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Fig. 1. Reachable regions from Sun-EMB LI and L2 points and potential targets Presented at 69" International Astronautical Congress (IAC), Bremen, Germany, 1-5 October 2018 Copyright 2018 by P. Machuca, J.P. Sanchez, J.J. Masdemont, and G. Gomez. Table 2. AV and TOF requirements for reachable asteroids (CR3BP, impulsive maneuvers)

Figure 1 Reachable regions from Sun-EMB LI and L2 points and potential targets Presented at 69" International Astronautical Congress (IAC), Bremen, Germany, 1-5 October 2018 Copyright 2018 by P. Machuca, J.P. Sanchez, J.J. Masdemont, and G. Gomez. Table 2. AV and TOF requirements for reachable asteroids (CR3BP, impulsive maneuvers)

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which can be used to estimate the initial AV (direction and magnitude) required to achieve a desired final condition. If the required AV, however, exceeds the available AV for a maneuver (provided by the genetic algorithm), the STM can also be used to estimate only the direction of the required AV. For such purpose, the initial velocity can be expressed (see Eq. (10)) in terms of its norm, |(t))|, and two angles representing its direction, for instance, € and @ (elevation with respect to the Sun- EMB plane, and in-plane azimuth):
which can be used to estimate the initial AV (direction and magnitude) required to achieve a desired final condition. If the required AV, however, exceeds the available AV for a maneuver (provided by the genetic algorithm), the STM can also be used to estimate only the direction of the required AV. For such purpose, the initial velocity can be expressed (see Eq. (10)) in terms of its norm, |(t))|, and two angles representing its direction, for instance, € and @ (elevation with respect to the Sun- EMB plane, and in-plane azimuth):
Finally, the highest-fidelity quasi-impulsive model considered in this work uses the second intermediate model as a reference, and now maneuvers are modeled as 20-min continuous and constant thrust arcs of at most 5 mN in magnitude, exerted in a fixed direction in the CR3BP synodic reference frame. Each thrust arc is initiated at the time of the 1.5-m/s maneuvers in the first intermediate model, and a continuous thrust force is then exerted over the span of 20 minutes. The constant direction and magnitude of each thrust arc are also determined through an STM differential corrector, but the equations of motion are modified to include the effect of the thrust. The EoM describing the dynamics of spacecraft during a thrusting arc are summarized in Eq. (13):
Finally, the highest-fidelity quasi-impulsive model considered in this work uses the second intermediate model as a reference, and now maneuvers are modeled as 20-min continuous and constant thrust arcs of at most 5 mN in magnitude, exerted in a fixed direction in the CR3BP synodic reference frame. Each thrust arc is initiated at the time of the 1.5-m/s maneuvers in the first intermediate model, and a continuous thrust force is then exerted over the span of 20 minutes. The constant direction and magnitude of each thrust arc are also determined through an STM differential corrector, but the equations of motion are modified to include the effect of the thrust. The EoM describing the dynamics of spacecraft during a thrusting arc are summarized in Eq. (13):
Table 1. On-board component performance
Table 1. On-board component performance
Fig. 4. 2016 CZ31 encounter trajectory in CR3BP and ephemeris models (impulsive maneuvers) Fig. 3. AV and TOF requirements for asteroid 2016 CZ31 from L1 (ephemeris, impulsive maneuvers)
Fig. 4. 2016 CZ31 encounter trajectory in CR3BP and ephemeris models (impulsive maneuvers) Fig. 3. AV and TOF requirements for asteroid 2016 CZ31 from L1 (ephemeris, impulsive maneuvers)
Fig. 5. AV and TOF requirements for asteroid 2016 CZ31 from L1 (CR3BP, high-fidelity thruster model)
Fig. 5. AV and TOF requirements for asteroid 2016 CZ31 from L1 (CR3BP, high-fidelity thruster model)
As an example of how the direct optimization solver refines the initial guess, Fig. 7 illustrates the history of the thrust magnitude (in the initial guess and in the optimal solution) associated to the left-most departure point in Fig. 6:
As an example of how the direct optimization solver refines the initial guess, Fig. 7 illustrates the history of the thrust magnitude (in the initial guess and in the optimal solution) associated to the left-most departure point in Fig. 6:
Table 3. Best-case error ellipses for asteroids flown by autonomously (CR3BP, impulsive maneuvers)
Table 3. Best-case error ellipses for asteroids flown by autonomously (CR3BP, impulsive maneuvers)
Related topics:
Aerospace EngineeringGeologyNear Earth AsteroidsAutonomous navigation
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