Entry, Descent, and Landing for Human Mars Missions

GLEX%2012.08.2.6x12677. ENTRY, DESCENT, AND LANDING FOR HUMAN MARS MISSIONS Michelle M. Munk NASA Langley Research Center, USA, Michelle.M.Munk@nasa.gov Alicia D. Cianciolo NASA Langley Research Center, USA, Alicia.M.DwyerCianciolo@nasa.gov One of the most challenging aspects of a human mission to Mars is landing safely on the Martian surface. Mars has such low atmospheric density that decelerating large masses (tens of metric tons) requires methods that have not yet been demonstrated, and are not yet planned in future Mars missions. To identify the most promising options for Mars entry, descent, and landing, and to plan development of the needed technologies, NASA’s Human Architecture Team (HAT) has refined candidate methods for emplacing needed elements of the human Mars exploration architecture (such as ascent vehicles and habitats) on the Mars surface. This paper explains the detailed, optimized simulations that have been developed to define the mass needed at Mars arrival to accomplish the entry, descent, and landing functions. Based on previous work, technology options for hypersonic deceleration include rigid, mid-L/D (lift-to-drag ratio) aeroshells, and inflatable aerodynamic decelerators (IADs). The hypersonic IADs, or HIADs, are about 20% less massive than the rigid vehicles, but both have their technology development challenges. For the supersonic regime, supersonic retropropulsion (SRP) is an attractive option, since a propulsive stage must be carried for terminal descent and can be ignited at higher speeds. The use of SRP eliminates the need for an additional deceleration system, but SRP is at a low Technology Readiness Level (TRL) in that the interacting plumes are not well-characterized, and their effect on vehicle stability has not been studied, to date. These architecture-level assessments have been used to define the key performance parameters and a technology development strategy for achieving the challenging mission of landing large payloads on Mars. I. INTRODUCTION The very low density of Mars’ atmosphere is a major challenge to decelerating spacecraft and landing them safely on the planet. Current technology, utilized to land up to 1 metric ton (mt) vehicles on Mars, is derived from 1960’s and 1970’s Viking era technology. The use of a 70-degree rigid sphere cone forebody aeroshell, a supersonic disk-gap-band parachute deployed within a particular range of Mach number and dynamic pressure, and even the particular thermal protection system material, are all based on 50-year-old developments. Recent missions to Mars have pushed the bounds of those systems such that enabling larger payloads to the surface now requires new technology developments. In the case of human scale missions, requiring landed payloads of 20 to 40 mt, or even human precursors, with landed usable payloads of 5 to 10 mt, a shift in the entire entry architecture paradigm is needed. NASA’s internal Human Architecture Team (HAT) is conducting ongoing assessments of the approaches and technologies that may allow humans to someday explore the surface of the Red Planet. This team includes experts in propulsion, power, flight mechanics, structures, surface operations, habitat design, systems engineering, and numerous other disciplines. The team’s charter is to determine feasible architectures (from Earth launch to the Mars surface, and return) for sending humans to Mars, which will in turn define the requirements for technology development in the next two decades. The work presented herein was performed within the Mars sub-team of the multi-Center HAT, in 2011 and early 2012. II. BACKGROUND Methods for landing humans on Mars have been studied for decades. At first, the concepts required farfetched systems that defied the laws of physics. Fortunately, most studies over the past 20-30 years have the advantage of improved knowledge in some aspect of the problem, such as the environments, the way humans live in space, or the performance of interplanetary flight systems. Meanwhile, technology improvements and applying new capabilities to the problem can reveal novel solutions. The existence of system models, in some cases validated by ground or flight tests, enables technology impacts to be assessed in the context of the overall mission. Recent studies