Martin creates satellite on a tether Shuttle to use device for atmospheric tests

November 28, 1991|By Ted Shelsby

Engineers at Martin Marietta Corp. have come up with a novel way for scientists to learn more about a layer in the Earth's upper atmosphere -- tie a satellite on a long "string" and lower it from a space shuttle.

The layer that scientists want to explore -- between 55 miles and 125 miles above the Earth -- is not accessible by high-altitude airplanes, balloons or free-flying satellites.

The system, called the tethered satellite program, was developed by Martin under a $100 million National Aeronautics and Space Administration contract.

"It's not a simple reel with a big motor on it," Raymond J. Head, the engineer responsible for the design of the system that will deploy thesatellites, told Martin's employee magazine. "It's much more complex than that, and it took a lot of technical know-how to accomplish."

Martin's role in the program was to build the deployer that will be carried aboard the shuttle. It includes a 40-foot boom that lifts the satellite clear of the shuttle before deployment. Martin also makes the reel to retrieve the satellite and the "string" -- actually called the "tether."

The tether is about the thickness of a shoestring and is made of a thin filament of plastic called Nomex, strands of copper, a coating of Teflon and layers of super-strong braided Kevlar and more braided Nomex on the outside.

The 1,200-pound satellite will be carried away from the shuttle by impulses from a tiny rocket built into the satellite.

The program is a cooperative effort between NASA and the Italian Space Agency, which is supplying the satellite.

During the first mission, scheduled in September, the shuttle crew will seek to demonstrate that the system works. The satellite is to be deployed 12 miles above the shuttle.

Kerry Masson, a spokeswoman for Martin's aerospace division in Denver, where the tether system was made, said that the first mission will include an electrodynamics test in which the satellite and tether will be used to generate electricity as they cut through the Earth's magnetic field at high speed.

When the second tethered satellite mission is launched in the mid-1990s, the satellite will be lowered 62 miles toward Earth to study the upper atmosphere. The maximum range of the tethered system is 78 miles.

Ms. Masson said a tethered satellite could be deployed with one set of instruments, retrieved and equipped with new instruments, and then deployed again.

The system is expected to be used to search for minerals on Earth and for experiments in artificial gravity.

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