Post-MECO Propulsion System Requirements for Placement of an STS External Tank in Low Earth Orbit

This paper discusses the findings of a series of computer simulations carried out at the National Institute of Standards and Technology to investigate the requirements for powered flight of the external tank following separation from the Shuttle orbiter at main engine cutoff (MECO). The object of the investigation was to determine the minimum thrust and fuel requirements for an autonomous exterior propulsion package attached to the external tank to avoid reentry on the critical first orbit, and to place the tank in a short term stable orbit from which customary orbit maintenance procedures may be carried out. It is shown that a 1000 lbf (4450 N) hydrogen/oxygen thruster is capable of boosting the tank to a transfer orbit with an apogee of 206 km and a perigee of 159 km by means of expending a 1100 lbm (500 kg) propellant at the initial orbit apogee following MECO. The subsequent orbit will have a decay time of 46 hours (32 orbits) to reentry under solar maximum conditions. Estimates for propellant mass required for subsequent boost to a 500 km altitude storage orbit are presented.