Creating Comfortable Air Conditions in Mars for a Sample Volume Shelter

ME403
Project Report
Creating Comfortable Air Conditions in
Mars for a Sample Volume Shelter
Metin Oktay Balaban
Erdi Çökelekoğlu
Samet Baykul

1. INTRODUCTION
In this project, it is aimed to create a theoretical climate conditions for a sample volume room
- shelter enough for 6 people to live inside. The shelter is designed to be as a cylinder shaped, which
has the radius of 8m and 5m of height. The climate conditions inside the shelter is designed to be
identical with earth conditions in comfort, which is 22°C and %50 relative humidity. The psychrometric
processes and heat transfer phenomena is calculated and necessary operations are shown.
2. SOLUTIONS
OXYGEN
The atmosphere of Mars is about 100 times thinner than Earth's, and it is 95 percent carbon
dioxide. Here is a breakdown of its composition, according to a NASA fact sheet: [1]
Carbon dioxide: 95.32 percent
Nitrogen: 2.7 percent
Argon: 1.6 percent
Oxygen: 0.13 percent
Carbon monoxide: 0.08 percent
Also, minor amounts of: water, nitrogen oxide, neon, hydrogen-deuterium-oxygen, krypton
and xenon.
To solve the one of the main problem on the Mars, Oxygen should be obtained from Martian
surface. There are many researches about that. The one of the most logical is “MOXİE”.
NASA just announced what the Mars 2020 rover will carry to the Martian surface, and one of
them sounds like pure sci-fi: MOXIE, a machine that sucks in carbon dioxide from the Martian
atmosphere and pumps out pure oxygen for use in rocket fuel [3].
In figure 2 shows the Moxie functional block diagram. The CO2 Acquisition and Compression
(CAC) system pulls Martian atmosphere from outside the Rover through a filter and pressurizes it to
~1 atmosphere. The pressurized CO2 gas is then regulated and fed to the Solid Oxide Electrolyze
(SOXE), where it is electrochemically split at the cathode to produce pure O2 at the anode, a
process equivalent to running a fuel cell in reverse.

Figure 1. https://gizmodo.com/nasa-will-make-oxygen-from-co2-on-the-surface-of-mars-
1614018168
Figure 2. https://mars.nasa.gov/mars2020/mission/instruments/moxie/for-scientists/
In addition, the average temperature on the Mars surface is -62.78°C / 220K.
WATER
Another problem is the getting water to obtain moisture air for comfort life condition.
According to, scientists the Mars had water sources in previous ages, but now, there is ice with mineral
forms or ice blocks. It will be mining on the Martian surface. Moreover, there is an article and testing
setup. “A novel concept for extraction of water from the Mars soil in a real-time, open-air process was
demonstrated in a Mars environment chamber. The concept breadboard uses radiative heating to bake
off water from exposed soil contained in a bin. An enclosure, intended to mimic the bottom of a rover,
covers the bin. A fan continuously blows the Mars atmospheric gases through the enclosure to collect

the evolved water while a tiller was used to churn up moist subsurface soil. These initial tests verified
concept feasibility. The sweep gas generated by commercially available muffin fans at 7 Torr was
sufficient to transfer water vapor into a condenser flow loop. The radiative heating, while non-
optimized, heated the soil surface to 60 °C to generate water vapor. A rototiller working through the
soil bin brought sufficient amounts of new moist soil to the heated surface to show an increase in rate
of water extraction.” [4]
HAVING THE ATMOSPHERIC DRY AIR
The generation of dry air will be in sequels. In the first part, the CO2 will be converted into O2
by MOXIE and stored in a room. In a second room, N2, which is present in the martian atmosphere
already as 2.7%, will be filtered and also stored. The stored O2 and N2 will be collected into a third
room, which is the dry air room. Here, their pressure will be increased to 101.325 kPa. The temperature
also will be increased heavily, but with the constant losses, it is not possible to know their
temperatures. Therefore, it will be assumed it will be at -38 °C, which will be used in further
calculations.
VENTILATION
The dry air, which is collected in a room, will be heated and humidified to 22°C and %50 relative
humidity. After that, it will be sent inside the shelter. There is also another ventilation opening to
outside to clean the room inside.
ENERGY
The energy is one of the most critical problem on the Martian conditions. To generate
electricity, the most effective way is the solar energy system. This method is also known and used by
NASA. In an article, “Mars Solar Power”, the environmental challenges to Mars solar array operation
will be discussed and test results of solar cell technology operating under Mars conditions will be
presented, along with modeling of solar cell performance under Mars conditions. The design
implications for advanced solar arrays for future Mars missions is discussed, and an example case, a
Martian polar rover, are analyzed. [5]

