Development of a Cold Gas Propulsion System for the ... - SSL - MIT

discussed later in section 6.3.4, this turned out to be somewhat inaccurate, and the trajectory of
actual flights were substantially less smooth than those which were modeled.
• Attitude control was not modeled because the magnitude of disturbances for which corrections
would be necessary was not known. Instead, flight profiles were only considered feasible if the
model indicated that there would be additional gas remaining in the tanks after the planned
maneuvers for the hop, leaving some margin for attitude control.
• The regulator was assumed to be able to provide constant pressure to the low side of the CGSE
throughout an entire hop. In fact, pressure regulators are subject to an effect called droop, in
which the actual outlet pressure decreases below the set outlet pressure as the flow rate
through the regulator increases [51]. Droop can vary greatly for different regulator designs, and
it is usually characterized empirically and documented in a regulator’s specification sheet with a
flow curve. Since a specific regulator had not yet been selected, droop could not be accurately
characterized in the MATLAB model. Instead, it was taken into account later in the component
selection process.
• Equation (4-8) for