Abort Motor Research Articles

Heated Helium to Simulate Surface Pressure Fluctuations Created by Rocket Motor Plumes

The solid-rocket plumes from the abort motor of the multipurpose crew vehicle were simulated using hot, high-pressure, helium gas to determine pressure fluctuations on the vehicle surface in the event of an abort. About 80 different abort situations over a Mach number range of 0.3 to 1.2, and vehicle attitudes of , were simulated using a 6% scaled model inside the NASA Ames Transonic Wind Tunnel. The test showed very high level of surface pressure fluctuations caused by the hydrodynamic near-field of the plume shear layer. The plumes grew in size with increasing flight Mach number, which was associated with a lowering of the ambient pressure. This caused an increase of plume impingement on the vehicle. Interestingly, the trend was a decrease in the level of pressure fluctuations with increasing impingement. The wind-tunnel data were compared against flight data from the Pad Abort 1 flight test. Despite various differences between the transient-flight situation and the steady-state wind-tunnel simulations, the hot-helium data were found to replicate Pad Abort 1 fairly reasonably. The data gathered from this one-of-a-kind wind-tunnel test fills a gap in the manned-space programs, and will be used to establish the acoustic environment for vibro-acoustic qualification of the multipurpose crew vehicle.

Launch pad abort of the HL-20 lifting body

The capability of the HL-20 lifting-body spacecraft to perform an abort maneuver from the launch pad to a horizontal landing was studied. This study involved both piloted and batch simulation models of the vehicle. A point-mass model of the vehicle was used for trajectory optimization studies. The piloted simulation was performed in a fixed-base simulator. A candidate maneuver was developed and refined for the worst-case launch-pad-tolanding-site geometry using an iterative procedure of off-line maneuver analysis followed by piloted evaluations and heuristic improvements to the candidate maneuver. The resulting maneuver demonstrates the launch site abort capability of the HL-20 and dictates requirements for nominal abort motor performance. The sensitivity of the maneuver to variations in several design parameters was documented.