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No one yet knows the precise location of any extinct comet that is easily accessible from Earth. However, scientists have pinpointed the locations of some of the five to ten million near-Earth asteroids that are as large as ten meters across. They're called "carbonaceous chondrites," according to Ostro. "It's this black stuff," he says, a primitive kind of meteorite material composed, in part, of water. Ostro says if you heat a carbonaceous chondrite up to a few hundred degrees centigrade, you liberate the water from the salts and silicates to which it is chemically bound "In the cold of space, the water would condense on anything solid," Ostro explained. Furthermore, as you continue heating the material, it yields other valuable substances. "You get organic chemicals that can be used to make fuel. People have done experiments where they've grown microorganisms and plant-tissue cultures in carbonaceous chondrites. So the stuff has nutrient value; you can think of it as potting Prototype o fhybrid-motor-powered vehicle soil. You have all the resources that you might need in the carbonaceous-chondritic asteroids."

Many of these are within easy reach of the Earth. "Right now," Ostro says, "the most accessible object that we know in the solar system -- with a secure orbit -- is a tiny asteroid probably about the size of a baseball diamond, a spheroidal object named 1998 KY26.1t looks like it's a carbonaceous chondrite." If you take a basketball-size chunk of it and you distill it, ''You can get enough water to keep you alive for a day. Water and oxygen. And it's easy to do,' Ostro says. Think of that basketball-sized chunk as life-support for one person per day, he directs. "KY26 is 100 times the diameter of that ball, so it has a million times the volume, so it's life-support for a million person/days. In other words, it could keep 1000 people alive for 100 days. Or it could keep a couple dozen people alive for their entire lives."

Ostro believes that only when the infrastructure has been created to tap such resources will the chasm between reality and fantasy about space travel be bridged. And he thinks that's destined to happen. Exploration is the inspiration that fuels civilization, he asserts, quoting Bob Dylan: "He not busy being born is busy dying."

Besides its ability to support human life, water in space is "white gold" for another reason, Benson told me. It's made of hydrogen and oxygen. ''And do you know what the main shuttle engines burn when the shuttle takes off? Oxygen and hydrogen!" Benson quotes scientist and writer Robert Heinlein, who 50 years ago said, "When we reach Earth orbit, we're halfway to anywhere." What Heinlein meant, Benson says, was that "the amount of energy to get to Earth orbit is the same as the amount of energy to get anywhere else in the Solar system. The trouble is, when we get to Earth orbit, our tank's empty. We're out of gas." Tapping the water content of the near-Earth asteroids would give humanity the gas stations it needs to go where no human has ever gone before.

Benson claims it won't take fancy technology to transform the water into rocket fuel. "We already know how to make solar furnaces on Earth to heat The $10 million prize will go to the creators of the first private vehicle that flies into suborbital space.

Besides its ability to support human life, water in space is "white gold" for another reason, Benson told me. It's made of hydrogen and oxygen. ''And do you know what the main shuttle engines burn when the shuttle takes off? Oxygen and hydrogen!" Benson quotes scientist and writer Robert Heinlein, who 50 years ago said, "When we reach Earth orbit, we're halfway to anywhere." What Heinlein meant, Benson says, was that "the amount of energy to get to Earth orbit is the same as the amount of energy to get anywhere else in the Solar system. The trouble is, when we get to Earth orbit, our tank's empty. We're out of gas." Tapping the water content of the near-Earth asteroids would give humanity the gas stations it needs to go where no human has ever gone before.

Benson claims it won't take fancy technology to transform the water into rocket fuel. "We already know how to make solar furnaces on Earth to heat things up to thousands of degrees. You take the same little thing that you can build in your garage up to space and focus it on the combustion chamber ofa bag of water. You're going to be ejecting superheated steam at the same velocity as the shuttle main engine burns oxygen and hydrogen. That means you have the same propulsive capability in space with water and a solar lens that you do with billion-dollar motors on the shuttle. When you reduce it down to what's called a 'rocket equation,' it's the same thrust."

Excited by such reflections, Benson began attending space conferences, including one in San Diego in November 1996. That's where he met UCSD professor Jim Arnold, a founding director of the California Space Institute (which is headquartered at UCSD). A few days later, Benson showed up at the institute "and wanted to talk about his ideas;' Arnold recalls. "We had speculated earlier that somebody was going to come along sometime who wanted to run a private space mission. And here was this gentleman who came along sooner than we expected. He was -- and is -- an interesting guy." Benson, in turn, says Arnold told him, "This would make our dreams come true. Everyone wants to do missions the right way: small, inexpensive, and cheap. But we butt our heads against the brick wall of NASA:'Arnold volunteered to put together a group to study the feasibility of a private mission to a near-Earth object. That group eventually included 12 graduate and undergraduate students, a couple of professors, and some space-industry veterans, "San Diego is full of retired and fired space engineers since General Dynamics closed down," Arnold elaborates. ''And most of them prefer doing interesting space things to playing golf, so they're willing to come and share." As for the students, Arnold felt that "even if this turned out to be a pipe dream, the students were going to get a lot of useful experience in trying to do a project of this difficulty and originality."

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