posted February 03, 2012
Six Aerospace employees received awards from Lockheed Martin on Jan. 27 expressing recognition for quickly developing an in-situ X-ray method for finding defective spacecraft attitude-control thruster valves — “thereby resolving a critical Program issue.”
Eric Johnson, Paul Adams, Shant Kenderian, Sahar Maghsoudy-Louyeh, Yong Kim, and Robert Pan were cited by Lockheed Martin’s Military Support Programs (MSP) with “sincere gratitude and recognition for the contributions made in resolving the Rocket Engine Module (REM) valve issues.”
“This award recognizes a core Aerospace capability – the talent to solve hard problems and come up with solutions that help the contractors save time and money for our customers,” said Joe Strada, general manager, Electronic Programs Division.
The Aerospace team was called on last year after an attitude-control thruster valve became stuck during an acceptance test and would not expel propellant. If this occurred on a satellite in orbit, it would make it difficult to properly point and position the satellite.
Lockheed Martin determined that the problem was an improperly seated spring in the thruster valve. Engineers from the contractor were able to view the spring in their laboratory with an X-ray CT scanner. However, they were unable to produce clear images of the spring with a portable X-ray machine that could be taken to where the satellites were being built. At this point they requested assistance from The Aerospace Corporation Nondestructive Evaluation Group, which had worked closely with them in the past to solve other difficult inspection problems.
Radiographic examination of the thrusters presented a real inspection challenge as it entailed imaging tiny springs that were buried within a metal housing and surrounded by dense wire coils. Several knowledgeable industry experts consulted by the contractor said it would be very difficult, if not impossible, to produce clear enough images of the springs to tell which valves were defective.
It was indeed difficult, but the Aerospace team eventually came up with a solution. Using a portable micro-focus X-ray machine and a mock REM unit provided by the contractor, the Aerospace team ran tests in the A6 laboratories to determine what combination of beam parameters, film type, and shielding would yield a useful image. They then developed the imaging protocol and image analysis algorithms and worked with the contractor to develop a fixture to accurately position the source near the thrusters on the satellite. Following a demonstration of the technique, at Program request, they moved forward to inspect flight vehicles that were in various stages of being built.
A potential “show-stopper” was encountered early on when the Aerospace portable X-ray source was damaged during shipping to the contractor facility. Units like it generally take several months to repair or procure. Quick work by the team in locating a similar unit available for immediate purchase, and fast action by business manager Debra Smith and procurement administrator Marilyn McCoy in moving this capital purchase through allowed activities to resume with little more than a week delay.
Scores of thrusters were examined using the Aerospace in-situ X-ray technique; of these, two that were found to be defective were removed and replaced. Further examination of the removed thrusters confirmed the results. Because the other thrusters on the vehicles did not have to be removed for inspection, the Aerospace technique resulted in a significant savings in both cost (millions of dollars) and schedule. The technique was also briefed to other space programs that employ the same thruster valve design for possible use on their vehicles in build.