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

In order to increase the amount of deck space available, the base structure of the second-generation
TALARIS hopper (T-2) was constructed from carbon-fiber composite materials. This allowed for a deck
with nearly twice the area at half the mass of the old T-1 structure. To simplify the organization of
components on the structure, it was decided that the majority of the CGSE should be located beneath
the deck. This left the top of the deck clear for the avionics and the electrical power system, including
the large lithium polymer batteries that powered the EDFs, which had to be frequently removed for
recharging. By contrast, it was expected that most of the CGSE components would not need frequent
adjustments, so they could be placed in less-accessible locations.
The CGSE flight configuration was centered around the Tescom flight regulator. Because the regulator
was so large and heavy, it was bolted securely to the underside of the deck near to the geometric center
of the vehicle, in order to make it as easy as possible to balance the regulator with other components to
keep the center of mass near the geometric center. This also made it possible to have feed line tubes of
the same length with bends of the same angle leading to all of the CGSE thrusters, which made thruster
performance more uniform. These feed lines were made from 0.5 in. OD (0.43 in. ID) tubing; because
they were on the low side of the CGSE, they had a much lower required working pressure than the high
side tubing, so it was possible to use aluminum tubing to save mass. Four feed lines were connected to a
branching manifold made from brass three-way tee fittings attached to the regulator outlet; at the end
of each feed line, one final three-way tee was placed to split the flow to one vertical and one horizontal
thruster. These thruster pairs were placed as far apart as possible (approximately ±6.25 in. in the
vehicle’s Y-axis dimension) to allow for a long torque arm while avoiding interactions between EDF and
CGSE exhaust.
The high side of the CGSE was constructed approximately as shown in Figure 5-5, though without the
four-way instrumentation cross. Also, the tanks were brought slightly closer together and moved out of
the plane of the regulator inlet and the main feed line leading up to it. This made the CGSE slightly more
compact so that all components could fit on the new T-2 structure, but it did require that each of the
two stainless steel tubes leading out of the tanks be reshaped with two plane-changing bends rather
than the single in-plane 90° bend shown in Figure 5-5. Finally, the length of the main high side line to the
regulator was adjusted such that with the regulator at its central position, the fill and shutoff valves
were beneath the hopper deck but near the edge. This made them accessible for operations such as
filling the flight tanks.
The flight configuration of the CGSE is shown in Figure 6-2 below.
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