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Analysing waste gases on a simulated Mars mission

02 December 2014

As part of a project to measure the effects of long-term isolation on astronauts, small groups of individuals have been selected to live in a tiny ‘Habitat’ perched on the upper slope of a volcano in Hawaii to contribute to the understanding of issues that would confront a manned mission to Mars.

As part of the project’s research NASA’s Anne Caraccio studied off-gases from the crew’s trash with a portable Gasmet FTIR gas analyser. She said:  “Waste from the crew’s everyday activities are routinely sorted and stored, but we need to know the composition of the off-gases from these materials for health and safety reasons, and also need to determine whether these gases could be utilised beneficially.” 

The work was undertaken during the second of four HI-SEAS missions which involved living with five other crew members for a period of 120 days in a two-story solar powered dome just 11m in diameter with a small attached workshop. 

The main objective of the second HI-SEAS mission was to evaluate the performance and the social and psychological status of the crew members while living in cramped isolated conditions in a lava rock environment that resembled Mars. Crew members were allowed outside of the Habitat, but in order to do so they had to wear simulated spacesuits and undergo a five minute mock compression/decompression. Since the FTIR gas analyser is portable, it was possible to conduct additional monitoring both inside and outside the Habitat in order to compare data with the waste off-gas measurements. “Size, weight and portability are of major importance on a project such as this, but the main advantage of this technology was its ability to measure a large number of compounds simultaneously; I measured 24 VOCs such as acetaldehyde, methane and ethylene, but the instrument also stores spectra for the measurements so it is possible to retrospectively analyse data if it becomes necessary to look for a particular compound at a later stage,” said Caraccio.

The monitoring provided a clear view of the most important gases within the Habitat. For example, stored waste had the highest relative levels of ethanol (due to crew members’ hygiene wipes and cleaning products) and water vapour (due to residual water from food and plant waste). The laboratory where plants were growing had the lowest relative level of methane. The waste bins had higher relative levels of nitrous oxide and pentane, and the bathroom had the highest levels of acetaldehyde.

All the waste produced during the mission was measured, although this was for a shorter period than would be expected of an actual long duration mission.  The Trash-to-Gas reactor processed HI-SEAS waste simulant at the Kennedy Space Center with results demonstrating that a future reactor would be most efficient with specific material processing cycles to maximise the desired output. Automation will also be needed in the future Trash-to-Gas reactor because the current technology would require too much of a crew member’s logistical time. 

The Trash-to-Gas reactor first converts waste into carbon dioxide, which is then mixed with hydrogen in a Sabatier reaction to produce methane and water. The Kennedy Space Center Trash-to-Gas reactor processed three waste types and produced 9% of the power that would have been needed during the HI-SEAS mission. 


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