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

3 TALARIS CGSE Design Framework
After the major architecture decisions had been made for the TALARIS spacecraft emulator propulsion
system, the next step was detailed design. The goal of this development process was not to develop a
radically new propulsion system, which would have been extremely difficult given the limited budget
and relatively short deadlines of the TALARIS project; cold gas propulsion technology is mature enough
that there is little room for drastic improvement. Rather, the aim of the process described in this thesis
was to make specific choices that most effectively satisfied the particular needs of the TALARIS project
while working within the generally well-established framework of cold gas propulsion system design.
3.1 CGSE Requirements Definition
The architecture definition process had placed some constraints on the design problem, such as the
decision that the spacecraft emulator propulsion system would be a cold gas propulsion system, as well
as a set of functional requirements. But in order to have definite targets to which to design the TALARIS
CGSE, the process of requirements definition had to be carried further forward. The requirements
already determined were used to derive quantifiable performance requirements.
3.1.1 Functional Requirements
The decisions to (1) divide the TALARIS propulsion tasks into weight relief and spacecraft emulation,
each performed by a separate system, and (2) design for the performance of a hover hop led to three
main functional requirements for the TALARIS spacecraft emulator propulsion system. They were:
(1) The CGSE shall lift the TALARIS hopper’s lunar weight, defined as 1/6 of its Earth weight.
Though the long-term goals for the TALARIS project include simulation of operations on a range of target
bodies, the short deadlines for the GLXP made simulation of lunar operations the top priority.
Furthermore, a CGSE capable of lifting the TALARIS hopper under lunar gravity could also function for
many other targets with even lower gravities, including Saturn’s moon Titan 2
or a variety of asteroids, if
EDF output could be increased to provide a higher fraction of weight relief. If later operations on a body
with higher gravity than the Moon, such as Mars, were desired, upgrades would be necessary unless the
CGSE far exceeded its design goals. However, it was essential to set initial numerical design targets for
the CGSE, and designing for lunar gravity was selected for the requirement.
2
Titan has a surface gravity of 0.138