ESA Document - Emits - ESA

s
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 39 of 422
walking-traverses as 1-3 km/h, the maximum distance of EVAs from the Mars Excursion
Vehicle (MEV) would be 5 km for rover-assisted EVAs, and 1 km for walking-traverses. These
distances are in agreement with the requirement to be able to walk back to the MEV from any
location during an EVA if the greatest distance from the MEV is reached at the beginning of an
EVA activity.
2.5.2.5 Number of crew-members required for surface exploration
A typical EVA-day leaves no room for any spacecraft operations and preparation for upcoming
EVAs for the crew members that are performing the EVA. With the requirement of a buddysystem
for EVAs this means that EVAs can only be performed every second day. At the same
time, having only two crew-members on the surface is a single point failure for EVAs in case
one of them becomes incapacitated. The Apollo experience has revealed that EVA activities are
by themselves very demanding (with pulse rates of up to 140 per minute), and produced fatigue
and injuries especially to the fingers, which reduced the performance to an extent of not being
able to remove the spacesuit without help. This, and other potential threats to the performance of
astronauts on the surface of Mars, implies that a third crew-member is highly recommended.
Comparing the timeline of a three crew-member team shows that even with this extra member it
will not be possible to have more than one EVA every second day.
2.5.3 Conclusions
The following recommendations have been issued for the design:
1. The nominal duration of each EVA is 6 hours.
2. Upon landing, 1-2 dedicated EVAs are required for securing the landing site.
3. The maximum distance for walking-traverses (if any) from the MEV is 1 km.
4. The maximum distance for rover-assisted traverses from the MEV is 5 km.
5. The minimum number of field exploration EVAs is two (to revisit a site).
6. The minimum number of crew-members for surface operation is three.
7. The total sample mass returned to Earth in the first human mission to Mars shall be up to
100 kg.
8. One dedicated EVA is required to select the samples to be taken back to Earth, perform
the required activities to prepare the samples for the flight back to Earth, and to collect
deployed equipment.
9. The sample return part of the mission is classified as Planetary Protection Category V,
restricted Earth return.
2.6 Radiation environment
Energetic charged particles with energies in the MeV range are encountered throughout the
Earth’s magnetosphere, in interplanetary space and in the magnetospheres of other planets.
While solar proton events can provide very high particle fluxes over a short period of time, the
radiation belts and cosmic ray fluxes provide a more continuous source of radiation. The