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Accession Number N20120012825
Title Determination of Barometric Altimeter Errors for the Orion Exploration Flight Test-1 Entry.
Publication Date Aug 2012
Media Count 20p
Personal Author D. L. Brown J. P. Bunoz R. Gay
Abstract The Exploration Flight Test 1 (EFT-1) mission is the unmanned flight test for the upcoming Multi-Purpose Crew Vehicle (MPCV). During entry, the EFT-1 vehicle will trigger several Landing and Recovery System (LRS) events, such as parachute deployment, based on on-board altitude information. The primary altitude source is the filtered navigation solution updated with GPS measurement data. The vehicle also has three barometric altimeters that will be used to measure atmospheric pressure during entry. In the event that GPS data is not available during entry, the altitude derived from the barometric altimeter pressure will be used to trigger chute deployment for the drogues and main parachutes. Therefore it is important to understand the impact of error sources on the pressure measured by the barometric altimeters and on the altitude derived from that pressure. The error sources for the barometric altimeters are not independent, and many error sources result in bias in a specific direction. Therefore conventional error budget methods could not be applied. Instead, high fidelity Monte-Carlo simulation was performed and error bounds were determined based on the results of this analysis. Aerodynamic errors were the largest single contributor to the error budget for the barometric altimeters. The large errors drove a change to the altitude trigger setpoint for FBC jettison deploy.
Keywords Altimeters
Atmospheric entry
Crew exploration vehicle
Flight altitude
Flight tests
Global positioning system
Monte carlo method
Spacecraft landing

Source Agency National Aeronautics and Space Administration
NTIS Subject Category 84G - Unmanned Spacecraft
Corporate Author National Aeronautics and Space Administration, Houston, TX. Lyndon B. Johnson Space Center.
Document Type Conference proceedings
Title Note N/A
NTIS Issue Number 1303
Contract Number N/A

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