Volume 8, Number 5     September/October 2000

Company Delivers Rockets and SBIR Success

Space rockets made of rhenium promise to last longer, and may have greater payload capacity to orbit due to increased efficiency. Rhenium, though, is one of Earth’s rarest metals. It is also hard to obtain, hard to work and hard to form.

But Rhenium Alloys, Inc., of Elyria, Ohio, has delivered two small chemical rocket thrusters made of rhenium to NASA Glenn Research Center in Cleveland, Ohio. The delivery completes the second and final phase of the company's SBIR contract with Glenn and sets the stage for further improvements in the life and capabilities of rockets for both commercial satellites and NASA space exploration missions.

	Rhenium Alloys, Inc. delivered a small satellite thruster made of rhenium to NASA Glenn Research Center. The thruster was designed by Primex Space Systems. (Photo provided by NASA Glenn Research Center.)

The thrusters are the product of new manufacturing processes that reduce both manufacturing time and cost, while improving product quality. Room temperature isostatic pressing (applying pressure evenly to all sides of the item) was used to compact rhenium powder into the near final shape and dimensions of the thruster. Containerless hot isostatic pressing was used to consolidate the powder until its molecules aligned into the strongly bonded crystalline structure of conventionally cast metals.

“We would never have been able to develop these processes without the financial and technical support of the SBIR contracts,” said Todd Leonhardt, chief metallurgist at Rhenium Alloys, Inc. “The advice and encouragement we received from Glenn researchers was also invaluable.”

During the late 1980s, Glenn researchers began looking for ways to reduce the costs of deep space missions by making rockets last longer and use less fuel. Rhenium, with its very high melting point of 3180¡ Celsius and durability after repeated temperature swings, seemed to fit. A rocket made of rhenium could be cooled simply by radiating its heat into space instead of being cooled by a fuel film layer against the thruster walls, a major source of combustion inefficiency.

The problem was not just with rhenium’s scarcity and high cost, but also with the high cost and difficulty of making it into useable parts. Glenn researchers found several less costly forming methods, but believed the manufacturing community was best suited to perfect those methods and put them into practice.

“Meeting NASA’s future mission needs by putting together NASA researchers and small businesses inter-ested in conducting research is our primary task,” said Walter Kim, SBIR program manager. “In this case, we also contacted the two rocket manufacturers for help in evaluating both the manufacturing process and the thrusters.”

The rocket manufacturers, TRW’s Space and Technology Division of Redondo Beach, California, and Primex Space Systems (formerly Kaiser Marquardt) of Van Nuys, California, provided their designs for making the thrusters. After the finished thrusters are coated with an oxidation-resistant coating of iridium, TRW and Primex will test their respective thruster in their own facilities.
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