ESA Document - Emits - ESA

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Operational Requirements
It shall be possible to command the TV in an automatic way
TV shall be controllable from Earth
TV shall be controllable by the crew
Crew shall be able to override the automatic control
EVA operations shall be kept to a minimum during transfer and orbiting around Mars phases
Capability of inspecting the the external and internal parts of the vehicle shall be provided
TV shall provide means for corrective and preventive maintenance
Crew time dedicated to maintenance shall be minimised
On-board training capabilities shall be provided
Assembly in orbit
Assembly in orbit shall be as automated as possible
0.00
Assembly shall be performed in LEO
Capability for verification on orbit shall be provided
* all connections shall be verified
* all functions shall be verified
Replace/Repair capability of system modules shall be provided during the assembly phase to ensure full functionality and
redundancy prior to committing to departure
400.00 km
Assembly phase shall kept as short as possible
Planetary Protection Requirements
For the forward contamination:
1.) The probability of an impact on Mars by any part of the launch vehicle (also launch from LEO in that case) shall not
exceed 1E-4
2.) If the Mars orbiting spacecraft does not meet the Viking pre-sterilization bioburden levels the probability of an impact
on Mars shall not exceed 1E-2 for the first 20 years of the mission, and shall not eceed 5E-2 for the time between 20 and 50
For backward contamination:
1.) All sample material returned from Mars shall be contained, and containment shall be verified before entering the Earth-
Moon system
2.) It shall be possible to isolate the surface crew from the rest of the crew on the habitation module for a TBD period of time
after returning from the surface of Mars.
3.) Contamination of the THM shall be avoided during all mission phases (in that respect, docking the ascent vehicle and
transfer of crew and material from there to the habitation module is critical)
Interface requirements
2.00 2.00 Year
Interfaces between assembly elements shall be kept to a minimum to simplify the assembly
THM shall be as independent as possible from the Propulsion Transfer Stages
THM shall provide interfaces with the ERC, allowing the crew to pass from THM to ERC and back
THM shall provide interfaces with the MEV, allowing the crew to pass from THM to MEV and back
THM shall provide interface with the Propulsion Transfer Stages to transmit the loads and commands
THM shall act as data relay between the MEV and Earth
THM shall provide housekeeping functions to the rest of the mission elements (ERC, MEV) when they are in stand by
Interfaces shall be standarised
Propulsion
All propulsion stages shall be designed to provided the required trajectory changes at each mission phase
Staging shall be considered within each main propulsive manoeuvre (TMI, MOI, TEI)
Cryogenic stages shall be considered for TMI
Table 3-1: Transfer Vehicle high level requirements
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 127 of 422
After the realisation of the study, it was discovered that some of these requirements cannot be
fulfilled with the proposed design. For example:
• Mission success requirement cannot be evaluated at this stage
• Assembly in orbit cannot be performed in less than 2 years even in the most optimistic
scenario
• Lifetime of the different modules will have to be set after the assembly in-orbit sequence
is defined
• Abort is not possible during all the mission phases
3.1.2 System design drivers
The THM main design drivers are:
• The habitability requirements, which determine the size of the vehicle. A minimum of 25
m 3 has to be provided for each astronaut. It leads to a total pressurised volume of 450 m 3
• It is the main payload for the propulsion module, so its mass has to be as low as possible
• High level of closure of the life support system to reduce the total mass
• Launcher constraints in terms of dimensions