Travel to the stars still science fiction


Space: Until the laws of physics are rewritten, a trip to Alpha Centauri will probably remain a journey of the imagination.

May 14, 1999|By Gwinn Owens | Gwinn Owens,SPECIAL TO THE SUN

LOS ANGELES -- In the 21st century Earth people may send manned expeditions to Mars. After all, we made it to the moon in this century so, obviously, Mars is next. Then, after Mars is ours, we soar into distant space, cavorting among alien worlds like bold freebooters of old. Right?

"Wrong," says Don Kephart. "We have been bedazzled by science fiction and Hollywood fantasy. A manned safari even to our nearest star is at least 1,000 times more complex and difficult than going to Mars, and even Mars is no pushover -- we will be lucky if we get there in the 21st century."

A star trip, on the other hand, will not happen in our lifetime, he says, and possibly never.

Kephart, a retired senior aerospace scientist in Los Angeles, is among an elite group of specialists who have spent part of their lives getting paid for thinking about the feasibility of this sort of thing. To talk with him is to realize that when we contrast the vast reality of the cosmos with the frailty of the human species, our space-travel fantasies come crashing to earth. He points out that only a total departure from the natural laws we now accept could provide a glimmer of hope.

In an effort to put to rest the illusion that flying to a star is just a little more challenging than a trip to the moon, Kephart offers this model:

Assume the earth is 4 inches in diameter, that is, grapefruit size. On that scale, the moon is a golf ball, just 10.1 feet away. Mars is a tomato, four-tenths of a mile distant at its closest approach to earth. The sun would then be a fireball, 36 feet in diameter, three quarters of a mile away.

So far everything in his tight little model solar system seems within reach, as indeed it may be, someday. Now, in this same scale, where the sun is less than a mile distant, how far away is Alpha Centauri, our nearest star?

Kephart's answer: 47,300 miles away.

Reverting from the model to the real universe, that is 25.3 trillion miles, or 4.3 light-years. A light-year is the distance -- about 6 trillion miles -- that light, moving at 186,000 miles per second, can travel in a year.

But we don't travel at the speed of light. A state-of-the-art unmanned star probe goes 60 miles per second. That is 250 times as fast as a cross-country jet, Kephart notes, but only 0.032 percent of the speed of light. It would reach Alpha Centauri in about 13,000 years.

Kephart's calculations, assuming the best-quality conventional rocket propulsion, show that a one-ton unmanned star probe designed to go 60 miles per second requires about 10 rocket stages. The assemblage would have an initial launch mass equivalent to about 2,000, 100,000-ton Ronald Reagan-class aircraft carriers. And all this for a 13,000-year goal.

Just for fun, he suggests, let's peek into the future and think about alternatives. Based on Einstein's famous insight that matter is energy, E=mc, someday we will capture energy from essentially weightless fuel sufficient to help accelerate a starship maybe to about 10 percent to 25 percent of the speed of light. That is fast enough for a round-trip to Alpha Centauri in less than 100 years.

Of course, all that raw energy alone won't take us anywhere, Kephart says. We have to get a grip on something and push against it to thrust off into deep space. Translating boundless energy into useful thrust, he leaves to propulsion wizards of the next millennium. But here is his trial scheme:

Commandeer an iron asteroid about 10 miles in diameter from the Asteroid Belt. Nudge the asteroid into earth orbit, then terraform it into a wheel-shaped, rotating, habitable self-contained starship -- like the space station in the film "2001, a Space Odyssey." Use the iron for spaceship steel structure, and as the platform to push against -- obeying Newton's third law of motion.

It is likely that a crew of about a thousand would be needed. "The crew would have to reproduce, train and sustain itself in isolation for a hundred years," Kephart explains.

What about the reverse situation -- alien star people visiting earth?

Kephart reminds us that every problem we face going to the stars is true for star dwellers coming the other way. Consequently, he regards such alleged other-worldly phenomena as unidentified flying objects as highly unlikely.

"I can't see technically sophisticated extraterrestrials indulging in silly UFO peekaboo games, suggesting low opinions for us gullible Earth folk," he says. "I go along with scientists who link UFOs to natural earth events, or to willful self-deception, fanciful folklore, mass hysteria, superstition, deliberate fakery and the fun of believing the unbelievable.

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