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

Figure 5-7 illustrates several aspects of the pressure-thrust relationship that were revealed through
single-stream testing. First, there was an approximately linear relationship between thruster output and
chamber pressure, as shown in Figure 5-7(b). The maximum thrust attained by the CGSE thruster in the
single-stream tests was 40 N, produced with a chamber pressure of 392 psia, and obtained using the
flight regulator and flight tanks as shown in the Figure 5-6 configuration. However, comparison between
Figure 5-7(a) and Figure 5-7(b) shows that chamber pressure was not the same as the regulator output
set pressure, as had been assumed in the MATLAB model. Rather, there were often significant pressure
losses incurred, and these losses were strongly affected by feed line geometry. For instance, the choked
flow that occurred in the first testing setup (illustrated in Figure 5-3) is clearly visible in Figure 5-7(a),
where the Lab Cylinder (Long Line) points level off at approximately 12 N thrust for all regulator output
set pressures above 400 psia. This did not occur for either of the other testing configurations. However,
the flight tanks and regulator clearly had less pressure loss than the laboratory cylinder and regulator,
since the flight setup was able to produce higher levels of thrust at the same regulator output set
pressures as the laboratory cylinder setup, even without the long choked feed line. As mentioned
before, it was believed that this was due to the low