August 3, 2009
The Moon versus Mars controversy has reared its ugly head yet again. For the newcomers, this is the perennial “debate” among space buffs about what the next destination in space should be. I do not mean to suggest that all possibilities are encompassed by these two options; it just seems that most advocates fall into one or the other of these two camps.
In part, this argument has arisen because the Augustine Commission, currently deliberating the future of NASA’s human spaceflight program, has resurrected the debate with an architectural option they call “Mars First” (a.k.a. Mars Direct, Direct to Mars, Apollo to Mars and Mars-in-MY-lifetime), beloved of the Mars Society and ex-astronauts everywhere. Briefly, this plan calls for sending people to Mars as soon as possible – no Moon, no asteroids, no L-points: do not pass “Go,” do not collect $200. In such a scenario, all pieces of the Mars mission are launched directly from the Earth; this roughly one-million-pound on-orbit mass includes all the propellant needed for the trip, which makes up about 85% of the mass of the spacecraft.
The Mars First option follows the “Apollo template.” In 1961, faced by the political necessity to get men to the Moon and back within a decade, Wernher von Braun designed the biggest rocket he could imagine – basically a scaled-up, clustered V-2 – to lift all of the parts he needed into space. This super heavy lift vehicle was actually a family of rockets (Saturn class), whose ultimate behemoth was the Nova, a vehicle with a lift-off weight exceeding 13 million pounds. Fortunately, the choice of lunar orbit rendezvous for the Apollo mission mode made Nova unnecessary and a self-contained mission was launched by a single, smaller (7 million pound) Saturn V.
The Apollo template makes use of maximum disposability. As the mission proceeds and each flight element is thrown away, unused and unusable, the vehicle gets smaller and lighter. For some items, such as fuel tanks and structural elements, this doesn’t introduce unwarranted penalties, but some parts of the vehicle are high in cost and value. Within the Apollo template, however, their loss is inevitable.
A significant part of the Apollo template is the lack of infrastructure legacy, i.e., the elements brought to a destination that are available for use by the next crew. We need to develop an architecture that leaves equipment in place for future use and expansion by subsequent visitors. This is one reason why sortie missions are inferior to establishing an outpost or a base; sortie missions spread surface assets over a large area where they cannot mutually support each other.
Much of the support for Mars First comes from the belief of its advocates that we will get “stuck” on the Moon or somewhere else, sort of like we have been “stuck” in low Earth orbit for the last 40 years. In their minds, Mars is THE destination. To hear the pitch, one might believe Mars has it all – atmosphere, water, a 24 hour day, and possible ancient fossil life. Adventure! Thrills! What else could a space cadet want?
Although the “Mars First” advocates vigorously present their position each and every time the direction of our space policy is debated, they have never won the argument. Why? Is it some evil conspiracy to keep them from their Mars dream? Is it just the stupidity of policy makers? Some simple facts suggest otherwise.
We do not now have the technology we need to support multi-month, self-sufficient human space travel. The International Space Station needs nearly constant servicing and re-supply from Earth. In fact, one of the missions of ISS is to learn how to live in space without such service and re-supply, closing the various life-support loops and thereby developing sustained human presence. This is experimental technology and not nearly mature enough upon which to rest the lives of a Mars mission crew. Regardless of claims, a Mars mission is at least one (and possibly two) order(s) of magnitude more costly than any alternative mission.
There isn’t the will in either the Congress or the Executive to significantly increase the amount of money allocated to our national space program. Spectacular claims about “exciting the public” with a human Mars mission, regardless of their veracity (which is doubtful), do not translate into higher budgets for NASA. To go to Mars using existing technology, with an Apollo-style business model, is both unachievable and unaffordable.
The Vision for Space Exploration makes Mars a goal – along with every other space destination – after we go to the Moon to learn how to live and work on another world. Moreover, the VSE implicitly states that such is to be accomplished under existing budgetary envelopes. In contrast to the Apollo template, time rather than money is to be the free variable. The Moon can be reached with existing launch assets; although NASA is currently bogged down in a debate about rocket development, the real issues are how you go back to the Moon and what you do there. The Moon offers the material and energy resources to develop the technology and skills necessary for sustained, long duration capability in space.
Mars First advocates worry about getting “stuck on the Moon.” In fact, it is their obsession for Mars that has kept us in low Earth orbit for the last 40 years. By relentlessly pushing for a space goal that is well out of our technical and fiscal reach, they have gotten an undesired (but not unexpected) result: stasis. There is no choice. You use the Moon or you get nothing. Right now, Mars is a bridge too far – we need the stepping-stone of our Moon to reach it.
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