosters would be better than the solids. The flyback booster reusable as a single rocket could also launch the Orion capsule. Less vibration on the suttle stack would also be safer for the shuttle from foam debris. If you went with a kerolox shuttle engine with ground start, but throttled way down, you wouldn't have to insulate the tank, no foam problems.
Quote from: edkyle99 on 07/24/2008 02:01 amRD-180 would be more likely than RD-171 because it is already being imported by ULA, etc..Even though you say that Pratt and Whitney is abandoning their RD-AMROSS effort?
RD-180 would be more likely than RD-171 because it is already being imported by ULA, etc..
Running some numbers quickly, this *might* be able to fly the current ~22,500kg Lunar-capable Orion.T:W at liftoff carrying a full Ares-I Upper Stage is only 1.03 and first stage performance carrying that is truly awful. So, to get any sort of reasonable performance you're looking at the US needing to being shrunk quite a bit.Dropping it to around the optimum, which appears to be around 50,000kg capacity, the first stage still seems underpowered with a T:W 1.19. I can insert an Orion to 130x130nm, 29.0deg, but dynamic pressure (max-Q) is obscenely high, well above 1000psf. All my runs assumed the full 108% RS-68 and the full 294,000lb thrust J-2X....Ross.
The kerolox shuttle engine throttled way down would be throttled up to orbit when the boosters dropped off.
Running some numbers quickly, this *might* be able to fly the current ~22,500kg Lunar-capable Orion.T:W at liftoff carrying a full Ares-I Upper Stage is only 1.03 and first stage performance carrying that is truly awful. So, to get any sort of reasonable performance you're looking at the US needing to being shrunk quite a bit.Dropping it to around the optimum, which appears to be around 50,000kg capacity, the first stage still seems underpowered with a T:W 1.19. I can insert an Orion to 130x130nm, 29.0deg, but dynamic pressure (max-Q) is obscenely high, well above 1000psf. All my runs assumed the full 108% RS-68 and the full 294,000lb thrust J-2X.Ross.
Regarding big domestic RP engine available in early 00s: it's debatable whether Atlas V would have gone that route since RD-180 was so cheap.
These numbers could be increased significantly if a TAN were used on the RS-68.
QuoteEnergy density is not importantNot true. If the entire Saturn V only stored 1 Joule worth of chemical energy, then it's maximum velocity would be sqrt(2J / 3,000,000 kg) = .0008 m/s.
Quote from: clongton on 07/25/2008 11:09 amThese numbers could be increased significantly if a TAN were used on the RS-68.TAN?