ESA Document - Emits - ESA

s
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 103 of 422
Phases Options
Earth Departure Return to Earth possible
Early Part of Transfer to Mars Quick return to Earth usually possible for about the first
75 days
Later Part of Transfer to Mars Mars swing-by (gravity assist) return to Earth via
opposition-like trajectory
Mars Orbit • Early: Return to Earth opposition-like trajectory
• Later: Wait for normal Earth return opportunity
Mars Descent (not present in the Separate ascent stage and crew module; abort to Mars
present mission, but recommended) orbit
Surface Operations Use Mars ascent stage; if it is inoperable there is no abort
Mars Ascent No practical abort scheme
Trans-Earth Injection No practical abort if main propulsion fails
Transfer to Earth Continue normal return to Earth
2.9.7 Risk acceptability
Table 2-39: Abort possibilities
The purpose of this is to analyse the acceptability of risks and risk reduction options according to
the risk management policy and to determine the appropriate risk reduction strategy.
The results of the preliminary technical risk assessment indicate where the first risk reduction
efforts should be made. Main risk contributors at this stage are shown in Figure 2-58, but the
maximum concern is risks to the crew. Human factors are extremely important for the mission
success. Large uncertainties exist in this context regarding physiology and psychology of the
crew due to the lack of previous experience and information available and the preliminary
definition of the design. This is expected to improve with the availability of more information
and optimisation of the vehicles design, particularly with reference to the failure detection,
warning, caution and recovery systems definition. The public safety of people on Earth is also of
concern.