| Summary: | The research is concerned with investigating the storage and usage of liquid
Hydrogen and Oxygen over a long duration. For this purpose a mission was defined where
these two
propellants are used to transport a six man crew to Mars and back.
The mission duration is a total of 972 days in length with a stopover time at Mars
of 454
days. A baseline spacecraft is designed. The two driving philosophies behind the
design are reliability and reusability. This baseline spacecraft design was used a a basis
for
analysing the extreme thermal environment and its impact on the propellant storage
temperatures. Also it allowed the calculation of mass and propellant budgets.
It was found that the
Hydrogen fuel undergoes a change of phase when the vehicle
is
orbiting Mars. Hence a escape manoeuvre trajectory simulation was performed which
analysed the escape trajectory, acceleration and duration, and assessed the impact on the
initial Earth launch
propellant budget.
I addition, a number of trade-offs were performed in order to increase the
efficiency of the propulsion system from its nominal design in which the Hydrogen gas is
allowed to
expand directly from the storage tanks through the engine. The optimum
arrangement that was found was to bleed the gas into a small high pressure tank and allow
the fuel to be heated
by waste heat from the onboard nuclear reactor.
The results indicated that not
only does this provide a performance increase over
the nominal
system but also the amount of propellant required for this bum is smaller than
the storable
options considered in the literature.
Hence this
analysis demonstrates that Hydrogen and Oxygen can be stored and
used over
long periods, and that they can still provide a better propellant performance than
storable
options, even with the increased mass penalty associated with using them on a
mission such a this one.
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