As everyone know, the space shuttle mission ends today. At this point in time, NASA has no accepted mission that will return us to outer space in the near future.
Bearing in mind that space exploration is terrifically expensive, it seems to me that in our current economic state, we should be especially prudent with the choices that we make in terms of new missions.
I would also like to take it as read that NASA should be provided with new missions. The technological advances and national inspiration that the people of NASA have provided to the United States are one of the major themes of our history. It is unthinkable that NASA should be dissolved.
Since my youth, I have been a sci-fi dreamer. I cut my reading teeth on piles of cheap paperback editions of Asimov, Heinlein and Herbert. As a result, my consideration of the future typically involves humans in far away places, able to travel astounding distances in reasonable times.
Here are three things that I think we should be considering as new missions for NASA.
1) Establishment of sustainable deep-sea habitat for humans
Water is absolutely necessary for humans. There is no acceptable long-term habitat for humans that doesn't include large amounts of water. If you consider even the possibility of establishing of a colony of humans on another planet, then that planet will must needs have water.
Also, in the case that the atmosphere of that planet may not be immediately suitable for humans, or that radiation from a nearby star may be too strong, a submarine existence is preferred. Water is an excellent radiation shield, as we recently were reminded of with the Fukushima Daiichi nuclear reactors.
I know to some that this won't seem ambitious enough, as the lifeline to the rest of us will be short. But deep sea existence can be as unhospitable as outer space or a foreign planet. I believe that there is much to be learned from this exercise.
We haven't learned to establish a sustainable habitat for humans on regular land yet. I think that it isn't too far outside of NASA's purview to investigate this.
2) Development of economical, electric flight
The National Aeronautics and Space Administration: let's not forget that a serious part of NASA's mission is heavier than air flight. NASA could be working on flight power and structures that can be supported by renewable energy sources.
Heavier than air flight is expensive, and current commerical technology relies on highly enriched petroleum to exist. Without oil, humans stop flying pretty much immediately.
Common batteries are iron-based and heavy. Any motive energy source for electric flight will be necessarily high density and low weight.
3) Investigation and incubation of renewable energy generation and storage
It's silly to think that we'd be able to colonize another world that had both plenty of water and lots rich hydrocarbon energy deposits. We need energy to adjust prevalent conditions to match our biological needs.
I think that NASA could, and should, be instrumental in humans learning how to sustainably colonize Earth. If we learn how to do that, we'll be alot further along toward learning how to colonize a different planet.
What else?
These are just some ideas that I have. And I certainly won't say that I've considered everything. What did I miss?