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

this would be achieved with the regulator set at its maximum outlet pressure of 614.7 psia, and if this
maximum thrust level was higher than desired, the optimum pressure level at which to set the regulator
output would be determined.
A second characteristic to be measured in the single-stream tests was response time. As mentioned in
section 4.2.1, the SV128’s rating of 30 to 60 ms was on the borderline of acceptability for the CGSE. It
was important to know where in that range the valve actually performed. Thus, measuring the time
between the actuation signal and the point in time at which the thrust had reached its target level – full
thrust for opening, or zero thrust for closing – was necessary.
The thrust and timing measurements were to be combined to determine impulse characteristics of the
thruster, as shown in Figure 5-1 below.
Figure 5-1. Measurements made in single-stream thruster characterization tests [38].
In particular, a major goal of the single-stream tests was to determine the minimum pulse width for
which the actual measured impulse equaled the commanded impulse. This minimum pulse width,
combined with the thrust level available at the final chosen chamber pressure setting, would thus
determine the minimum impulse bit of the CGSE.
5.2 Testing Setup and Procedures
5.2.1 Instrumentation
Instrumentation was of paramount concern in the construction of the single-stream test apparatus;
many different sensors were needed to record the data of interest. Pressure was measured immediately
upstream of the solenoid valve as well as immediately downstream, before the gas entered the nozzle.
To take these measurements, four-way cross fittings were attached to both the inlet and the outlet of
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