Thrusters precisely guide EO-1 satellite in space first
Posted: February 9, 2002

A new generation of thrusters has been used to precisely guide and point a satellite in space, paving the way for use of this technology on future spacecraft to save weight, fuel and cut power consumption.

Engineers used Pulsed Plasma Thrusters (PPT) onboard NASA's EO-1 satellite as a precision attitude control actuator in space. A single PPT unit with two opposing thrust nozzles controlled the 1166-pound (529 kg) spacecraft's pitch (up and down) axis for 4 hours as it made several orbits of the Earth.

Continued testing of the EO-1 PPT is expected to demonstrate additional attitude control capability and thruster performance characteristics.

NASA's Glenn Research Center, Cleveland, developed the PPT system, and NASA's Goddard Space Flight Center, Greenbelt, Md., managed, designed and implemented the PPT experiment into the EO-1 spacecraft.

"Our initial operations with the PPT have been highly successful and we have reached a significant milestone," said Chuck Zakrzwski, Propulsion Systems Engineer at Goddard. "The thruster and the entire spacecraft performed as expected during the PPT calibration and closed loop attitude control tests."

"The path is now open for PPT use on new missions due to the successes in our flight validation and ongoing PPT development," said Scott Benson, Propulsion Programmatic Manager at Glenn.

The PPT is a unique electromagnetic propulsion system that utilizes solid bars of Teflon as fuel. Pulses of electricity, lasting only one one-thousandth of a second, are fired across the Teflon bar. Each pulse turns a minute amount of the Teflon into an electrically charged gas that is accelerated out of the thruster. Each pulse has approximately the same force as dropping a paper clip into the palm of your hand from about one-half inch away. Because the PPT also uses electromagnetic forces, it is three times more fuel efficient than conventional chemical thrusters.

NASA's EO-1 spacecraft is the first to fly the smaller, lighter and more efficient new generation PPT. Engineers tested the thruster's precision attitude control ability by using the PPT in place of one of the conventional reaction wheels. This is the first time this has ever been done and demonstrates the technology could be used as a precision attitude control actuator as well as a precision orbit adjust thruster.

"Potentially, a set of PPTs could be used to replace reaction wheels and their associated electromagnetic torquers as well as the conventional chemical propulsion for both orbit and attitude control," Zakrzwski said. "An analogy to this would be an automobile that has its power steering and its forward motion supplied by their common power source - the car's engine - rather than separate, multiple power sources."

"Such a configuration would offer better performance and likely be more weight and cost effective than conventional systems," Benson said. "The PPT's extremely small impulse level, high propellant efficiency, low power and compact size make it well suited for a number of precision pointing and precision positioning functions on future spacecraft."

The Pulsed Plasma Thruster Technology Demonstration is the result of a partnership between NASA's Goddard Space Flight and Glenn Research Centers, General Dynamics Space Propulsion Systems and Swales Aerospace. The EO-1 spacecraft is managed by Goddard and was built by Swales Aerospace. The spacecraft is part of the New Millennium Program managed by NASA's Jet Propulsion Laboratory.

More information about the PPT and EO-1 mission can be found at: