Current Administration space policy calls for NASA to look beyond the “been there, done that” of the Moon.

From a policy perspective, that is arguably a wise decision. By returning to the Moon, NASA might easily end up stuck in an “ISS 2 on the Moon” situation.

There’s also a technological argument against returning to the Moon, however. Returning to the Moon would require developing a lunar lander, a new piece of a single-purpose hardware that would make lunar landings more expensive than missions to, say, an asteroid. But is that assumption necessarily true?

Under the Bush Vision of Space Exploration, NASA was planning to spend around $10 billion to development the Altair lunar lander. That’s certainly a significant amount of money – several times what SpaceX expects to spend to develop both the Falcon rocket and the Dragon capsule – but NASA was proposing (not unexpectedly) to build the mother of all lunar landers, rather than a minimal cost system. Since we now know that’s unrealistic, what sort of lander options might be affordable, either for NASA or private industry?

Surprisingly, there are a number of possibilities which, if not quite off-the-shelf, are fairly close.

The most obvious possibility is the Morpheus lander, built by Armadillo Aerospace, which NASA has been testing at Johnson Space Center.


Morpheus has successfully completed a number of tethered tests at JSC, and NASA plans to move it to Kennedy Space Center to begin free-flight tests in the near future. (There’s undoubtedly some political dimension to the move, since there are plenty of locations in Texas which are as suitable for free-flight tests as Florida.)

Morpheus is designed to land 500 kilograms on the Moon, although it does not currently have an assigned mission. (Again, that is more for political reasons than technical reasons.) Morpheus was designed  for unmanned missions. Still, it would not be a huge step from the current Morpheus configuration to an unpressurized, open-cockpit lander similar to what Johnson Space Center proposed in the Human Lunar Return study of the early 1990’s.

NASA Human Lunar Return open-cockpit lander

Open-cockpit lunar-lander concepts have a long history, dating back to the “bug” proposed for Gemini lunar-landing missions in the 1960’s. Although open-cockpit landers appear unconventional to those who have seen Apollo, the idea has some merit, especially for early, cost-constrained flights. Any astronaut going to the Moon is going to require a pressure suit, anyway. On the other hand, it makes little sense to haul a pressurized habitat all the way to the lunar surface merely to carry it back into orbit again. The goal, if you’re trying to build a lunar base, is to *leave* things on the surface. That is what JSC proposed in the HLR study, which included an inflatable habitat that could be carried atop the lunar-lander platform.

One obvious problem is that Morpheus is designed for one-way missions. The 500-kilogram payload is more than adequate for a single astronaut, but to take off again would require considerably more delta-v. That could be accomplished by scaling up the vehicle or using higher-performance propellants. The HLR lander, for comparison, was designed to carry 1,775 kilograms on a one-way mission to the lunar surface or two astronauts to the lunar surface and return, making it about three times the size of Morpheus. Although that is a large step up from Morpheus, it is not a huge one. (If the lander were designed for a single astronaut, rather than two, it would be a much smaller step.)

Another option which might be considered is SpaceX’s Dragon capsule.

SpaceX "Red Dragon" Mars landing

SpaceX’s Red Dragon concept is usually shown in the context of Mars (as in this illustration). SpaceX CEO and chief designer Elon Musk has stated, however, that Dragon can land on any body with a solid surface.

Unfortunately, Dragon has the same limitation as Morpheus – it can land but not take off again. Perhaps that is good enough, however? Perhaps Dragon might be used to deliver a smaller, open-cockpit ascent stage derived from a vehicle like Morpheus. The Dragon capsule itself is large enough to be useful as part of a lunar base, so it would make sense to leave it on the surface. In the early days of lunar settlement, transportation requirements will be dominated by down-mass, with up-mass limited to smaller items (principally samples and returning crew). That will change, of course, if and when export-mining operations begin, but mining is still some time in the future.

A third option would be the Xeus concept, which would adapt a Centaur upper stage like the one shown below. Four auxiliary rocket engines would enable Xeus to land on the lunar surface in a horizontal position. (Landing a rocket stage in a vertical position is theoretically possible but makes cargo handling more difficult, especially in a location like the Moon where there are no cranes handy.) Xeus is being developed by Masten Space Systems in cooperation with United Launch Alliance, the Boeing-Lockheed joint venture which markets the Centaur.

Centaur upper stage

Xeus could carry 5 tons of cargo to the lunar surface and back or 14 tons on a one-way mission.

One possible area of concern for all these vehicles is landing gear. Armadillo Aerospace experienced landing-gear problems during the Northrop Grumman Lunar Lander Challenge. Scaled Composites had a gear failure during the SpaceShip One flight-test program. The landing gear in the SpaceX Red Dragon illustration appears rudimentary. (Fortunately, the artist has shown it landing on conveniently flat terrain.) Landing gear was a major concern, and the subject of much research and development, during the Apollo program.

Landing gear might be an area where a little bit of innovative R&D spending could have a large payoff. Perhaps NASA’s Centennial Challenges program should consider a robust landing-gear competition. NASA could challenge teams to build landing gear to a specified weight. The gear would be attached to a weighted box full of accelerometers, telemetry, and breakable test objects, then drop-tested from increasing heights until the gear fails. This competition could be fairly cheap. It wouldn’t require building or flying any rockets. So, the prize purse might be relatively modest, perhaps under a million dollars. This would seem to be a low-risk, high-payoff investment for NASA, assuming Centennial Challenges has any money left in its budget today.

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    James R. Hopkins commented

    This is an interesting dilemma, but what would happen if ISRU propellants are available on the Lunar surface to refuel the vehicle. What happens to the problem then?

    October 2, 2012 at 7:10 pm
    Robert Clark commented

    Nice post. The Morpheus program has succeeded beyond what NASA even intended. The program lead has said it can be scaled up to produce a manned lander. Considering the low cost of the Morpheus program so far, the manned lander might only cost a few 10’s of millions of dollars, compared to the $10 billion Altair lander.
    We can return to the Moon and affordably. NASA simply has to choose to do so.

    Bob Clark

    June 24, 2014 at 9:45 am