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

(2) The CGSE shall propel the hopper horizontally.
This is a key difference between TALARIS and the lunar lander testbeds described in section 2.1.
Although several of the lander testbeds were capable of traveling horizontally, it was not their primary
function. By contrast, horizontal transit over a significant distance is the main goal of hopping, so it was
a major design driver for the TALARIS CGSE from the start.
(3) The CGSE shall provide attitude control for the TALARIS hopper.
TALARIS was designed to simulate the functions of a lunar or planetary hopper as completely as
possible. Since an actual hopper operating off the Earth would have only its rocket propulsion system,
this meant that the TALARIS hopper testbed should ideally rely only on the CGSE for attitude control for
maximum similarity, using the EDFs only for passive weight relief. The goal was to design TALARIS such
that under nominal operations, where the EDFs were providing pure vertical weight relief, the CGSE
would be capable of executing all attitude adjustments necessary to simulate a full hop.
These three functional requirements were the starting point for the requirements flowdown process
described in this section.
3.1.2 TALARIS Flight Profile
A more specific definition of the TALARIS flight profile was necessary to proceed with requirements
flowdown. As defined in section 2.3.1, a hover hop has three phases: vertical ascent, horizontal transit,
and vertical descent. But more precise dimensions had to be assigned to each of these phases.
The TALARIS hopper was primarily designed to simulate the GLXP hopper. However, as discussed in
section 2.3.1, it was known that the GLXP hopper would likely have a propulsion system with a higher
total impulse capability than the TALARIS hopper, largely because the GLXP hopper would not have to
adhere to such strict safety restrictions and could thus use energetic rocket propellants. Thus, the
TALARIS hopper was designed to fly a scaled-down version of the planned GLXP hop that still contained
all the accelerations that the GLXP hopper would experience in order to retain dynamic similarity. A
comparison of the TALARIS and GLXP hops is shown in Figure 3-1.
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