One of the few good legacies of the W administration may be the refocusing of NASA's human spaceflight program on exploration--leaving Earth orbit and establishing ourselves beyond this planet. I say 'may' because, for a variety of reasons, it has yet to happen.
First we need to use our shuttle fleet for finishing the International Space Station, repairing and upgrading Hubble, and launching the Alpha Magnetic Spectrometer. Secondly, we need to complete a new launch architecture that can fulfill the mandates of Bush's Vision for Space Exploration (VSE). NASA's is developing the Orion spacecraft and Ares launch vehicles for this purpose, though they must wait until the shuttles retire in order to pay for them. Then, finally, we need to embark on missions that will sustain the program and catalyze further exploration.
It's that last part--the actual missions--that is tricky. The VSE puts forth the Moon as the prime destination and only after, Mars (it's mentioned as a brief afterthought). I was disappointed that Carolyn Porco in Wired's 2008 Smart List (15 people the next president should listen to), basically endorsed the VSE as-is. The person the next president should listen to on space policy is instead Robert Farquhar. In a recent issue of The Planetary Report (XXVIII.2) he detailed an alternative to the as-is VSE that has substantial advantages.
Basically, Farquhar's plan is a stepping-stone approach that builds infrastructure for expanding outward. The first destination is a spot in space beyond the Moon that is gravitationally balanced (the Sun-Earth L2, or second Langrangian, point). This point is the planned location for the next-generation space telescope, the JWST. Other telescopes are currently planned for this destination, so there is some incentive to have the capability to send astronauts there.
He envisions a "Deep Space Shuttle" that would ferry astronauts and equipment between Earth and L2, and an "Interplanetary Transfer Vehicle" that would swing by L2 and out to Near-Earth asteroids or Mars. The DSS, despite the name, has no hardware in common with our current Space Shuttles; it is a pure spacecraft, a re-usable "taxi" that doesn't need to fly through an atmosphere. It does month-long circuits; presumably, the space station could be the staging point for outbound astronauts.
The best part is that L2 can be used as a hub for destinations in the inner solar system. The cost and energy savings versus going down to the Moon and back are considerable. The ITV could use gravity-assisted flybys of the Moon for further savings on its circuits in to, or out of, L2.
This plan has a lot going for it. There are real economic incentives such as the ability to service telescopes and determining the feasibility of asteroid mining. Telescopes have also been talked about for the Moon; large, expensive projects utilizing the far side. It's also possible that one day, lunar soil could be a source of fuel; namely, tritium for fusion reactors. Needless to say, that is still in the realm of science fiction. This Near-Earth plan by contrast has smaller, simpler, more achievable goals, each of which builds upon the previous. This staging infrastructure could also be used to intercept asteroids on Earth-crossing trajectories, steering them away from potential impacts.
Another feature I like is that the plan lends itself naturally to international cooperation. The International Space Station has shown that such cooperation is not only possible, but that such large projects likely would not happen otherwise. It is extremely doubtful that we would have the political (not to mention financial) will to complete the ISS on our own. In the Farquhar plan for instance, the Europeans could build the ITV just like they recently completed the Jules Verne ATV, while we could collaborate with the Russians on the DSS.
And, ultimately, it is a more workable path to Mars. The Moon may become an Antarctic-style outpost, but Mars can provide humanity's second world. There is a fork in the road, one leads back to the Moon and the other is an outward spiral leading to a richer set of destinations including Mars.
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