by Lou Friedman
|The best way to advance ideas for interstellar flight now was to accept that humans would be best left at home (or at least in our solar system).|
Interstellar flight is a vision for some and science fiction for others. I recall a discussion I had with Freeman Dyson a few years ago about whether we were further from interstellar flight than was Leonardo DaVinci from the airplane. I thought so. But DARPA, with a little cooperation from NASA, conceived an idea called the 100 Year Starship (100 YSS) to create an organization that would focus the vision by public engagement and technical studies about sending humans on the ultimate voyage. The Orlando symposium attracted over 500 people over three days discussing many aspects of interstellar flight (see “The journey of 100 years begins with a single weekend”, The Space Review, October 10, 2011).
At the kickoff meeting of the 100YSS last January I argued for more emphasis on robotic flight. The pace of human spaceflight technology advancement is far slower than that of robotic technology. Projecting those advances over 100 years opens up many possibilities for expanding human presence into the universe without humans having to be carried along. At the symposium I carried that message further asserting on a panel that the best way to advance ideas for interstellar flight now was to accept that humans would be best left at home (or at least in our solar system).
That assertion is unpopular, at least among the organizers of the 100YSS and in the interstellar flight community. Much of the emphasis at the symposium was on those themes which dominate science fiction literature: advanced propulsion with nuclear or antimatter technology not yet invented, generational starships on multi-century flights, cryogenically cooling the human passengers to minimize life support requirements, and exploiting unknown physics such as warp drives, black hole passages, and quantum communications. I love the literature and, more than that, I find it intellectually stimulating. But much (not all) of it seems a bit retro with many ignoring the real revolution going on in nanotechnology, genetic engineering, and artificial intelligence.
We (Tom Heinsheimer, Darren Garber, and I) presented a paper at the symposium about really small missions to take limited first steps on (dare I say) a flexible path beyond our solar system using just solar sails, which fly at very high speed due to their very large area-to-mass ratio and ability to dip in close to the Sun—less than a quarter of an AU. The very small mass spacecraft would eventually be instrumented with biological and nanotechnology payloads.
Whether your vision is sending colonies of big heavy humans or their robotic and nanobiologic emissaries creating virtual worlds with real data from other star systems, it is, as I said, mind-expanding. It also responds to the rationale that I think makes spaceflight so popular and ultimately important: who are we, and what is our destiny in the universe? We are ultimately searching for ourselves “out there.”
|I was particularly impressed at how useful it would be for astronauts to conduct space operations and science on even a small asteroid as littler as five to seven meters across—taking the first steps toward space mining and utilization of space resources.|
Less way out, but still a big idea, is to think about altering the solar system for our convenience by moving celestial bodies. Why would we want to move an asteroid toward the Earth? The idea was sparked when the flexible path into the solar system was recommended as a policy for human spaceflight. As President Obama said, it is time to go beyond the Moon, the human achievement of a previous generation. He proposed missions to a near Earth asteroid (NEA), then to the orbit of Mars, and then on to Mars. But even the first step is very large: the trip times are several months, life support requirements are considerable, and the problem of identifying a suitable target is significant. A precursor step might be to just dip our toe into the ocean of interplanetary space: just getting beyond Earth orbit, for example to one of the gravitationally stable points known in celestial mechanics as Lagrange points. But there is no “there,” there. If this is to be a human spaceflight mission it should be a place for astronauts to do both science and practice space operations.
This leads to thinking that, if the astronauts cannot reach the mountain, why not bring the mountain to the astronauts? Amazingly enough, JPL studies, using reasonably-sized solar-electric low-thrust systems, show that moving hundreds of tons of asteroid to a Lagrange point may be feasible in robotic missions of five to seven years. A proposal was made to the Keck Institute for Space Studies (KISS) by John Brophy of JPL, Prof. Fred Culick of Caltech, and me to examine mission concepts in a small study and in workshops. To the surprise of most of the 30 participants, the first workshop increased our confidence and interest in the idea. I was particularly impressed at how useful it would be for astronauts to conduct space operations and science on even a small asteroid as littler as five to seven meters across—taking the first steps toward space mining and utilization of space resources. One novel idea we came up with is to exploit the astrodynamics of invariant manifolds in combination with low-thrust trajectories. Another was to take that small asteroid off a bigger asteroid (pushing a boulder off a rubble pile, for example). That way we would have a much wider choice of carefully selected objects to use as our target.
One would think that idea of moving asteroids and creating an interstellar starship are unrelated, but during the 100YSS symposium, Dr. Joseph Breeden gave me a paper showing a clever way to put a binary asteroid on a close pass of the Sun and then have its smaller part end up on an interstellar trajectory.
Way out, to be sure, but these ideas are worth more consideration. We desperately need a path for humans and expanding our thinking may be the antidote to letting today’s problems and political constraints make us give up on ever sending humans anywhere. Both of these activities engage a new generation of space enthusiasts who may be able to figure it out.