For spacecraft departing the Earth - Moon system, lunar flybys can significantly increase the hyperbolic escape energy (C3, in km (exp 2) /sec (exp 2) ) for a modest increase in flight time. Within approx 2 months, lunar flybys can produce a C3 of approx 2. Over 4 - 6 months, lunar flybys alone can increase the C3 to approx 4.5, or they can provide for additional periapsis burns to increase the C3 from approx 2 -3 to 10 or more, suitable for planetary missions. A lunar flyby departure can be followed by additional delta -V (such as that efficiently provided by a low thrust system, eg. Solar Electric Propulsion (SEP)) to raise the Earth - relative velocity (at a ratio of more than 2:1) before a subsequent Earth flyby, which redirects that velocity to a more distant target, all within not more than a year. This paper describes the applicability of lunar flybys for different flight times and propulsion systems, and illustrates this with instances of past usage and future possibilities. Examples discussed include ISEE-3, Nozomi, STEREO, 2018 Mars studies (which showed an 8% payload increase), and missions to Near Earth Objects (NEOs). In addition, the options for the achieving the initial lunar flyby are systematically discussed, with a view towards their practical use within a compact launch period. In particular, we show that launches to geosynchronous transfer orbit (GTO) as a secondary payload provide a feasible means of obtaining a lunar flyby for an acceptable cost, even for SEP systems that cannot easily deliver large delta-Vs at periapsis. Taken together, these results comprise a myriad of options for increasing the mission performance, by the efficient use of lunar flybys within an acceptable extension of the flight time.


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    Titel :

    Using Gravity Assists in the Earth-moon System as a Gateway to the Solar System


    Beteiligte:
    McElrath, Timothy P. (Autor:in) / Lantoine, Gregory (Autor:in) / Landau, Damon (Autor:in) / Grebow, Dan (Autor:in) / Strange, Nathan (Autor:in) / Wilson, Roby (Autor:in) / Sims, Jon (Autor:in)

    Kongress:

    Global Space Exploration Conference ; 2012 ; Washington, DC, United States


    Erscheinungsdatum :

    2012-05-22


    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Keine Angabe


    Sprache :

    Englisch




    Using Gravity Assists in the Earth-moon System as a Gateway to the Solar System

    McElrath, Tim / Lantoine, Gregory / Landau, Damon et al. | NTRS | 2012





    Trajectory Design in the Sun-Earth-Moon System Using Multiple Lunar Gravity Assists

    Wilson, R. / Howell, K. / American Institute of Aeronautics and Astronautics et al. | British Library Conference Proceedings | 1996