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

from the higher specific impulse when total impulse requirements are low. Figure 2-7 illustrates this
relationship between system mass and total impulse.
Figure 2-7. Weight/mass of propulsion systems vs. total impulse delivered [24].
The relationship illustrated in Figure 2-7 is reinforced by consideration of the lander testbeds discussed
in section 2.1. The large vehicles that competed in the Northrop Grumman Lunar Lander Challenge used
bipropellant propulsion because those systems can deliver the large amount of impulse needed with the
lowest mass possible. By contrast, the smaller vehicles like the ACAT lander and the NASA test vehicles
used monopropellant and cold gas propulsion, since those systems have better performance in the
lighter weight range.
The design of the GLXP hopper, including size and impulse requirements, has not yet been finalized,
although monopropellant hydrazine has been suggested for its propulsion system [17]. But all three
types of propulsion systems under consideration behave similarly – they all control thrust by varying
propellant flow, and all can be designed to have a pulsed operation mode for attitude control – so the
TALARIS hopper should be able to provide an accurate simulation of the GLXP hopper regardless of the
particular rocket propulsion system chosen for each vehicle.
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