Experimental Investigation of Plume-Induced Flow Separation on the National Launch System 1 1/2-Stage Launch Vehicle

摘要

An experimental investigation of plume-induced flow separation on the National Launch System (NLS) 1 1/2-stage launch vehicle was done. This investigation resulted from concerns raised about the flow separation that was encountered on the Saturn 5. A large similarity exists between configurations and nominal trajectories. The study involved the use of solid plume simulators to simulate the base pressure encountered by the vehicle due to engine exhaust plumes at predetermined critical Mach numbers based on Saturn 5 flight plume effects. The solid plume was varied in location, resulting in a parametric study of base pressure effects on flow separation. In addition to the parametric study of arbitrary plume locations, the base pressure resulting from the nominal trajectory was tested. This analysis was accomplished through two wind tunnel tests run at NASA Marshall Space Flight Center's 14 x 14-inch Trisonic Wind Tunnel during 1992. The two tests were a static stability and a pressure test each using a 0.004-scale NLS 1 1/2-stage model. This study verified that flow separation is present at Mach 2.74 and 3.48 for predicted flight base pressures at nominal or higher levels. The flow separation at the predicted base pressure is only minor and should not be of great concern. It is not of the magnitude of the flow separation that was experienced on the Saturn 5. If the base pressure exceeds these nominal conditions, the flow separation can drastically increase, and is of concern.