SolSTUS: Solar Source Thermal Upper Stage

During the past academic year the members of Utah State University's Space Systems Design class have worked on the design of SolSTUS (Solar Source Thermal Upper Stage), a solar propulsion system that could be carried into low earth orbit by small launch vehicles and still carry useful payloads into higher energy orbits or interplanetary missions. To demonstrate the capabilities of the SolSTUS the class worked to meet the requirements of a specific design reference mission. The reference mission was a lunar mapping and science mission launched from a Taurus launch vehicle. Several aspects of the solar thermal propulsion concept were quite challenging. The major driving requirement in the design of this system was the volume of available launch vehicle shrouds. Because of the low density of the hydrogen used as propellant, we could not fit within a standard Taurus shroud [1]. Other challenging areas of the design were the storage of propellants at cryogenic temperatures, concentrating the solar radiation to heat the propellant, low values of thrust, long time periods required to complete the orbit transfer, and the deployment of solar collectors. This design is a system design and did not deal with the detailed development of individual components needed for use on a solar thermal rocket.