Copyright 2022 Robert Clark
In the blog post Possibilities for a single launch architecture of the Artemis missions I discused that a single launch architecture is possible for the SLS rocket if there is a lightweight lunar lander. Such is possible using currently existing space stages. Firstly, a lunar crew module of ca. 2 ton mass is possible based on Orbital Sciences Cygnus capsule, discussed in Budget Moon flights: lightweight crew capsule. The Cygnus is actually build in Italy by Thales Alenia Space. As it is already built, the additional modications for added life support would be comparatively low cost.
Note Thales Alenia Space is already adding life support sysmtems to a larger version of the Cygnus for the lunar Gateway. Then a lower cost version would simply use the smaller Cygnus itself, at a ~2 ton dry mass for a short term stay on the lunar surface.
As for the propulsion system, the earlier Ariane 5 EPS storable propellant upper stage prior to the current cryogenic upper stage could be used for the purpose: it had a 1.275 ton dry mass and 9.750 ton propellant mass, for a 11 ton gross mass. Then the crew module and propulsion stage would mass 13 tons.
An advantage over the SpaceX Starship lunar lander plan is that it is only 3 meters high, the same height as for the Apollo lunar lander descent stage, making it easy for the astronauts to climb down to the lunar surface, compared to the 25 meter height for the Starship.
Calculation.
The delta-v to the lunar surface from low lunar orbit is 1,870 m/s:
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The middle size version has a dry mass of 3,955 lbs, 1,800 kg, and propellant load of 25,064 lbs, 11,400 kg. It has an Isp of 316 s. Then with a 2 ton crew module it would have a delta-v of 4,300 m/s:
316*9.81Ln(1 + 11.4/(1.8 +2)) = 4,300 m/s, sufficient for single-stage lunar lander.
Robert Clark
1 comment:
Artemis does not plan to use low lunar orbit, they plan on using that elongated (and slightly unstable) "halo" orbit and that Gateway station thing. Not counting the plane change to reach polar (to go to the south pole where the ice might be), and not counting any budgets for rendezvous and docking with the Gateway station, the one-way delta-vee is not at all comparable to that for Apollo, it is actually above lunar escape. If you make the lander single-stage to be reusable, it needs at least about 5 km/s delta-vee capability, or about half that per stage if a non-reusable two-stage (could recover and reuse the upper stage). 5 km/s in one stage at a more-than-insignificant payload fraction is challenging for LOX-LH2, and is a practical impossibility for storables. These vehicles will require structural robustness and big landing legs; their inert fractions will be above 10-15%. -- GW
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