Purdue University and Lockheed Develop Technique to Save Aging Satellites

Electronic systems in geosynchronous orbit satellites have become more reliable.
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Electronic systems in geosynchronous orbit satellites have become more reliable. As a result a satellite’s usable life is likely to be determined by the amount of fuel available to maintain its orbital position.

Until recently, many satellites used multiple fuel tanks to feed the thrusters used to maintain its location. The fuel was pushed out of the tanks with helium gas. Unfortunately, when one fuel tank used up all its fuel, the helium gas from the empty tank prevented the fuel from the other tanks from igniting properly, making it impossible to control the satellite.

As a result, if one tank was low on fuel, even if the other tanks had more fuel, it was necessary to move the satellite out of the geosynchronous orbit to a location where it wouldn’t cause damage to other satellites.

Researchers at Purdue University, working with scientists from Lockheed Martin, developed a method for moving fuel from one tank to another on the satellite, thus extending its life, the university announced. Purdue did not identify the two satellites involved, but said the technique provided an extra six months of useful life.

Balancing fuel between the tanks in the satellites took a year-and-a-half. Measuring the amount of fuel in a tank on a satellite isn’t easy—conventional floats won’t work because there is no gravity. Thermal gauging was used to determine the amount of fuel in each tank. The news release uses an analogy of a pot on a stove to show how this works. A pot with little water will heat up faster than one with more water.

“We were really excited to see that we could take our new propellant-gauging method to provide this lifetime maximization in satellites that were never designed to have anything like this done to them,” said project manager, Dr. Boris Yendler, a senior thermal system analyst at Lockheed Martin Mission Services in Sunnyvale, Calif.

Steven Collicott, a Purdue professor of aeronautics and astronautics, said the problem’s complexity is illustrated by the level of skills needed—most researchers involved in the work have doctoral degrees in aerospace engineering.