NASA no longer has the kind of cash it did in the Apollo days, but the impulse to explore is as strong as ever. It just needs to be done on a leaner budget. In response to the agency's austerity program, a group of scientists has gone the distance with an ultraefficient replacement for chemical rockets. Solar electric ion propulsion, first developed by NASA visionary Harold Kaufman in the 1960s, has now proven itself capable of propelling a probe through the solar system, promising an era of faster and more economical space exploration.
Deep Space 1, launched last October, is using an ion drive to visit an asteroid and two comets. Though Deep Space 1 is primarily a technology test bed for future missions, it will gather data as it goes. The probe was produced by the NASA Solar Electric Propulsion Technology Application Readiness program, whose manager, John Stocky, is clear about his goal: "If we want to fly spacecraft, we have to make them cheaper."
Ion propulsion will be a big help. Its high efficiency—ten times greater than chemical propellants—dramatically cuts down on the amount of material a craft has to haul along. The ion engine is compact, just under a foot in diameter. It gently pushes the spacecraft forward by firing ions, or electrically charged atoms, out into space. Cathodes spew electrons into a chamber filled with xenon gas. The electrons smash into the xenon atoms, knocking away an electron and turning the atoms into positively charged ions. A pair of charged metal grids pulls the xenon ions out the back of the engine at more than 60,000 miles per hour, which drives the spacecraft forward.
Because of power limitations, the resulting thrust is feeble, equivalent to only one-fiftieth of a pound—comparable to the heft of a sheet of paper and about 10,000 times weaker than traditional propulsion systems. What the ion engine lacks in immediate gratification, however, it more than makes up for in persistence. Gradually, the spacecraft reaches high speeds, with remarkably little wasted energy.
"As far as the Jet Propulsion Laboratory and NASA are concerned, this technology is no longer experimental," says Stocky. "It's part of the normal arsenal of things we have with which to execute deep- space missions."
FINALISTS
To the Moon, Cheaply INNOVATOR: Alan Binder, Lunar Research Institute
Lunar Prospector rocked the Earth last winter when it found evidence of ice at the moon's poles. Binder's privately funded design for the craft used off-the- shelf hardware and focused on one clear goal: mapping lunar resources. Lockheed Martin engineers completed the project in conjunction with NASA Ames Research Center for a bargain $63 million.
Binder believes fully commercial space missions are coming soon. "The only way we're going to study the solar system is to do it as a business," he says.
Flying Robot INNOVATORS: Tad McGeer, The Insitu Group; Greg Holland, the Australian Bureau of Meteorology
What's the weather like in the middle of the ocean? Meteorologists would love to know. Real-time measurements over remote, midocean locations could allow substantially improved forecasts. Back in 1991, Tad McGeer, president of the Insitu Group in Bingen, Washington, envisioned an intelligent automated aircraft to do the job. The plane, Aerosonde, would navigate without human input and orient itself using the global positioning satellite system.
McGeer worked out the technical details, and Greg Holland raised the funding that made the project possible. Aerosonde crossed the Atlantic last summer—the first unmanned craft to manage the feat.
