Quote from: theinternetftw on 03/16/2018 06:31 am* Develop and build a Lunar Excursion Vehicle: the LEV. Cabin the size of the LM. 2 tons.* Have on the LEV a hydrolox stage with enough fuel to do TEI and then EOI back to LEO. All told, 6 km/s.* The above requires a mass ratio of 3.7, resulting in a 8 ton vehicle.* Put all that in a cargo module, to be landed by the previously developed cargo lander.Delta-V is Ascent+TEI+TCM+EOI+1% margin = (1890+1169+2+3185)*1.01 = 6308.5 m/s. RL-10C-2 ve = 4535.6 m/s. Mass ratio = exp(6308.5/4535.6) = 4.018. An 8 t vehicle would then have a dry mass of 1.99 t, including the cabin! Not going to work. Assuming a mc = 2000 kg cabin, one me = 301 kg engine, two crew at mh = 125 kg each and mr = 100 kg of samples, a stage dry mass model of ms = 0.46718*mp^{0.848}, I get ms = 1353 kg and mp = 12085 kg. Total mass is mc+2*mh+mr+me+ms+mp = 2000+2*125+100+301+1353+12085 = 16,089 kg, which is 4.1 t greater than the 12 t that can be landed!Attached is a little program that I used for working out the stage mass. You can also use it for other hydrolox stages! Just enter the delta-V, exhaust speed, cargo mass, engine mass and number of engines.
* Develop and build a Lunar Excursion Vehicle: the LEV. Cabin the size of the LM. 2 tons.* Have on the LEV a hydrolox stage with enough fuel to do TEI and then EOI back to LEO. All told, 6 km/s.* The above requires a mass ratio of 3.7, resulting in a 8 ton vehicle.* Put all that in a cargo module, to be landed by the previously developed cargo lander.
Quote from: Steven Pietrobon on 03/18/2018 06:54 amQuote from: theinternetftw on 03/16/2018 06:31 am* Develop and build a Lunar Excursion Vehicle: the LEV. Cabin the size of the LM. 2 tons.* Have on the LEV a hydrolox stage with enough fuel to do TEI and then EOI back to LEO. All told, 6 km/s.* The above requires a mass ratio of 3.7, resulting in a 8 ton vehicle.* Put all that in a cargo module, to be landed by the previously developed cargo lander.Delta-V is Ascent+TEI+TCM+EOI+1% margin = (1890+1169+2+3185)*1.01 = 6308.5 m/s. RL-10C-2 ve = 4535.6 m/s. Mass ratio = exp(6308.5/4535.6) = 4.018. An 8 t vehicle would then have a dry mass of 1.99 t, including the cabin! Not going to work. Assuming a mc = 2000 kg cabin, one me = 301 kg engine, two crew at mh = 125 kg each and mr = 100 kg of samples, a stage dry mass model of ms = 0.46718*mp^{0.848}, I get ms = 1353 kg and mp = 12085 kg. Total mass is mc+2*mh+mr+me+ms+mp = 2000+2*125+100+301+1353+12085 = 16,089 kg, which is 4.1 t greater than the 12 t that can be landed!Attached is a little program that I used for working out the stage mass. You can also use it for other hydrolox stages! Just enter the delta-V, exhaust speed, cargo mass, engine mass and number of engines.The 2 t mass figure is for the whole Apollo ascent stage, not just a crew cabin. So includes mass of engines and tanks you have counted separately. Probably saves at least half a ton, plus further reductions in propellant and stage mass. Also, the RL-10 could lift about 70 t on the moon, which is overkill, so could probably get away with much lighter engine.
Falcon Heavy definitively lowers the costs and increases the mass that can be sent per launch, and if anyone gets serious about this the ULA ACES hardware could be a good platform to use.I've always been fond of the ACES-derived horizontal landers - they seem like an elegant solution, as opposed to the "Apollo on steroids" Altair type solutions NASA was planning to pursue.
So the idea is to haul TEI and EOI propellant down to the lunar surface, leave behind an expendable lander, and then leave an expendable LEV in LEO because we're afraid of orbital refueling? How could it possibly make sense to pay such a high price for an EOI burn on the way back to LEO without a commitment to reuse the LEV?This is just Apollo Direct Ascent, except with the theory that hauling around EOI propellant (and doing an extra ".5" launch) is preferable to hauling around a heatshield. I'm not convinced it is.
To me a LEV that would go back and forth from the ISS should be something considered.
Quote from: ChrisWilson68 on 03/17/2018 06:24 pmPlus, on the one Falcon 9 in-flight failure, the LAS would have saved the crew.Would it? The LAS is essentially a rocket stage with components similar in function to what failed on the two Falcon 9 failures. It could fall apart just as easily as what it is attached to. Same manufacturer. In the two Falcon 9 failures, the stage that failed wasn't even active at the time.
Plus, on the one Falcon 9 in-flight failure, the LAS would have saved the crew.
BFR may be too big for the Dragon 2 life support system, unless 5-10 copies are used.
Last 20 missions would be STS-115(Sept. 2006) through STS-135 (July 2011). All were successful.
