Rapid Alignment Prototype (RAP) Flight Test Demonstration

Chris Rabourn, William R. Graham and Kevin J. Shortelle

Abstract:	This paper presents the results of an effort directed at developing and flight-testing an innovative rapid transfer alignment algorithm for inertially-guided air-launched munitions. The algorithm, referred to as RAP (Rapid Alignment Prototype), employs a 17-state Kalman filter designed to accurately align a weapon-grade Inertial Measurement Unit (IMU) relative to an aircraft-grade Inertial Navigation System (INS) within five seconds. The alignment procedure requires the pilot to execute only a brief wing-rock maneuver. No time consuming heading changes or lengthy S-turns are required. The RAP Kalman filter achieves the rapid convergence time by recursively processing both velocity-match and attitude-matchmeasurements at a 12.5 Hz rate to estimate and correct IMU velocity, attitude, and inertial sensor errors. Following laboratory and van testing at Eglin AFB, a series of F-16 flight tests were conducted. Flight test results demonstrated that the RAP filter achieved sub-milliradian alignment accuracy in less than 10 seconds. As further confirmation of alignment accuracy, IMU position error statistics were computed over a l00-set post-alignment captive trajectory. Test results indicated that the mean radial position error after l00-set of unaided navigation was roughly 70 ft with an associated CEP of 61 ft. RAP's unprecedented alignment accuracy and reduced launch timeline provide a rapid-response capability for time-critical targets such as mobile launchers and troop emplacements.
Published in:	Proceedings of the 1998 National Technical Meeting of The Institute of Navigation January 21 - 23, 1998 Westin Long Beach Hotel Long Beach, CA
Pages:	557 - 568
Cite this article:	Rabourn, Chris, Graham, William R., Shortelle, Kevin J., "Rapid Alignment Prototype (RAP) Flight Test Demonstration," Proceedings of the 1998 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 1998, pp. 557-568.
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