Lance, R. J. | Search NASA

NASA NTRS1984

Space Shuttle Orbiter improved auxiliary power unit

The Space Shuttle Orbiter Auxiliary Power Unit subsystem has operated successfully on three vehicles by meeting mission requirements and has proven the design for space operation. The current Auxiliary Power Unit (APU) operational life is limited to 12 missions and the APU turnaround between flights is longer than originally anticipated. The Improved APU objective is to increase life to 50 missions, reduce the three - APU subsystem vehicle weight by 140 lbs., and reduce turnaround time. The design changes incorporated into the Improved APU and the associated development testing are described.

Hagemann, D. W.↗

NASA NTRS1984

Ground test challenges in the development of the Space Shuttle orbiter auxiliary power unit

A conventional aircraft hydraulic system design approach was selected to provide fluid power for the Space Shuttle Orbiter. Developing the power unit, known as the Auxiliary Power Unit (APU), to drive the hydraulic pumps presented a major technological challenge. A small, high speed turbine drive unit powered by catalytically decomposed hydrazine and operating in the pulse mode was selected to meet the requirement. Because of limitations of vendor test facilities, significant portions of the development, flight qualification, and postflight anomaly testing of the Orbiter APU were accomplished at the Johnson Space Center (JSC) test facilities. This paper discusses the unique requirements of attitude, gravity forces, pressure profiles, and thermal environments which had to be satisfied by the APU, and presents the unique test facility and simulation techniques employed to meet the ground test requirements. In particular, the development of the zero-g lubrication system, the development of necessary APU thermal control techniques, the accomplishment of integrated systems tests, and the postflight investigation of the APU lube oil cooler behavior are discussed.

Chaffee, N. H.↗