EARTH TO MARS ABORT ANALYSIS FOR HUMAN MARS MISSIONS

Future human exploration missions to Mars are being studied by NASA and industry. Several approaches to the Mars mission are being examined that use various types of propulsion for the different phases of the mission. The choice and implementation of certain propulsion systems can significantly impact mission performance in terms of trip time, spacecraft mass, and especially mission abort capability. Understanding the trajectory requirements relative to the round-trip Earth to Mars mission opportunities in the 2030's and beyond is important in order to determine the impact of trajectory abort capability. Additionally, some propulsion choices for the crew vehicle can enable mission abort trajectories while others will most likely provide less flexibility and increase mission risk. This paper focuses on recent modeling of Earth to Mars abort scenarios for human missions to determine the capability to provide fast returns to Earth. The modeling assumed that the abort would occur after the Mars crew vehicle has been injected along the path to Mars (i.e., after the Trans Mars Injection (TMI) burn). These aborts have been defined as well as the timing of fly-by aborts to quickly return crew to Earth. These abort trajectory studies are based on missions NASA defined during the Evolvable Mars Campaign (EMC) with crew going to Mars in 2033, 2039, 2043 and 2048. Detailed trajectory analysis was performed with the NASA Copernicus program for the several crew missions that were in the EMC as well as other new missions being considered using finite-burn low thrust electric propulsion. The goal was to determine how the heliocentric trajectory elements change and the "abort trajectory" impulse requirements. Abort scenarios that were studied included fast returns N-days after TMI as well as fly-by aborts and multiple revolution cases, using all available propellants (e.g., main propulsion system and reaction control system (RCS)) to provide the required abort velocity change. Trajectories were investigated for impulsive maneuvers and for finite burn cases and the abort timelines for each are examined and compared. This paper and presentation will focus on the Copernicus trajectory analysis results that were performed to determine the abort trajectories that altered the primary mission to return to Earth as soon as possible.