- D2 + trunk + MUS take off from moon on a direct flight to Earth.
Quote from: MikeAtkinson on 02/20/2017 09:49 pm- D2 + trunk + MUS take off from moon on a direct flight to Earth.Taking the TEI propellant from LLO all the way to the Lunar surface and back to LLO is a huge penalty since it requires 4 km/s of delta-V. Better to leave the TEI propellant in your tanker and have the D2+trunk+MUS dock with the tanker after liftoff from the Lunar surface.
1. Fuel rich ...
Why place all the dV requirements for ascent/descent on the lander, and in doing so drive up the requirements on the lander significantly when an upper stage can do the work here?
A Xeus-Centaur is at least partly off the shelf, IVF is scheduled to be demo'd in 2018. Investment in that area would have a much greater return IMO then trying to make a capsule perform a 2-way trip. Also meets criteria of a future, reusable lander.
The canted engines on Dragon 2 might not be so disadvantageous if they are providing the final landing control of the stack. Trunk mounted engines for the caspule/return would still be required.
- Instead heavily modify the 2nd stage (still using Merlin 1D vac)--- Add landing legs--- Add refueling capability--- Add long duration capability ----- keep the LOX cold----- keep the kero warm----- power from the trunk
- Tanker version of second stage- Tanker 1 launched into LEO on FH- Tanker 2 launched into LEO on FH, refueled by tanker 1.- Tanker 2 does TLI and inserts into LLO (uses modified trunk for power).- Tanker 3 launched into LEO on FH.- Tanker 4 launches into LEO on FH, refueled by tanker 3
- D2 + trunk + modified upper stage (MUS) launches into LEO on FH, refueled by Tanker 4.- D2 + trunk + MUS does TLI and inserts into LLO- D2 + trunk + MUS refueled from tanker 2- D2 + trunk + MUS land on moon- D2 + trunk + MUS take off from moon on a direct flight to Earth.
- D2 + trunk separate from MUS- D2 and trunk separate shortly before landing. - modified versions of this can place heavy cargo payloads on the lunar surface.- modified versions of this can use other launchers for the tankers.- modified versions of this can use other means to get fuel into LEO.- future version could produce LOX on the lunar surface.
- the tankers could be launched by SLS, in which case we have 1 launched to LEO to refuel the D2 stack there and/or another launched to LLO for the second refueling (I don't see how this could be cost effective).- Alternatively, the D2 + trunk + MUS could be launched by SLS to LLO (MUS does insertion burn) and then refueled from a tanker launched on a second SLS (again I don't see how this could be cost effective).
- This develops refueling capability, could use a shakedown mission in Earth orbit and/or lunar flyby, not much point in sending the stack to ISS (and probably would not be allowed anyway). Crew stays with D2 the entire time, and can use D2 abort capability at launch and retropropulsion landing.
This would I think have a low development cost (well under $2B) and per mission costs in the order of $700M. Using SLS would increase per mission costs to at least $1500M
Unfortunately, it does not quite meet the brief. Fuel rich architectures really hurt SLS because it costs so much to launch. To make this architecture work a high flight rate for FH would be required, and ideally from 2 launch sites, IF SpaceX could demonstrate 2 week turnarounds and use 2 launch pads. A design like this would place the D2 a long way above the ground, not exactly easy for egress.
Perhaps the Trunk could have a ‘Propulsion Pallet mounted within it – 2x fuel, 2x oxidizer and 2x helium pressurization tanks; supplying a cluster of Draco thrusters (6 or 8?) mounted in the center of the Pallet, or 1x Super Draco, throttled down and with or without a nozzle extension.
Would it need about 2km/s delta v to insert into Lunar orbit and leave on an Earth transfer orbit X days later, or a bit more?The Dragon meets the LM Dragon waiting in lunar orbit, the crew transfers and then it’s time for P.D.I. (Powered Descent Initiation).
My concern is that SX/Boeing are not up to the task of appropriate lunar lander propulsion here. Convince me otherwise please.
Quote from: Space Ghost 1962 on 02/21/2017 03:12 pmMy concern is that SX/Boeing are not up to the task of appropriate lunar lander propulsion here. Convince me otherwise please.How about using spare Aerojet OMS leftover from the Shuttle program? SX/Boeing could incorporate it in their designs.
Outside of the AJ10 and derivatives, there is a need for qualified hypergolic engines for both concepts.My concern is that SX/Boeing are not up to the task of appropriate lunar lander propulsion here. Convince me otherwise please.
AeroJet Rocketdyne is more of a caretaker of older technology at the moment. (RS-68 being their last real development, 15 years ago)
Quote from: Lars-J on 02/21/2017 11:33 pmAeroJet Rocketdyne is more of a caretaker of older technology at the moment. (RS-68 being their last real development, 15 years ago)What about J-2X? They have also been given the contract to develop RS-25E and are developing the AR-1.
J-2X didn't go so well, did it? Over budget/schedule, underperforming, and shelved.