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Accessible NEAs

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Assumptions and Caveats for NHATS-Compliant NEAs

  1. The list of potential mission targets should not be interpreted as a complete list of viable NEAs for an actual human exploration mission. As the NEA orbits are updated, the viable mission targets and their mission parameters will change. To select an actual target and mission scenario, additional constraints must be applied including astronaut health and safety considerations, human space flight architecture elements, their performances and readiness, the physical nature of the target NEA, and mission schedule constraints.

  2. The target NEAs in these tables were identified using a Lambert solution technique. Since no mid course maneuvers, gravity assists or continuous thrust options (e.g. solar electric propulsion) were considered, there are certain to be additional mission options that do not appear within this table.

  3. The trajectory filter parameters were purposely chosen to be highly inclusive in order to provide a broad spectrum of mission possibilities. To pass the trajectory filter and be characterized as NHATS-compliant, a NEA must offer at least one round trip trajectory solution that satisfies the following constraints:

    1. Earth departure date between 2020-01-01 and 2045-12-31
    2. Earth departure C3 less than or equal to 60 km2/sec2
    3. Total mission delta-V (dV) less than or equal to 12 km/s. The total delta-V includes the Earth departure maneuver from a 400 km altitude circular parking orbit, the maneuver to match the NEA's velocity at arrival, the maneuver to depart the NEA and, if necessary, a maneuver to control the atmospheric re-entry speed during Earth return.
    4. Total round trip mission duration less than or equal to 450 days
    5. Minimum stay time at the NEA of 8 days
    6. Earth atmospheric entry speed less than or equal to 12 km/s at an altitude of 125 km

  4. Trajectories are computed using the method of embedded trajectory grids. This provides a comprehensive analysis by stepping through, at 8-day intervals, all combinations of departure dates, outbound flight times, stay times, and inbound flight times. The trajectory calculations are performed using patched conics with Lambert solutions for the spacecraft and with full precision ephemerides for the Earth and NEAs obtained from JPL’s Horizons system.