Quote from: Lars-J on 02/22/2017 03:41 pmJ-2X didn't go so well, did it? Over budget/schedule, underperforming, and shelved.Please provide a reference showing that J-2X was over budget/schedule and underperforming. That was not my impression.
J-2X didn't go so well, did it? Over budget/schedule, underperforming, and shelved.
Playing around with Dragon2 and Falcon Heavy Capabilities some more, and looking at cargo or empty lander came up with the following:Dragon 2 with same 5570kg dry mass and 1815 kg prop:Fully expendable FH 54,400 kg to LEO (partial kerelox prop mass, delta II stage + Dragon 2)FH US partial burn to LLO 3.47 km/s dVDelta II US remainder 1600 kg burn to LLO 0.57 km/s dV (4.04 dV total)Delta II crasher stage 1.33 km/s dVDragon II lander (1750kg prop burn) 0.54 km/s dV (1.87 dV total)Landed Lunar payload: 1000 kgSame scenario as above but taking the Delta II US based crasher lander to all the way to the surface to be refueled, saving some Dragon 2 prop for initial ascent, landed lunar payload: 300 kgIn this scenario availability of more efficient but non man-rated cargo landers could deliver the necessary 6000kg of prop for a man-rated Dragon2 + ascent vehicle to return to Lunar orbit. A overall cost reduction could be seen here as a lunar base evolves.Another option instead of using the AJ-10 (ISP=319s) is the Aestus upper stage engine, a pressure fed N2O4/MMH engine used in the Ariane 5G upper stage with an ISP of 324s. The big advantage here being common prop to the Dragon 2 lander to support refueling in a reusable lander. The turbo pump fed but not yet in operation Aestus II could further enhance capabilities of the system with an ISP of 340s.
So in this scenario the multistage lander is still pieced together in LLO? Seems a bit of a stretch to what has been done to date.
And no, you don't integrate anything off Earth. You dock with Orion, do the mission to the surface and back, and discard.
Quote from: Space Ghost 1962 on 02/25/2017 11:37 pmAnd no, you don't integrate anything off Earth. You dock with Orion, do the mission to the surface and back, and discard.What launch vehicles would be allowed? Just commercial or a second SLS?Without docking to a crasher stage in orbit, or some in space prop transfer, or high ISP cryogen propulsion I just don't see how a Dragon 2 (nevermind the heavier Starliner) could possibly work.The Apollo Lunar Module was 15200kg total mass in Lunar orbit. The ascent vehicle was 2150 kg dry. That is about what a single FH can place in lunar orbit, meaning a crew dragon would need to lose 2/3 its mass operating as a 2 stage Lander/Ascent vehicle to fit those constraints
The price of a "crasher stage" is to eliminate reuse as a possibility, for the benefit of accelerating a development program. As both LEM/LM and LK-1 (derived from Soyuz and using a crasher descent stage) attest to.
Quote from: Space Ghost 1962 on 02/26/2017 07:18 pmThe price of a "crasher stage" is to eliminate reuse as a possibility, for the benefit of accelerating a development program. As both LEM/LM and LK-1 (derived from Soyuz and using a crasher descent stage) attest to.Not necessarily. The crasher stage in the scenarios I listed is only to provide for a two way trip, and could be eliminated by refueling the stacked Dragon capsule and ascent stage in LLO and lunar surface.
So reuse could be phased in as more capable vehicles get developed, but the concept listed gets the ball rolling on manned landers with minimal development cost. -Start with a single Dragon 2 and crasher trunk integrated stage to land a cargo/surface "lab" type of mission.
-Initial manned missions use a LLO docked crasher descent stage to land a Dragon 2 & trunk integrated ascent stage this doesn't need to separate.
- Follow up missions can refuel the D2 & ascent stage, along with a new crasher stage.
Shouldn't landers/ascent vehicles be minimal for safety and cost? Like the size of the Soyuz descent module, maybe with more seats. A pre-landed uncrewed habitat (never to be launched from the Moon) within walking range could support them while on the surface. And another habitat in Lunar orbit for the transfers.For sustainable presence on the Moon one should not launch more stuff than necessary from it, but accumulate landed useful mass there.
Pressure fed.
Quote from: GWH on 02/28/2017 07:08 pmPressure fed. How does that work in zero-g? What keeps the liquid between the orifice and the pressure boundary?Is the propellant in a bladder?