Design and Calibration of the X-33 Flush Airdata Sensing (FADS) System. Meeting Paper AIAA-1998-0201, Research Engineering, NASA Dryden Flight Research Center

Whitmore, Stephen A. and Cobleigh, Brent R. and Haering Jr., Edward A. (1998) Design and Calibration of the X-33 Flush Airdata Sensing (FADS) System. Meeting Paper AIAA-1998-0201, Research Engineering, NASA Dryden Flight Research Center.

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Abstract

This paper presents the design of the X-33 Flush Airdata Sensing (FADS) system. The X-33 FADS uses a matrix of pressure orifices on the vehicle nose to estimate airdata parameters. The system is designed with dual-redundant measurement hardware, which produces two independent measurement paths. Airdata parameters that correspond to the measurement path with the minimum fit error are selected as the output values. This method enables a single sensor failure to occur with minimal degrading of the system performance. The paper shows the X-33 FADS architecture, derives the estimating algorithms, and demonstrates a mathematical analysis of the FADS system stability. Preliminary aerodynamic calibrations are also presented here. The calibration parameters, the position error coefficient (epsilon) and flow correction terms for the angle of attack (Delta alpha), and angle of sideslip (Delta beta) are derived from wind tunnel data. Statistical accuracy of the calibration is evaluated by comparing the wind tunnel reference conditions to the airdata parameters estimated. This comparison is accomplished by applying the calibrated FADS algorithm to the sensed wind tunnel pressures. When the resulting accuracy estimates are compared to accuracy requirements for the X-33 airdata, the FADS system meets these requirements.

EPrint Type:	Other
Keywords:	FADS calibration, Flush airdata sensing (FADS), X-33 vehicle, Redundancy management, Reusable Launch Vehicle (RLV)
Subjects:	Aircraft/Project: X-33
ID Code:	1288
Deposited On:	07 Febuary 2007
Additional Information:	32 pages. AIAA 36th Aerospace Sciences Meeting and Exhibit, Reno, Nevada, January 12-15, 1998.