Aerobraking Cost/Risk Decisions

Three missions have successfully used aerobraking to reduce the spacecraft orbit period and achieve the desired orbit geometry. A fourth, Mars Reconnaissance Orbiter, will employ aerobraking following its orbit insertion in March, 2006. The propellant mass reductions enabled by the aerobraking technique allow the use of smaller launch systems, which translate to significant savings in launch costs for flight projects. However, there is a significant increase in mission risk associated with the use of aerobraking. Flying a spacecraft through a planetary atmosphere hundreds of times during months of aroundthe-clock operations places the spacecraft in harm’s way, and is extraordinarily demanding on the flight team. There is a cost/risk trade that must be evaluated when a project is choosing between a mission baseline that includes aerobraking, or selecting a larger launch vehicle to enable purely propulsive orbit insertion. This paper provides a brief history of past and future aerobraking missions, describes the aerobraking technique, summarizes the costs associated with aerobraking, and concludes with a suggested methodology for evaluating the cost/risk trade when selecting the aerobraking approach. * Deputy Manager, Phoenix Project, Jet Propulsion Laboratory, California Institute of Technology # Langley Professor, Planetary Atmospheric and Entry Sciences, National Institute of Aerospace