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Review: Centauri Dreams

Centauri Dreams: Imagining and Planning Interstellar Exploration
By Paul Gilster
Copernicus Books, 2004
Hardcover, 302 pp.
ISBN 0-387-00436-X

The capability to travel across vast distances of intergalactic space has been the subject of novelists and filmmakers as well as physicists and engineers for many years. In terms of popular culture, both TV and films have displayed the need to travel across space at astounding speed; Star Trek and Star Wars certainly popularized space travel at light speed and beyond.

During the manned Apollo missions to the Moon, a maximum of 40,000 km/hr was sufficient to get there in roughly three days. For those future missions to Mars and beyond envisioned in the new Vision for Space Exploration, liquid hydrogen and oxygen as propulsion fuels may not measure up to the task. Something far more advanced and powerful will certainly be needed for journeys beyond Mars. That something is the subject of Paul Gilster’s book, Centauri Dreams.

The nearest star to our solar system is Alpha Centauri, about 4.3 light years away. A light year is a convenient means of distance measurement because conventional means in miles or kilometers is so large as to thwart true appreciation. Gilster states that Voyager 1 is traveling at a speed that could take it from Los Angeles to New York in four minutes. However, at that speed, it would take over 77,000 years to reach Alpha Centauri. Scientists and engineers have been working on that interstellar propulsion quandary for many years at various NASA field offices as well as at universities around the world. The goal is one-tenth light speed, roughly 30,000 kilometers per second. How can an interstellar probe achieve this speed?

Voyager 1 is traveling at a speed that could take it from Los Angeles to New York in four minutes. However, at that speed, it would take over 77,000 years to reach Alpha Centauri.

First, the question of “why?” must be answered. Although research into this subject had been going on for years, it was the successful landing of Mars Pathfinder and its successful but limited robotic mission in July of 1997 that sparked NASA to pursue bigger goals. That month NASA administrator Daniel S. Goldin announced building a robotic probe to reach another star would be a new goal for the agency. “We have to set goals so tough it hurts—that it drives technology—in semiconductors, materials, simulation, propulsion,” he said.

The topics explored by Gilster are nothing short of fantastic, but we are less incredulous of their achievement than any previous generation. The pioneers of flight could not conceive of shattering the speed of sound, yet it was achieved 44 years after Kitty Hawk. Today’s combat aircraft do this routinely. What interplanetary and interstellar speeds will be routine 50 years from now? There are several technologies being investigated to achieve this. Chief among the propulsion concepts being pursued is antimatter—no joke. “More than plausible,” Gilster writes, “antimatter is real, it is being produced [although minutely—ed.], and is under active investigation.” Solar sails are covered, as well as light sails, or laser sails, ramjets, and “fusion runways”.

There are other issues as well. Scientists working on these ideas and missions will probably never see them accomplished because the probe will take more than 40 years to get to Alpha Centauri. The people Gilster interviewed accept this fact. Communications take so long at these distances the probes must have intelligent autonomous systems and even self-repairing capability. The real payoff in present terms is the spinoff technology that will be used for future lunar and interplanetary missions. Gilster’s book is a fascinating read into the realm of the fantastic and the achievable.