Centauri Dreams: Imagining And Planning Interstellar Exploration

Rating:
Summary: Not just the stuff of dreams...
Review: It will be surprising to many people that the initial planning of humanity's first voyages to the stars has already begun. Those of us who grew up in the early days of the American space program, and whose vision of the future assumed that by the end of the twentieth century space flight would be commonplace and relatively easy, and who assumed that manned missions to Mars and further would be the next step within several years after the Apollo moon landings, became impatient with the slow and methodical pace of space exploration carried out in the immediate vicinity of Earth and by robotic probes sent about the Solar System- even though these missions were usually brilliantly planned and executed.

This book brings the welcome news and consolation that, even though the first interstellar mission of any kind is probably still at least several decades away, imaginative and intelligent people are already working on the theoretical basis for such future voyages, and some of the engineering problems are being addressed. So at least we don't have to wait until the rest of the solar system has been explored to get an idea of how the next colossal task will be approached. Much of this work is being done by various research agencies associated with NASA, by the European Space Agency, and even by academics and assorted dreamers.

Paul Gilster does an excellent job of explaining the current state of the planning for adventures to the closest stars, providing lucid descriptions of the work even now being done on such amazing concepts as laser-powered sails and antimatter drives. I have read a fair number of the popular scientific works intended to introduce laymen to difficult subjects (string theory, hyperinflation, etc.), and this volume is at least as clear and readable as anything I have seen by Allan Guth or Brian Greene. Besides being a primer, however, Centauri Dreams is also a fine piece of investigative reporting, since the author discusses the people who are doing this imaginative work and places their endeavors within an institutional context to show some of the bureaucratic and political hurdles that must be overcome.

Mr. Gilster also relates interstellar planning to the development of notions of interstellar travel within science fiction, showing how fictional (and often very much misguided) thought has influenced scientific thought.

Centauri Dreams is an exciting and important read. Highly recommended.



Rating:
Summary: The meek inherit the Earth, the rest of us go to the stars
Review: This book is about sending a space mission to a nearby star. I know, it sounds more like science fiction than fact. We're talking about really long missions. Perhaps several hundred years or even a couple of thousand years. Even the one-way light time to our objective would be on the order of five or ten light years.

Gilster starts by mentioning some possible destinations: Alpha Centauri (closest, at 4.3 light years) and Epsilon Eridani (10.7 light years but may be more interesting biologically). Or possibly Barnard's star (5.9 light years) or even Tau Ceti (11.9 light years).

Yes, we could try to get a spacecraft to move much faster. But that's not easy. And there's a much, much higher chance for the spacecraft to be destroyed just by hitting a very small object. The author warns us that at such speeds, a grain of sand would look like a torpedo. Even if one of the speculative propulsion technologies the author then discusses could be made to work, the chance of the spacecraft surviving the trip might be rather small.

On the other hand, the author also tells us about space telescopes that will be looking for terrestrial planets in the next few years. What if one of them finds a planet that looks like it harbors life? Would we then start taking a mission to that planet seriously?

Still, how does one get there? Gilster explains that chemical rockets are unlikely to be the right answer. Even nuclear propulsion is too weak. The first alternative he suggests is antimatter. With all due respect, I find this idea preposterous. The next idea is a Laser Accelerated Plasma Propulsion System (LAPPS). While this idea might work in theory, present technology is several orders of magnitude short of being usable.

Next we get a technology that come a little closer: solar sails. The author discusses a 249 x 249 foot sail that is being built by L'Garde, a California corporation, that can take a 3-kilogram payload out of the solar system. It would take this sail 100,000 years to get to Alpha Centauri, which shows that with today's technology, we are about two orders of magnitude short of what we need for such a mission to make any sense. The author explains that with expected improvements in technology, we're likely to get one of those factor-of-ten improvements. But the next one will not be so easy. Nevertheless, this is the least speculative of the ideas presented in the book.

Gilster also tells of another (but more speculative) idea that might give us a similar speed, namely Mini-Magnetospheric Plasma Propulsion (M2P2), which is advocated by Robert Winglee at the University of Washington. This involves creating a "magnetic sail" kilometers in diameter which would hitch a ride on the solar wind. This idea needs much more work than a normal solar sail, but I think it is worth pursuing.

After this, we see a technology that would supply enough speed to our spacecraft if it worked: a laser-beam driven sail. All we need is 65 trillion watts of power on the ground! Plus the technology to deliver it to the spacecraft sail. And then get the craft to survive the flight. I guess all this is worth investigating, but this technology is nowhere near where it needs to be so far. At best it seems impossibly expensive.

The final portion of the book deals with some obvious problems: how do we communicate with the spacecraft when it is so far away? How will spacecraft navigation work? Or power? And best of all, how will the spacecraft maintain itself? What sorts of AI algorithms will need to be developed?

I found this book very interesting, but it does appear that it will be a long while before we have a successful mission to another star.