ASHRAE Journal - July 2020 - 15

TECHNICAL FEATURE

removal system. Carbon dioxide produced by astronauts
through breathing can quickly build up in the conﬁned
space inside the spacesuit. An effective carbon dioxide
removal system using lithium hydroxide canisters is
located on the back of the spacesuit, which maintains a
healthy condition for the astronauts.

Prospects and Concluding Remarks
Whether it is a single spacesuit, space capsules, spacecrafts or ISS, environmental control has been and continues to be a critical component of space missions, and
it is becoming more important as the quest for interplanetary manned missions grows. With space travel
and extraterrestrial habitation soon becoming a reality, ASHRAE is in a unique position to provide industry
direction for indoor environmental quality (IEQ) standards for these facilities.
Because decision-making in space and planetary
expeditions is necessary for mission success and crew
survival, especially in emergencies, IEQ becomes a more
important element in optimizing appropriate environmental conditions for optimum cognitive functions. The
Society can build on research assessing human cognitive
function in relation to gases deemed to contribute to
lower IEQ, such as carbon dioxide exposure to individuals who would be trained for the rigors of space travel.34
Much of the content from ASHRAE research and in
ASHRAE standards and guidelines can be translated to
extraterrestrial facilities, but further research and work
would need to be done to adapt today's technologies for
the environments that will be encountered in space. Of
particular interest for research and industry guidance
would be the following topics.
Refrigerants and refrigerant cycles. Known refrigerants and refrigeration cycles would need to be reassessed for use in space and extraterrestrial environments, with a heightened focus on refrigerant safety
and maximization of refrigerant system life cycle.
Furthermore, refrigerant system maintenance would
need to consider the competence of crew members and
the required tools and resources to repair such systems,
which may or may not be abundant based on training
and the availability of supplies at various space and
extraterrestrial locations.
Machinery resilience. HVAC equipment for extraterrestrial facilities would need to endure natural elements
that are different from Earth's atmosphere, everything

from near vacuum conditions and high-velocity objects
in deep space to weather disturbances of varying intensities on planets and habitable extraterrestrial bodies
(such as dust storms and thermal tides on Mars).8,35
Air treatment and revitalization. Inhospitable outdoor conditions will require extraterrestrial HVAC systems to ﬁlter and treat air for 100% reuse. Expanding
on past research of gas separation and reuse and air
puriﬁcation for space application will be necessary to
maximize resource reuse on space voyages and planetary colonies and to minimize transport of gases for
human habitat sustainment.36 - 38 Additionally, research
on ultraviolet germicidal irradiation of airstreams may
provide a solution for eradicating organisms, microorganisms and viruses in reused air.39
Systems with simpler maintenance and repair procedures. As more people go to space, people need to
know how to maintain systems without much training.
The availability of expert technicians to maintain and
repair extraterrestrial HVAC systems will vary. Unlike on
Earth, where HVAC mainly provides comfort cooling, the
malfunction of extraterrestrial HVAC systems may result
in loss of life.
Effective heat removal/addition methods and systems for future built environments. In view of the
major differences between environments at different
planets, appropriate methods and systems must be
developed with consideration of each speciﬁc environment to provide adequate heating and cooling for the
built environments in an efﬁcient manner. The presence/absence and type of atmosphere, solar irradiance
and gravity are among the factors that must be considered in developing passive and active strategies for effective heating and cooling of built environments in space.
With the development of refrigerants and equipment
most effective in various extraterrestrial environments
by industry, ASHRAE can build on this work to create
standards for rating the performance of environmental
control systems and components for extraterrestrial and
space applications. Furthermore, ASHRAE can develop
design guides for space and extraterrestrial structures
that address minimal to no energy consumption while
maintaining appropriate conditions for IEQ and resilience against exterior elements.
The built environment in space and on other planets
where resources are limited or minimal will demand
a mindset of using closed-cycle resource processes,
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ASHRAE Journal - July 2020

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