After recently winning the Orion CEV contract, Lockheed Martin is looking to the future, with a new study exploring a variety of possible Lunar Surface Access Module (LSAM) strategies and configurations.The study explores three unique ideas for using a LH2/LOX fueled LSAM to facilitate VSE (Vision For Space Exploration) lunar landings.
The superb Lockheed Martin Lunar Landers Presentation is available to download on L2.
**Click here for larger, selected images, showing the three concepts**
The thrust of the new report is a focus on adapting LOX/LH2 landers for simple use as a lunar transportation system. LOX/LH2 is extremely efficient and can be used both for providing electricity and water in fuel cells – and in conjunction with a lunar ISRU system. However, because LH2 is so bulky and the high area ratio LOX/LH2 engines are so long, it has been difficult to design effective landers that use LOX/LH2 in their propulsion system.
The lander uses an existing single LOX/LH2 pump-fed RL-10 engine for most of the descent and uses low thrust, highly throttleable, pressure fed hypergolic engines to perform the final landing. Once on the surface, the crew performs EVAs via an inflatable airlock, eliminating the need for extremely long ladders. The crew can access cargo once on the surface via 10 200-kg side rack cargo pallets. The Dual-Thrust Axis Lander offers large gimbaling solar panels and 28 m^3 of habitable volume on two decks. The vast residual LOX/LH2 from the Descender stage are sufficient to power lunar operations through the lunar night.
The vehicle has some mass penalties compared with the Dual-Thrust Axis Lander, because it cannot use the LOX/LH2 for power generation and must incorporate all of the electricity and life support systems onto the ascent stage. Therefore, the Retro-Propulsion Lander is only appropriate for missions that do not exceed seven days in duration, or for longer missions to an emplaced lunar base.
Also, when accessing a lunar base, wheels offer a number of advantages. Cargo and crew landers will have to land several hundred meters from the base to avoid damage deployed elements. A wheeled lander offers significantly easier transport of large cargo elements rather than having to haul them up to a kilometer to the base. This also prevents a ring of spent landers building up around the base; instead, each lander could be towed or driven to what the study calls a ‘boneyard’ of spent descent stages. The Dual-Thrust and Retro landers only are meant to be towed, but motors could be easily added.
The single-stage lander could be completely reusable if it were refueled in lunar orbit with propellant from Earth, or on the lunar surface from locally derived LOX and LH2. Reusability also prevents dozens of discarded descent stages from building up around a lunar base.
The single-stage lander has some disadvantages as well. The crew cabin is very small and quite far from the surface; therefore, the study recommends this design for ‘outpost support missions’ so that the crew would not have to live in the lander cabin. The single-stage lander has a cargo bay on bottom, but is not as well-suited to delivering large monolithic cargo elements as are the first two designs.