A safe and low cost cryogenic upper stage design for the Space Shuttle

Abstract

Reusable launch vehicles, such as the Space Shuttle, are presently unable to carry high energy upper stages due to inherent issues associated with liquid hydrogen and oxygen propellant management. Consequently, these advanced launch systems are not able to accommodate future large payloads to geo transfer or synchronous orbit, or to support future manned missions to the Moon and Mars. These unresolved issues associated with hydrogen and oxygen arise from the fact that the cryogenic storage tanks, feed systems, and engine are located inside a closed cargo bay compartment. Therefore cryogenic liquid leakage during tank ground fill operations can result in a potential loss of vehicle. Even a small component leakage can represent unacceptable hazardous condition during loading operations or after an abort landing. The and operations impact of a cryogenic LO2/LH2 upper stage for the Space Shuttle was extensively evaluated in the Shuttle/Centaur program. The program was eventually canceled because of major unresolved issues. Boeing has identified an innovative cryogenic upper stage concept which solved the previous safety showstoppers through in-flight fill of the upper stage storage tanks. In this concept the upper stage is filled with LO2 and LH2 from the main propulsion storage tank after the vehicle has reached a safe altitude (> 160,000 ft) where O2/H2 ignition cannot occur due to the space like low pressure environment. The payload capability of the Space Shuttle to geo transfer orbit (GTO) with the Boeing cryogenic upper stage will be dramatically increased from the present ~ 13,000 Ib. to ~ 28,000 Ib. This large increase in STS payload capability will allow flying large DoD payloads in the future or multiple commercial satellites to reduce operations costs. The expected capability of the Shuttle with the cryogenic upper stage will surpass the present operational capability of foreign and US launchers. This paper presents the status of a conceptual design, resolution of previously identified issues, and performance associated with a cryogenic upper stage inside the Space Shuttle Orbiter.