Mission Plan The vehicle is assumed to begin from LEO. Assembled there from parts placed in orbit by commercial ELVs (Expendable Launch Vehicles), the vehicle will have two stages, a storage/power module and a crew module sized for a crew of 6 (3 couples). The first stage propellant tanks provide the delta-v to go from LEO to HEEO (High Elliptical Earth Orbit). A typical HEEO might have its perigee in LEO, and its apogee near the Moon's orbit. The orbital period would be some harmonic of the Moon's period, so as to minimize lunar perturbations. The second stage separates and does a burn at perigee, placing the vehicle in MTO (Mars Transfer Orbit). The reason for leaving the first stage in HEEO will be explained later. (Note: The total launches required could be substantially reduced if a low-thrust, high Isp OTV was available to take the big aerobrake to HEEO. However, it was decided that in this paper, we would only consider things that are or are likely to be commercially available.) At this point, a decision must be made as to the trip time. Starting from a HEEO with a period of half the lunar period (first stage delta-v = 3125 m/s), the minimum delta-v (Hohmann transfer) required for a generic mission is 470 m/s. However, as can be seen from Fig. 2, it is possible to shave quite a bit off the trip time for just a little extra delta-v. A balance must be struck between the desire for a short trip time, and the cost of placing the extra fuel in LEO (see Fig. 3). Also, increasing the departure delta-v increases the arrival delta-v at LMO (Low Mars Orbit) as seen in Fig. 4. This increases both the heat load on, and the size of, the aerobrake, and the g- load that the crew must endure during aerobraking.
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