Development of an Earth Smallsat Flight Test to Demonstrate Viability of Mars Aerocapture

During this grant, a proposal-ready mission concept was developed for an Earth-based aerocapture flight demonstration. The baseline concept includes trajectory work, preliminary flight system design, and risk assessment, and showcases relevancy to aerocapture at other planetary bodies. The developed concept combines a secondary payload mission architecture with recent advancements in drag modulation technologies, to reduce the complexity and cost of the flight test. The mission concept of operations involves deployment from a geosynchronous transfer orbit and aerocapture into a low Earth orbit. Single-event-jettison drag modulation is used as a control scheme, in which jettisoning of an attached rigid drag skirt during atmospheric flight provides control authority. Trajectory modeling was used to inform structural, thermal, and sizing requirements for a nominal flight system. Monte Carlo simulations were performed to select a guidance numeric predictor-corrector guidance algorithm. Computational fluid dynamics (CFD) simulations were combined with a 6 degree-of-freedom (6DoF) motion propagation model to help characterize the risks associated with the hypersonic drag skirt jettison event. Analysis of the nominal atmospheric trajectory suggests that the expected peak heat rate during this flight test is approximately 500 W/cm2, and the expected peak deceleration is approximately 3.32 g’s. These values, along with a NASA JPL Team-XC study, were used to develop a ~26kg smallsat flight system featuring an aluminum structure and 4.2 cm of phenolic impregnated carbon ablator (PICA) applied as a thermal protection system (TPS) material. Results from the Monte Carlo simulations indicate that the mission concept is robust to day-of-flight uncertainties, and that spacecraft will be able to capture into its target orbit with an apogee that is within 150 km of the target and a perigee within 6.7 km of the target. This accuracy may be suitable for the purposes of this flight demonstration, although further precision is likely required for future scientific missions. Additional Monte Carlo analyses were performed for a similar mission architecture and spacecraft design at Mars, which demonstrated that the selected control scheme and guidance algorithm can be used to capture into orbit somewhat accurately for other planetary targets. Results from the combined CFD / 6DoF separation modeling indicate that the flight system and the drag skirt are not at risk of near- or far-field recontact following the drag modulation jettison event, for a range of potential flight conditions. The results from this investigation have been used to support a 2 year NASA JPL Research & Technology Development Study (R&TD) on a smallsat aerocapture mission to Venus. The mission concept for this Venus R&TD leverages a similar architecture to the Earth flight test developed during this grant.