Exploration missions with a solar bimodal system

This paper reports the results of an examination of planetary missions performed using a solar bimodal power and propulsion system. The Air force Phillips Laboratory has initiated an Integrated Solar Upper Stage (ISUS) technology demonstration program intended to mature solar bimodal technology to flight demonstration. The ISUS development program has focused on decreasing the cost of placing military satellites in high Earth orbits. This is accomplished by providing high specific impulse thrust for orbital transfer of spacecraft launched from smaller and less expensive boosters. This paper, however, reviews the applications of the ISUS technology to NASA solar system exploration missions. Mission analysis is presented showing the capability of the ISUS to deliver payloads from LEO to orbit around the Moon, Mars, Jupiter and Saturn. Both direct and gravity assisted trajectories are included as are mission plans including both staged and unstaged strategies for Earth escape. A minimum mass spacecraft system for solar system exploration is presented, and used as a baseline to develop estimates of potential science payload deliverable to each planetary destination of interest as a function of launch booster capability. Booster fairing packaging considerations are examined. Earth escape time using a variety of perigee-kick orbit transfer strategies is also calculated, as is the communication capability of the ISUS as a function of planetary destination. It is shown that the ISUS offers significant potential as a propulsion system supporting interplanetary exploration. In general, it is found that the optimal trajectories for maximum science return require staging the spacecraft off the ISUS shortly before escape from the Earth. Providing other supporting technologies are developed, such a strategy would also allow the ISUS to be returned to LEO for reuse after each mission.