ESA Document - Emits - ESA

s
Total Mass to LEO (Ton)
1240
1235
1230
1225
1220
1215
1210
1205
1200
0 2000 4000 6000 8000 10000 12000 14000 16000
Altitude (km)
Radiation increment %
25
20
15
10
5
0
0 2000 4000 6000 8000 10000 12000 14000 16000
Altitude (km)
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 60 of 422
Figure 2-27: Orbit around Mars
Figure 3-32 shows on the left that the variation in the total mass to LEO versus altitude is
negligible. The dose received by the astronauts above the low Mars orbit, as the effectiveness of
the planet shielding is reduced. Orbit decay is not a problem above 500 km.
The baseline of 500 km circular has therefore been chosen and the inclination of the final orbit
has been taken as the optimal one for departure.
2.7.6.7 MEV release
There are two possibilities for releasing of the MEV: while still in high elliptical orbit before the
final orbit acquisition, or once the orbit has been circularized. In principle, the first option and
reduce mass, as the mass to be put into the circular orbit is lower.
MEV released from HEO MEV released from LMO
Mass to LEO (tonne) 1312 1336
Table 2-17: Mass to LEO as function of the MEV release strategy
Release from high elliptical orbit provides very little mass advantage, which is not compensated
by the increment in complexity. Furthermore, the TV would have little time (the surface stay
time) to reach the final rendezvous orbit with the MAV from release, which significantly raises
the risk of the mission. Finally, release may not be possible at arrival because of dust storms, so
the TV would have to wait in HEO until the landing is feasible.
A MEV release from the final circular orbit has been therefore selected.
2.7.6.8 All-up / Split scenarios
An all-up scenario is defined as one in which the mission composite is sent to Mars in one
vehicle, with all the required vehicles and infrastructures in one go. The split scenario is the one
in which some of the infrastructures and/or vehicles are sent in a different composite vehicle.
Two possible split scenarios have been considered:
1. Two identical vehicles with three crew members each, one carrying a MEV and both
carrying an ERC.
2. One vehicle including THM+ERC and one only the MEV, which will have to
rendezvous with the THM+ERC in Mars orbit before descent.
The means to come back and consumables have to be included in every crewed vehicle. In this
way the crew can survive if any of the rendezvous manoeuvres fails.