Analysis and Optimization of Thermal Protection System Design for a Manned Martian Entry Vehicle
HP390 Andrew Bingham 04/05/06
Introduction On January 14th, 2004, President George W. Bush gave a historic speech at the headquarters of the National Aeronautics and Space Administration in Washington, D.C. President Bush unveiled a new Vision for Space Exploration, and in doing so gave NASA its first clear direction for future exploration beyond Low Earth Orbit since the Apollo lunar program ended in 1974. The Vision directs NASA to finish the International Space Station and retire the Space Shuttle by 2010, and to begin developing the new spacecraft required to enable further human exploration of the Moon and eventually Mars. Central to achieving the goals of the Vision is the new manned spacecraft, which is currently referred to as the Crew Exploration Vehicle (CEV). The CEV reference design currently consists of a five meter diameter blunt capsule with a shape similar to that of the Apollo capsule. Crew capacity is expected to be four astronauts for missions to the International Space Station and the Moon, and six for potential future missions to Mars. The CEV will be launched on a Crew Launch Vehicle derived from the Shuttle Solid Rocket Booster and the J-2S engine from the Apollo program. The current CEV is being designed as a base upon which future improvements can be made to enable longer durations missions to destinations beyond the Earth-Moon system, including Mars and possible the Asteroid Belt. While the CEV is designed specifically to carry astronauts into space and return them to Earth’s surface, a vehicle will eventually be required which is able to safely deliver a crew to the surface on Mars. This Mars Entry Vehicle (MEV) will undoubtedly draw heavily on the technology developed as part of the CEV program. Previous missions to re-enter the Martian atmosphere have included the Viking 1 & 2 Landers, Mars Polar Lander, Mars Pathfinder, and the twin Mars Exploration Rovers. All of these missions have utilized ablative heat shields designed based on the best current knowledge of the Martian atmosphere. These unmanned missions, while successful, were not necessarily held to the same safety standards as a manned MEV. Thermal protection is critical to maintaining the safety of the crew and the integrity of the vehicle during a re-entry mission. Even when a Thermal Protection System operates properly, thermal loading can cause changes in the way that a
spacecraft’s structure responds to the atmospheric forces which are also generated during re-entry. The objective of this thesis is to investigate potential thermal protection system designs for a manned Mars Entry Vehicle, taking into account the entire range of thermal protection systems which are currently available and those may be available when manned exploration of Mars begins in the 2030 timeframe. Methods This project will make use of several NASA resources, as well as knowledge gained from heat transfer, aerodynamics, gas dynamics, and structures classes at Clarkson University. Analysis of TPS performance will be conducted with increasing levels of accuracy, culminating in an analysis of the aerothermal effect on the spacecraft structure during re-entry. A representative ‘best’ design for the MEV TPS will be identified based on the overall results. Based on the mass of previous manned and unmanned spacecraft design and the geometry of the Fast Opposition trajectory which current Mars Reference Missions make use of, the entry mass, velocity, and trajectory of the MEV will be estimated. These parameters will be combined with a Mars Atmospheric Model from NASA Glenn to provide information on atmospheric heating of the MAV during atmospheric entry. One-dimensional analysis of TPS performance for specific TPS configurations will be performed using techniques outlined in Heat and Mass Transfer, 5th Ed. Twodimensional analysis of the blunt body in the atmospheric flow will be conducted using a program such as MARC or ANSYS, combined with the Mars Atmospheric Model. Based on these analyses, an optimum TPS configuration will be selected for implementation on the 3-D model of the MEV. A 3-D model of the MEV will be generated, with sufficient fidelity for atmospheric and structural calculations. Available NASA hypersonic re-entry codes will
be used to perform aerodynamic analysis of the entry profile. Once the thermal loading of the structure is known, this information will be used to determine aerothermal effects on the structure of the vehicle and its performance. Wherever possible, results will be compared to results for previous unmanned Mars entry vehicles, as well as other blunt body capsules such as the Apollo capsule. Work will be coordinated with applicable NASA centers where possible to ensure that a measurable contribution is being made to the engineering community’s understanding of entering the Martian atmosphere.
Plan The research outlined above will be performed on the following timeline: Spring 2006 – Continue Background Research Spring 2006 – Request NASA Mars Atmospheric Model Early Summer 2006 – Select Representative TPS Systems Early Summer 2006 - Perform 1-D Thermal Analysis Late Summer 2006 – Perform 2-D Thermal Analysis Late Summer 2006 – Develop 3D MEV Model Fall 2006– Perform 3-D Thermal Analysis Fall 2006 – Perform Analysis of Aerothermal Structural Effects This will allow for completion of the project and presentation of a paper at the AIAA Region I-Northeast Student Conference at the Massachusetts Institute of Technology in March of 2007, as well as completion of the Honors Thesis requirements well before the end of the Spring 2007 semester.