ESA Document - Emits - ESA
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ESA Document - Emits - ESA

ESA Document - Emits - ESA ESA Document - Emits - ESA

emits.esa.int
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s Trajectory Surface stay duration Propulsion Return approach Trade-offs Options Conjunction Opposition Venus swing-by Low thrust Orbit insertion around Mars Orbit around Mars MEV release Split / All up Microgravity countermeasures Long stay Short stay Chemical Storable Cryogenic NTP SEP NEP THM and ERC inserted around Earth THM discarded, ERC inserted THM discarded, ERC direct entry Propulsive Aerocapture Aerobraking Circular High elliptical orbit From circular orbit From high elliptical orbit Split scenario All up scenario Spinning spacecraft Centrifuge Crew number 3 to 6 2.7.5 Basic assumptions for trade-offs Table 2-6: Trade-offs and options for the study case HMM Assessment Study Report: CDF-20(A) February 2004 page 46 of 422 The architecture trade-offs were performed along the study in parallel to the evolution of the design. However, an initial screening of the options was done to reduce the options. For this activity, a starting vehicle design point was required. The numbers used at the beginning for this purpose are the following:

s 2.7.5.1 Mission elements dry masses Mission Element Mass (tonnes) THM 55.4 (dry) MEV 29 (wet) ERC 10.2 (wet) HMM Assessment Study Report: CDF-20(A) February 2004 page 47 of 422 Table 2-7: Mission Elements masses These figures are derived mainly from literature or from preliminary simplified computations, and just represent a starting point. 2.7.5.2 Life support system for the THM The levels of closure assumed for the life support system are the following: Element Level of closure (%) Oxygen 95 Potable water 95 Grey water (condensate, used hygiene water) 95 Yellow water (water in contact with urine) 95 Black water (water in contact with faeces) 20 Solid organic waste to food 20 Solid inorganic waste 0 Packaging reuse 0 Table 2-8: Life support system level of closure Taking these levels of closure into account and typical mission duration of 950 days, the consumables required for a crew of six for the whole mission are 10.2 tonnes. 2.7.5.3 Propulsion system A modular design for the propulsion module has been assumed, that is, separate propulsion systems are used for each main propulsive manoeuvre. This approach allows the jettisoning of each propulsion module after its usage. Within each main propulsive manoeuvre, a staging approach is also followed, so that the manoeuvre is split into several stages to increase the efficiency of the system. This approach allows you to get rid of the stages once they have been used and also reduces the gravity losses as the time required for each burn is lower. Therefore, the system is assumed to be as follows: • TMI module (3 stages) • MOI module (2 stages) • TEI module (1 stage) In general, each propulsion stage will be bigger than the launcher capabilities in terms of mass, so, each stage will have to be split into submodules, called stacks. With this approach it is expected to reduce the cost of the system, as the same design will be used for all the stacks. Regarding the propulsion technologies used, the values assumed are as shown in Table 2-9:

s<br />

Trajectory<br />

Surface stay duration<br />

Propulsion<br />

Return approach<br />

Trade-offs Options<br />

Conjunction<br />

Opposition<br />

Venus swing-by<br />

Low thrust<br />

Orbit insertion around Mars<br />

Orbit around Mars<br />

MEV release<br />

Split / All up<br />

Microgravity countermeasures<br />

Long stay<br />

Short stay<br />

Chemical<br />

Storable<br />

Cryogenic<br />

NTP<br />

SEP<br />

NEP<br />

THM and ERC inserted around<br />

Earth<br />

THM discarded, ERC inserted<br />

THM discarded, ERC direct entry<br />

Propulsive<br />

Aerocapture<br />

Aerobraking<br />

Circular<br />

High elliptical orbit<br />

From circular orbit<br />

From high elliptical orbit<br />

Split scenario<br />

All up scenario<br />

Spinning spacecraft<br />

Centrifuge<br />

Crew number 3 to 6<br />

2.7.5 Basic assumptions for trade-offs<br />

Table 2-6: Trade-offs and options for the study case<br />

HMM<br />

Assessment Study<br />

Report: CDF-20(A)<br />

February 2004<br />

page 46 of 422<br />

The architecture trade-offs were performed along the study in parallel to the evolution of the<br />

design. However, an initial screening of the options was done to reduce the options. For this<br />

activity, a starting vehicle design point was required. The numbers used at the beginning for this<br />

purpose are the following:

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