Feasibility of DLR’s STG-ET vacuum chamber for simulation of the VLEO environment

Abstract

Within recent years, the very low earth orbit (VLEO) has seen a massive gain in interest for future long term satellite missions, especially within the field of earth observation and communications. Development of systems for such missions can be challenging, since the residual atmosphere in the desired orbits significantly changes mission requirements. While the existence of a residual atmosphere enables new mission concepts such as air-breathing electric propulsion (ABEP) and aerodynamic maneuvers using satellite surfaces, it also means that satellite systems are exposed to higher grades of erosion due to interaction with the residual molecules, especially atomic oxygen. Therefore, the qualification of such systems becomes increasingly important. This work shall represent the operational capabilities of DLR’s “Simulationsanlage für Treibstrahlen Göttingen – Elektrische Triebwerke” (STG-ET, Simulation Facility for Thrusters Göttingen – Electric Propulsion) facility with respect to the simulation of the VLEO environment. The large volume of the facility gives the possibility to test complete (sub-) systems such as thrusters or satellite components under high vacuum conditions, due to the capabilities of the vacuum pumping system, consisting of multipleturbo- and cryopumps. The operational experience and parameters of such a large-scale research facility as well as concepts for the simulation of the VLEO environment will be discussed. A possible experiment could be the integration of an ion source within the facility to simulate the atmospheric flow conditions present in the VLEO environment, resembling a rarefied gas wind tunnel, similar to experiments on the interaction of satellite surfaces with hypersonic rarefied gas flows conducted at DLR Göttingen in the 1970s, which will also be presented briefly. Such an experimental setup would allow to research the interaction of highly rarefied, ionized gas flows with satellite components and structures. The pumping capabilities of the facility allow the testing of electric propulsion, which has been its main purpose so far but also becomes interesting within the context of ABEP. A special focus shall be put on the possibility to conduct long-term test campaigns within the scope of weeks or months within the facility, which has been proven successfully within previous experimental campaigns for the industry. Therefore, the qualification of systems for the VLEO environment seems feasible within the STG-ET facility. Further activities and facilities at the DLR Göttingen related to electric propulsion and rarefied gas flows will be discussed.