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

variables (such as number of thrusters firing) were changed. This effect is illustrated in Figure 6-8, for
both a single horizontal thruster and the set of all four vertical thrusters.
Figure 6-8. CGSE thrust decrease with gas usage.
In the tests from which this data was collected, the flight tanks were filled to approximately 4500 psia,
and the thruster(s) were fired for 1 s pulses at 2 s intervals until the pressure across the flight regulator
equalized at the output set pressure of approximately 600 psia. On the y axis, thrust is normalized
against the thrust measured for the first firing in a given test. On the x axis, gas usage is tracked with the
unit of thruster-seconds. One thruster firing for one second consumes one thruster-second of gas, one
thruster firing for two seconds and two thrusters firing for one second both consume two thruster-
seconds of gas, etc. Figure 6-8 shows that there is a general decrease in thrust level as gas is consumed
from the tanks. This decrease appears to be more severe at an earlier stage for the four thrusters firing
together; the single thruster firing alone maintained a higher percentage of its initial thrust for a longer
period, although it did drop off sharply at the end of the test.
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