Process control: Even rockets need regulation strategies

It only has to run for 8.5 minutes, but during that time the control system has to keep the space shuttle Endeavour’s booster rockets running properly to keep it flying true. The shuttle is equipped with three Pratt & Whitney Rocketdyne main engines that use advanced health management system (AHMS) controllers to monitor overall performance during the short but critical firing period. The AHMS controllers monitor engine vibration and have the ability to detect real versus false signals. During the August 8 launch, for the first time, all three of the controllers were active and could have prompted actions in the engine systems if unacceptable vibration levels were detected during the firing of the engines.

The AHMS controller improves flight safety by offering near-instant and automatic response to potential problems in the event they occur. “This is a major upgrade for the engines,” says Jim Paulsen, Pratt & Whitney Rocketdyne space shuttle program manager, “and we’re excited to finally put the new AHMS into action after years of hard work from a dedicated team of NASA, Pratt & Whitney, and Honeywell personnel. Once again, the team has succeeded in introducing advancements that further enhance flight safety.”

The AHMS controller was developed in conjunction with NASA’s Marshall Space Flight Center and Honeywell International . Its enhancements are expected to improve flight safety by 23%, with real-time automatic response to potential issues. Endevco Corporation , a leader in sensing solutions for demanding vibration, shock and pressure applications, provided the advanced accelerometers for the engine controllers using 7704 series isoshear piezoelectric accelerometers.

Pratt & Whitney Rocketdyne’s space shuttle main engine is the world’s only re-usable high performance liquid-fuel rocket engine. August’s successful launch brings the fleet total to 357 engine flights and nearly 183,000 seconds of flight operation. Upon return of Endeavour, the engines will be removed from the orbiter and prepared for future missions.

—Edited by Peter Welander, process industries editor, PWelander@cfemedia.com ,
Control Engineering Weekly News

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