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ESA Document - Emits - ESA

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s<br />

• DCS treatment chamber<br />

• Safe area in case of contingency<br />

• Additional level of containment<br />

4.3.3.8.4 Investigation of alternative inert gases<br />

HMM<br />

Assessment Study<br />

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

February 2004<br />

page 276 of 422<br />

In the course of this study, alternative inert gases were investigated with the objective of<br />

minimising DCS risk and prebreathing time without compromising safety. Previous studies with<br />

rats demonstrated that the use of a mix of inert gases (nitrogen/argon, argon/helium,<br />

nitrogen/helium) does not represent any advantage over the use of one of the most advantageous<br />

inert gases such as helium. It was shown that the total pressure of gases except oxygen in the<br />

tissue is important and not the partial pressure of the individual gases except oxygen that are<br />

dissolved in the tissue. Neon has been suggested as the most advantageous inert gas for space<br />

flight applications; however, there have not been any reports of tests with neon as inert gas. Most<br />

likely reason for the absence of such data is the price of neon.<br />

4.3.3.8.5 Contingency supply<br />

The use of an open-loop system reduces the need for an emergency supply. However, seven days<br />

have been taken in this study as the timeframe expected to prepare for ascent from the Martian<br />

surface and journey to the THM.<br />

Currently, the assumption is that the supply would be sufficient until the crew has been able to<br />

overcome the contingency situation or to return to the THM using MAV resources.<br />

4.3.3.8.6 In-situ resource utilization (ISRU)<br />

ISRU has not been considered during this phase of the study.<br />

4.3.3.9 Waste management strategy<br />

Waste has to be stabilized and stored on the surface. No recycling or return of the waste is<br />

envisaged to minimise down and up mass for the life support.<br />

Currently, the strategy is not compliant with the Planetary Protection rules and it is necessary to<br />

further study the waste handling strategy on the Martian surface. The only measure taken into<br />

account is to seal the SHM prior to the departure.<br />

4.3.3.10 Baseline design<br />

The life support system is an open-loop life support system with limited regeneration. Water is<br />

provided by the fuel cells. Oxygen is stored with the oxygen needed for power generation in the<br />

fuel cells. All subsystems of the life support system are designed as open loop with replaceable<br />

consumables. The actual technical design of the subsystems has not been yet and needs further<br />

investigation.

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