Experimental Investigations of Fluid-to-Vehicle Interactions during a Reusable Launcher’s Touchdown Impact

Several programmes are dedicated worldwide to the development of reusable vertical take-off vertical landing (VTVL) launch vehicles. Thereby, the touchdown event with its associated impact forces and shocks poses load cases to the vehicle being new in the launcher domain. Furthermore, the application of related knowledge from planetary, exploration-type landers has to be taken cautiously due to the differences between those types of vehicle, particularly with regard to their tank configuration and structural sizing. Depending on flight test conditions and operational concept, non-neglectable amounts of liquid propellant can still be inside the tanks at landing and interact with the vehicle. These interactions cause dynamic and structural effects that affect the landing stability and structural integrity of the vehicle. This study aims to experimentally investigate the fluid-vehicle interactions of a fully functional touchdown demonstrator during touchdown. For this, a vehicle landing engineering model is equipped with a circular cylindrical tank and a series of touchdown test with varying horizontal landing velocities and fill levels is conducted. Thereby, the main objectives are to prove repeatable landing behaviour under sloshing impact for constant landing conditions, characterise the fluid impact on landing stability and investigate the fluid-structure interactions on the tank. Therefor test data of different test cases is compared and analysed with regards to dynamic behaviour and structural responses.