Stationkeeping in the Space Shuttle middeck, preliminary design for the dice bus module

grantor: University of TorontoThe Space Shuttle middeck is an unlikely place to find a free-floating satellite. That, however, is just what DICE proposes to be: an untethered free-flyer under astronaut supervision. In support of the DICE project, this thesis examines the disturbance forces to which that free-flyer would fall prey, proposes a design for an actuation system which would counter those disturbances, and simulates the control of this actuation system. From a survey of middeck disturbance forces, five significant ones are examined: middeck air circulation, solar radiation pressure, atmospheric drag, gravity gradient torque, and orbital offset between Shuttle Orbiter and DICE mass centers. A simulation of these forces is created in XMath. Middeck air circulation proves to be the greatest disturbance, exerting forces up to 10$\sp{-3}$ N and torques up to 10$\sp{-4}$ Nm. In reply to these disturbances, an actuation system is proposed. It re-circulates middeck cabin air through the DICE bus and ejects it through 3 nozzle clusters in order to produce a net thrust. The airflow created by such an actuation system is characterised, while mock-up conditions, thruster location, and valve position are varied. The force output of one nozzle on the mock-up most faithful to current design is measured to be 10$\sp{-2}$ N.M.A.Sc