It seems like the crew section of the plan (FH with crew lander, plus F9 with crew) might be an issue. FH can deliver however many tons to the Moon (meaning stage 2 makes a TLI burn), but this architecture requires that FH make such a TLI burn for the crew lander, right? This means that the crew Dragon needs to rendezvous with the FH upper stage during whatever its max coast period is. Sounds like a logistical issue. One #waywardboat and there's a big problem.
Currently crew is only 39A.So short of some serious infrastructure changes, the launches would serially be at the same pad.
Of course it seems like the best way to pitch something like this would be to have the crew vehicle be CST-100 (includes more players).
Quote from: tater on 03/18/2018 02:07 pmIt seems like the crew section of the plan (FH with crew lander, plus F9 with crew) might be an issue. FH can deliver however many tons to the Moon (meaning stage 2 makes a TLI burn), but this architecture requires that FH make such a TLI burn for the crew lander, right? This means that the crew Dragon needs to rendezvous with the FH upper stage during whatever its max coast period is. Sounds like a logistical issue. One #waywardboat and there's a big problem.IIRC Dr. Zubrin suggested that the FH inserts the LEV into a GTO/GEO-like high orbit. Dragon will rendezvous with the LEV there. Dragon stays and the (now dV-wise small) TLI burn is done by the LEV.
That also likely makes timing even more critical I would assume, since the crew vehicle then needs to rendezvous with an eccentric orbit, and one that is specifically oriented for efficient lunar orbit injection. If you missed what is (necessarily?) an instantaneous launch window, when's the next one, next month, or in a few weeks?
Quote from: tater on 03/18/2018 02:52 pmCurrently crew is only 39A.So short of some serious infrastructure changes, the launches would serially be at the same pad.Not impossible, I suppose. And a 24-hour turnaround is better for inclination-matching, anyway. Though, does the 39A hangar have space for four cores at a time?QuoteOf course it seems like the best way to pitch something like this would be to have the crew vehicle be CST-100 (includes more players).This would be true if CST100 had ANY advantage over Dragon 2. It's way heavier. Does it have more onboard dV?
IIRC Dr. Zubrin suggested that the FH inserts the LEV into a GTO/GEO-like high orbit. Dragon will rendezvous with the LEV there. Dragon stays and the (now dV-wise small) TLI burn is done by the LEV.
This would be true if CST100 had ANY advantage over Dragon 2. It's way heavier. Does it have more onboard dV?
Delta-V is Ascent+TEI+TCM+EOI+1% margin = (1890+1169+2+3185)*1.01 = 6308.5 m/s. RL-10C-2 ve = 4535.6 m/s. Mass ratio = exp(6308.5/4535.6) = 4.018. An 8 t vehicle would then have a dry mass of 1.99 t, including the cabin! Not going to work. Assuming a mc = 2000 kg cabin, one me = 301 kg engine, two crew at mh = 125 kg each and mr = 100 kg of samples, a stage dry mass model of ms = 0.46718*mp^{0.848}, I get ms = 1353 kg and mp = 12085 kg. Total mass is mc+2*mh+mr+me+ms+mp = 2000+2*125+100+301+1353+12085 = 16,089 kg, which is 4.1 t greater than the 12 t that can be landed!
Quote from: FinalFrontier on 03/17/2018 10:11 pmIt is not a decent architecture. Why is this proposal a thing? Why isn't he proposing COTS/CRS/CCDEV for BEO? Something that would be far easier to sell to Congress (there is already discussion of using commercial launchers for pieces of the Lunar Platform thing)? Elephant in the room is being ignored once again, money being wasted on a giant NASA rocket and spacecraft that could be better served elsewhere. Good luck paying for lunar mission elements while simultaneously funding that nonsense. I am somewhat upset that Dr. Zubrin and others in similar positions don't want to talk about this issue. It is only going to get worse and more pronounced as time goes by and the commercial sector continues to mature. They don't want to talk about it to the point they are proposing whole new mission architectures and totally ignoring it.I think Zubrin is proposing this as a replacement for DSG. He didn't propose concepts like COTS probably because he wants to show something concrete for politicians to visualize (i.e. boots on the Moon in x years). Besides, the administration's FY19 budget request already has proposal for public private partnership on lunar lander, it's called Advanced Cislunar and Surface Capabilities (ACSC), but it doesn't have a lot of funding ($116.5M for FY19, increases to $320.3M in FY23). If the administration can be convinced to move DSG's funding into lander development, then there should be enough to do something like Zubrin suggested (it probably won't launch on FH though). All of these can be done without tackling the harder problem of cancelling SLS/Orion, at least I think that's his plan.
It is not a decent architecture. Why is this proposal a thing? Why isn't he proposing COTS/CRS/CCDEV for BEO? Something that would be far easier to sell to Congress (there is already discussion of using commercial launchers for pieces of the Lunar Platform thing)? Elephant in the room is being ignored once again, money being wasted on a giant NASA rocket and spacecraft that could be better served elsewhere. Good luck paying for lunar mission elements while simultaneously funding that nonsense. I am somewhat upset that Dr. Zubrin and others in similar positions don't want to talk about this issue. It is only going to get worse and more pronounced as time goes by and the commercial sector continues to mature. They don't want to talk about it to the point they are proposing whole new mission architectures and totally ignoring it.