Space Launch vehicle aerodynamics with hot plumes

Abstract

The aerodynamics around space launch vehicles determine the external forces that these vehicles experience. Hence, the accurate prediction of these loads is crucial for the structural design. Additionally, a better understanding of the fundamental physical phenomena responsible for the observed flow features helps to design the vehicle such that the experienced loads are reduced. Both the better understanding of the loads and the ability to reduce these loads allow for vehicles to be designed more efficiently and carry more payload mass into orbit. Of particular interest for the aerodynamic research is the region at the bottom of the vehicle, displayed in Fig. 1, where a sudden change in diameter at the end of the main body can lead to high mechanical loads. This aspect of space launch vehicles is investigated in branch B of the SFB Transregio 40 [1], funded by the German Research Foundation DFG. Due to its simpler handling both numerically and experimentally, nearly all previous investigations in the literature have investigated the associated phenomena without a propulsive plume or with one resulting from expanding air. Consequently the plume properties differ significantly from those of realistic rocket plumes. Sub­project B5 of Transregio 40, which is handled by the Spacecraft Department of the Institute of Aerodynamics and Flow Technology at the German Aerospace Center DLR, is concerned in particular with the effects that the presence of hot propulsive plumes has on the wake flow field phenomena [2]. For this purpose computational fluid dynamics (CFD) is applied to simulate the flow around a scale­model generic space launch vehicle geometry. The advantage of CFD is the ability to analyze all regions and aspects of the flow field as required with a high level of detail. To ensure the numerical algorithm accurately predicts the real flow physics the results obtained are compared to experimental investigations of key quantities such as wall pressure measurements. In the scope of the project pr62po at LRZ, a sensitivity study based on a configuration with available comparison data in the literature was conducted first. Subsequently, it was investigated which impact changing the plume conditions and wall temperatures has on the flow field and associated vehicle loads.