Determination of reentry parameters during descent from low earth orbit

This research attempted to develop a useful, interactive computer program to predict the reentry parameters on a vehicle as it descends to Earth from low earth orbit. Beginning with a spacecraft in stable orbit, it determines the burn necessary to embark upon the desired trajectory through the atmosphere. The reentry path is initially described by the altitude, velocity and flight path angle. A numerical integration routine is performed to step down through the altitude levels, recomputing new values each step. The g loading is also determined at each altitude. To validate the program US Space Shuttle flight STS-4 flight data were analyzed and compared to predictions from the program. The software had to account for a lifting body, gravity gradients, and flight vehicle roll angles. The Earth was treated as a non-rotating sphere, and the shuttle a point mass. The program predicted the flight velocity of the shuttle well. Limitations of the program occur as the vehicle skips, as it tries to maintain level flight, and as the velocity slows too much. At shallow reentry angles the parameters were found to be very sensitive to small changes.