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July 23, 2004

Kelly Humphries
Johnson Space Center, Houston

Release: #J04-032


NASA engineers at the White Sands Test Facility near Las Cruces, N.M., are celebrating the success of a critical, 96-minute firing that put Cassini into orbit around Saturn after their tests helped qualify Cassini’s main engine. Cassini is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency to study the planet Saturn and its moons, particularly the giant moon Titan. The Cassini spacecraft was launched in 1997 and entered orbit around Saturn, the second-largest planet in the solar system, on June 30, 2004.

White Sands Test Facility performed the development and qualification testing of Cassini’s orbit insertion rocket engines. While most rocket engines are required to fire for only a few seconds or minutes at most, the small 100-pound-thrust main rocket engine aboard Cassini had to fire continuously for more than 5,400 seconds (1 1/2 hours) to slow the vehicle to approximately 17,400 mph to enable Saturn's gravitational attraction to pull it into orbit. If not for that engine firing, the gravity of the gas giant would have flung the small spacecraft onto a trajectory that would have taken it out of the solar system.

“At White Sands Test Facility, we are elated by the success of the Cassini Project, especially the apparently flawless performance of the main engine assembly. Our experience during the qualification of that part of the Cassini spacecraft validates the importance of testing not only manned space vehicles but also unmanned robotic spacecraft,” said Pleddie Baker, who was Chief of the NASA Propulsion Test Office during the testing.

The tests at White Sands Test Facility initially found a design flaw (low-frequency feed-system-coupled combustion instability) that could have caused the engine to fail in flight and ruin the mission, but the system was subsequently redesigned, and the revised propulsion system successfully operated for 200 minutes, demonstrating a nearly twofold margin of safety for performing this critical maneuver nearly seven years after launch.

White Sands Test Facility performed the qualification tests of the Main Engine Assembly in 1995-96 under contract to Martin Marietta Technologies, Inc., now Lockheed Martin Corp. Martin Marietta built the Propulsion Module Subsystem for the Cassini spacecraft under contract to NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

"As the NASA/WSTF Project Manager for the Cassini main engine qualification testing, seeing the successful Saturn orbit insertion burn nearly eight years after our portion of the work was completed was such a great feeling it is indescribable," said Robert Cort, WSTF Cassini Project Manager. “The engine will continue to be used during the orbit phase of the mission, but its big task is done, and I'm proud to have been part of the qualification team.”


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