I won’t lie to you: even some of my space-minded friends think it’s a bit impractical to hold a workshop on sending robots and humans to other star systems. Mostly it’s about practicality: “We’re trying to keep SLS funded!” “It’s difficult enough getting to the moon!” “That’s science fiction!” Of course going to orbit with a heavy-lift launch vehicle or sending humans to the moon was once the stuff of science fiction, too.
But seriously: why talk about the stars when we’ve not yet sent humans beyond Earth orbit since 1972? We’ve got some robots out at the edge of the solar system, toying with the dust between the stars, and one machine is racing toward what used to be called the farthest planet, Pluto. Space travel is difficult. It’s expensive. We’re working on more near-term projects right now. And there are important, serious problems affecting our nation and our planet right now. All true. Practical concerns fill our days, and they're often serious.
So let's talk practically. We have energy concerns. Food production takes energy. Transportation requires energy. In fact, most of what we do, from communication to fertilizer production, requires energy of some sort, and energy is a problematic commodity because of its by-products (smog, smoke, and carbon dioxide for petroleum; radiation and thermal pollution for nuclear). A lot of petroleum can be found in unstable parts of the world that don't like the United States too much. And there are a lot of people in the world who would like to live as well as Americans, with access to plentiful food, clean water, and cheap energy. Energy from space can address that problem. The Earth receives 1,365 watts per square meter at this distance from the sun. We're starting to capture some of that energy on the ground, but that solar energy is filtered by our atmosphere, and the Earth rotates and puts up interesting weather (clouds), which block that energy. Solar energy in space is on all the time, and it's relentless.
Our economy is dependent on satellites: communications, finances, weather reporting, military operations, resource management, ATM cards, air freight services, and many, many others. Do we need better satellites? Yes. And we need to improve our ability to get those satellites into space more cheaply. As my friend Les Johnson put it, "We [space advocates] have succeeded: our economy is now addicted to satellites." Take them away, and our economy would collapse.
And while we're at it, if we can get satellites up there more inexpensively, we can do other things, like move dangerous asteroids out of the way. We don't want to end up like the dinosaurs. We don't want (as Robert A. Heinlein put it) "all our eggs in one basket." And while we're moving those asteroids, we might want to consider mining them for the metals and water that are inside them--for use in space or for eventual export to Earth. We have deep-pit mines the size of asteroids on our world, and they leak a lot of unpleasant things into our environment. It would be nice to do the mining out in space, on high-radiation rocks with no atmosphere or people around. Stop a mass extinction, clean up the environment: those are things humanity can support, yes? From an energy, environment, and economic perspective, long-term access to space is a practical activity.
Yet we need to keep our eyes on the stars.
Our telescopes are discovering other worlds around other stars. Earth is not the only planet in the universe--eventually we might (I'd say will) discover that it is not the only one with life on it. We need to learn about that life because that's what we do. If it's intelligent life, we have even more challenges ahead, but a productive, challenge-minded humanity with a multi-world civilization would be much better able to cope with it than one world and limited horizons. Interstellar travel is the ultimate expression of humanity's willingness to challenge and improve ourselves. We can apply the lessons learned in exploring and using the resources of space to improve our home world. If we try to go, we will be saying as much about ourselves as if we stop.