NASA Jet Propulsion Laboratory, California Institute of Technology

A soccerball-shaped carbon molecule may be the perfect propellant for a type of spacecraft engine that produces thrust by expelling charged atoms or molecules.

Stephanie D. Leifer, an engineer at NASA's Jet Propulsion Laboratory, and Winston A. Saunders of the California Institute of Technology, propose to use the molecule Carbon 60 as a fuel in ion engines. These engines, which generate thrust by ionizing and accelerating propellants, use less fuel than conventional chemical thrusters.

Leifer believes Carbon 60 has properties that will reduce the energy required to ionize the propellant. "For applications where it is desirable to operate at relatively low to moderate exhaust velocity, ion engines using low ion mass propellants become less efficient," Leifer said.

"A large molecule such as Carbon 60 would allow for more efficient operation at low exhaust velocities," she said.

Because the structure of Carbon 60 resembles a geodesic dome, it also is called "buckminsterfullerene" in honor of the dome's inventor, R. Buckminster Fuller. Scientists informally refer to the molecules as buckyballs.

JPL and Caltech have started a joint effort to examine the use of Carbon 60 in ion thrusters. The program will study basic properties of the molecule important to ion propulsion, and will evaluate it as a fuel in a small ion engine testbed.

The first practical application of ion engines most likely will be in orbital transfer missions and station-keeping for satellites in geosynchronous orbit 22,300 miles above Earth. Later, Carbon 60 could give advanced ion engines much higher thrust and power levels than are possible today.

"This project is an excellent example of looking beyond one's sub-specialty to find new and potentially useful technologies," said Saunders. "Stephanie and I got together over lunch one day to talk about using clusters in ion thrusters. I knew something about Carbon 60, but nothing at all about ion engines. She knew about the current limitations and requirements of ion engines. On the spot we cooked up this idea to use C60 and within 2 weeks we had filed a patent disclosure.

"It's the kind of synergistics Buckminster Fuller advocated," he added.

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