ESA Document - Emits - ESA

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5 OVERALL CONCLUSIONS
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 401 of 422
A design case for a Human Mission to Mars has been analysed. Although this does not represent
a “ reference” ESA mission, it contains several design elements of general applicability.
The understanding of the main technical issues and the relevant design elements will allow
future definition of a reference mission and a more comprehensive exploration plan.
In particular, the issues of life support, radiation, long permanence in space, internal habitats and
overall vehicle configurations, entry descent and landing, Martian surface operations, assembly
in Earth orbit, etc., as far as the selected design case is concerned, have been tackled in this study
and design solutions proposed.
Several simplified models have been created to deal with the issues and allow sensitivity analysis
of the main mission parameters.
Whenever possible, preference in the design has been given to existing technologies or those
considered within reach in relatively short time. This is to achieve results that can be trusted in
this phase and to not rely on speculations on performance.
A few general conclusions can be drawn from the exercise:
• Even the simplest mission based on very limited functions and capability leads to
extremely large and massive vehicles and requires assembly in Earth orbit before
departure.
• The most critical technical showstopper for such a mission is the overall vehicle
assembly time in LEO that could result in unacceptable phasing of subsequent
missions and lead to unacceptable ageing before departure.
• A design point exists for an entirely “ chemical” mission (e.g. all based on chemical
propulsion). However, this gives a rather high mass in LEO (above 1000 tonnes)
and as a consequence, high time of assembly in LEO.
• Launcher availability is critical. The study assumed that a launcher with the
performance of Energia would be available for most of the launches. If this
assumption is wrong, a very high penalty on the mission is expected.
• High closure of the life support system (e.g. recycling) is a must. The penalty
associated with an open system would be too big for such a mission.
• The reason for the high overall mass of the mission stems from the very large dry
mass of the Transfer Habitation Module and the relative inefficiency of the chemical
propulsion.
• Among the possible alternatives not requiring technology leaps, aerobraking and
aerocapture have been briefly investigated. It has been discovered that the
implementation of these techniques will require large changes in the vehicle designs
as compared to the chemical case. The detailed analysis of these options was
considered outside the of this first study and will be performed in later phases.
• The verification of safety requirements has proven impossible without an overall risk
model. However, mission abort cases have been investigated and the design has
taken into account failure cases to a certain extent. Failures in the propulsion system
cannot be recovered without unacceptable penalty on the mission; therefore systems
with very high reliability need to be implemented.
As already mentioned, the design case analysed represents an oversimplified mission. Among
the limitations of this approach, the following should be emphasised: