Description: NASA’s goal of safely landing humans on the surface of Mars in the 2030s requires several enabling technologies. One of those technologies is using a cluster of large rocket engines to decelerate cargo and/or crewed entry vehicles (roughly 20 metric tons in mass), starting at supersonic conditions during atmospheric entry, descent, and landing (EDL). The last two phases of EDL, also called the propulsive descent (PD) and landing phase, will allow safe and precise landing at pre-determined locations on Mars. PD replaces a supersonic parachute that has been successfully used for robotic Mars EDL, but which do not scale to larger payloads. PD has only been used by NASA at low subsonic conditions on much smaller robotic science missions, such as Mars Phoenix. There are no existing relevant ground or flight test data sets that can be used to estimate the accuracy of predictive methods for Mars PD performance. One of the highest risks for high-mass Mars EDL is the uncertainty in predicting the spacecraft’s aerodynamic behavior during PD. Several years of consistent ground and flight testing, with analytical model development in parallel, are needed to advance PD aerodynamic modeling for high-mass Mars EDL. The overall goal of the Descent Systems Study (DSS) project is to advance analytical modeling of PD aerodynamics in order to reduce the risks in eventual flight implementation. The Descent Systems Study project partnered with ARMD's Aerosciences Evaluation and Test Capability (AETC) office to compare computational fluid dynamics (CFD) models to supersonic PD aerodynamics in a wind tunnel environment. The AETC's “CFD as a Surrogate for High Speed Supersonic Testing" project is funding a supersonic PD test in the NASA Langley Unitary Plan Wind Tunnel (UPWT) test section 2. The test will be conducted using two models that are representative of low and mid lift-to-drag ratio (L/D) Mars EDL vehicle concepts. The main DSS task is to complete an uncertainty quantification (UQ) of high-fidelity CFD results at UPWT conditions using test data as the reference. UQ of CFD methods for supersonic PD will inform uncertainties for Mars EDL and future investments needed to improve both test techniques and CFD capabilities.

Benefits: Understanding the descent and landing technology needs at Mars impacts how and what we choose to test at the Moon. Current technology can deliver a one metric ton robot to the surface of Mars. Humans will require nearly 80 tons of supplies and infrastructure to live there for an extended time. We are evaluating new technologies capable of delivering much larger masses to the surface (4-20t Landers). This project is coordinated with AETC to conduct wind tunnel propoulsive descent testing and CFD to understand the aerodynamic characteristics of representative PD vehicle configurations, and the uncertainties of CFD methods to predict PD aerodynamics. The DSS project will share major findings and data products with stakeholders in various mission directorates. CFD lessons learned and best practices for calculating propulsive descent aerodynamics will again be updated and shared with STMD, SMD, ARMD, and HEOMD. Specifically, the technical challenges of using CFD design tools to build propulsive descent aerodynamics models will be shared with GCD's Entry System Modeling (ESM) project, where relevant CFD development tasks are taking place. Also, the computer resources required to complete the project's tasks will be tracked and shared with mission directorates that foresee the need for the technology, especially for Mars EDL. Furthermore, recommendations for better methods to test propulsive descent aerodynamics, including ground facilities and flight-testing opportunities, will be shared with the goal of improving data relevance and quality for further technology development efforts.