Rainer Dressler (Air Force Research Laboratory), Benjamin D. Hester (Air Force Research Laboratory), Paul F. Sydney (Boeing Corp.), Lewis Roberts (Boeing Corp.), Kris Hamada (Pacific Defense Solutions), Paul Kervin (Air Force Research Laboratory), Mark P. Bolden (Air Force Research Laboratory), Capt. Albert F. Meza (DoD Space Test Program, Johnson Space Center), Darrin T. Walker (DoD Space Test Program, Johnson Space Center), James C. McLeroy (DoD Space Test Program, Johnson Space Center), Lawrence S. Bernstein (Spectral Science, Inc.), James W. Duff (Spectral Science, Inc.), Matthew Braunstein Spectral Science, Inc.)
Keywords: NROC, Non-resolved Object Characterization
Abstract:
The objective of MAUI (Maui Analysis of Upper Atmospheric Injections) is to measure the spatial and spectral properties of Shuttle engine exhaust interactions with the low-Earth orbit environment and to validate the chemical kinetics and transport physics implemented in a direct simulation Monte Carlo (DSMC) computer model, SOCRATES-P. The code is a research tool that can be applied towards the development of a future maneuver characterization capability. MAUI was manifested during the past 4 Space Shuttle missions. STS-115 resulted in a unique MSSS observation opportunity at conditions where the orbiter was in sunlight while the optical station was in darkness (terminator pass). The crew was ready to conduct a series of burns per MAUI request. The experiment was scrubbed due to concern related to an unidentified object in the vicinity of the orbiter. Instead, MSSS was tasked to image the tail section of the orbiter to ensure the object was not the parachute door. STS-115 passed over MSSS in an attitude in which the Shuttle axis was locked to the MSSS line-of-sight. This required a large number of attitude maneuvers. Unfortunately, the optical station had to reconfigure its telescopes on very short notice, and the fact that the new mission represented an interesting burn observation opportunity, did not register with the ground crew, so only unfiltered images were taken. Nevertheless, the 0.33 deg field-of-view LAAT acquisition scope of the 3.6 m adaptive optic tracking telescope, AEOS, provided extremely interesting unfiltered imagery. A total of 22 attitude control pulsed firings were recorded at very good lighting conditions. Each firing involved 2 or 3 PRCS engines firing bursts between 80 and 320 ms long. In every case, the thrust axis was perpendicular to the line of sight, providing a unique and optimal viewing geometry. By far the most interesting white-light features were transients observed at engine start up and shut-down. These transients are due to droplets, or frozen particles, of un-burnt propellant or condensed exhaust that effectively scatter sunlight. The imagery is such that the velocity of the transients can be accurately determined, thereby providing an excellent opportunity to validate state-of-the-art two-phase flow models implemented in SOCRATES-P. An analysis of the transient speeds based on known PRCS engine start-up and shutdown information will be presented.
Date of Conference: September 12-15, 2007
Track: Non-resolved Object Characterization