Reentry Air Data System for a Sub-orbital Spacecraft Based on X-34 Design

摘要

A design a Flush Airdata Sensing System based on the X-34 configuration is presented. The X-34 was chosen for this study because it incorporates many of the features needed by a commercial suborbital tourist spaceflight system. The X-34 aerodynamic database was developed using public dollars and is available in the public domain. The X-34 FADS uses a matrix of pressure orifices on the vehicle nose to estimate airdata parameters. System details including nosecap design, pressure port locations, processing algorithms, and wind tunnel calibrations are presented. Redundancy management methods are described. For this design study a typical X-34 trajectory was used to generate simulated nosecap surface pressure values based on wind-tunnel derived calibration models. These pressures were corrupted with various noise models and processed by the FADS solver algorithm to obtain airdata estimates. Residuals are used to analyze system performance. The noise models are described in detail. Characteristics of the airdata system in the presence of various error sources are presented evaluated. The operational range of the system is extended to very high altitudes by using a complementary filter to blend inertially derived airdata with the sensed FADS pressure data. Details and sample results from the complementary algorithm are presented.