INSULATION AND SHIELDING
There are some insulation materials to shield radiation effect and prevent heat loss. To cover
the hemisphere surface, the structure exoskeleton design consisted of a stiff box made of aluminum
honeycomb and carbon composite face sheets lined on the inside with bricks of carbon pacified silica
aerogel. Such aerogel has extremely low density (0.02 g/cm3 ) and a very low thermal conductivity
(0.012 W/mK). [6]
Although, this is useful and tested before, for windows part some new inventions can be more
effective. For example, according to a research which is done in University of Colorado at Boulder, new
gel can increase energy efficiency in skyscrapers and help scientists to build habitats on Mars. It is
almost 100 times lighter than glass. [7]
Also, in order to cover from radiation, the wall at the surface will be covered by a UV shield
and polished aluminum.
3. MATHEMATICAL MODEL
Calculation of the Heat Loss
There are 2 main sources of heat loss from the shelter to the environment. First one is due to
the covnection heat transfer from the top of the shelter and the second one is due to the conduction
from the shelter to the ground. Also, there is a source of heating, which is the irradiation coming
from the sun.
Figure 3 – Heat Transfer from Shelter to the Environment

While calculating the heat loss, there are some assumptions. The temperature of the
atmosphere and the ground is taken as 210K. The inner surfaces of the shelter walls are taken as
295K, same with the temperature we want to keep inside. The irradiation coming from the sun is
taken as 460
𝑊
𝑚2 𝐾
. The martian atmosphere is also neglected as it is very thin, which means the
participating medium is not included.
The maximum irradiation on Mars is 590
𝑊
𝑚2 𝐾
[8]. It changes with the different time of day,
the season and the location. In our calculation, we have taken the radiation flux as 460
𝑊
𝑚2 𝐾
.
It is necessary to shield ourselves from radiation, especially from UV. It is assumed that
the shelter is shielded from UV completely, the shelter is also covered with polished aluminum,
which has the absorptivity of 0.09.
n * λ0 * T = 1 * 0.0 * 5777 = 0 μm K
n * λ1 * T = 1 * 0.4 * 5777 = 2310.8 μm K
F(0) = 0
f(2310.8) = 0.12220, then;
UV band fraction from blackbody at 5777 K is
f(2310.8) – f(0) = 0.12220 – 0 = 0.12220
This fraction of coming irradiation is shielded and directly assumed to be reflected. The
remaining fraction of radiation is 0.8778. Using the polished aluminum surface, the heat gain from
radiation can be calculated as :
Q(rad) = Area * absorptivity * Heat Flux * 0.8778 = 201.062 m^2 * 0.09 * 460 W/m^2*K = 7.308 kW
Next step is to calculate the heat loss from convection. In order to calculate that, the
surface temperature of the shelter wall need to be known. There is also the conduction heat transfer
which needs to be the same with the total net heat from convection and radiation.
Soria-Salinas calculated convective heat transfer coefficient to be approximately 6
𝑊
𝑚2 𝐾
at 4.5 m/s of
wind [9]. Taking that into account, the following results for 216.215K of wall surface temperature:
The surface temperature of the wall, 216.215 K is found by iteration.
Another source of heat loss is by conduction to the ground. Assuming the outer surface
of the wall is at the same temperature with the ground, 210 K, the heat loss due to conduction can
be calculated as:
Close Enough
qconv h Ah Twall Tout  7.498 10
3
 W
qtotal.surface qrad qconv 189.599 W
qcond.surface Ucond Ah Tin Twall  190.088 W

Then the total heat loss from the shelter is :
This amount of heat should be added to the room by heaters.
It is assumed that the ventilated air outside has the same state, state 2. Therefore, the
added enthalpy equals to the lost one. Also, the heat produced by the people inside have been
neglected. Therefore, the total heat addition by mass transfer is zero.
Psychrometric Calculations
It is assumed that in the dry air storage room, the pressure of the air is atmospheric,
101,325 kPa and the temperature of the dry air is -38°C. It is desired to increase the temperature to
22°C. Also, it is desired to have 50% relative humidity, which is 8,5 gw/kga. Then, the following states
are present :
The air consumption for 1 person is 0.5 m^3/h, while for working conditions 3 m^3/h.
Having a good ventilation system, our system is designed for 3 m^3/h. There are 6 people in the
shelter, and the mean density of dry air is 1.2930 m^3/kg (at 0°C). Then the necessary mass of air is:
m.air = 3 * 1.2930 * 6 = 23.274 kg/h
Then, the amount of water that is necessary to add can be calculated by:
m.water = m.air*(w2 – w1) = 198 g/h
State 2
State 1
Area 2  rh height  rh
2
 452.389 m
2

qtotal.ground Ucond Area Tin Tout  461.437 W
Qtotal.loss qtotal.surface qtotal.ground 651.036 W
w1 0 w2 0.0085
kg w
kg a

T2 273 22( )K
T1 273 38( )K
h2 43500
J
kg

h1 37976
J
kg


It is also necessary to find that what is the temperature of the water that is being added.
It can be calculated from the enthalpy of the water that is being added. This can be calculated as :
So hw = 2663 kJ/kg. From the thermodynamics tables, it can be seen that the temperature
of the water steam is 92 °C.
4. CONCLUSION & DISCUSSION
In this project obtain how suitable shelter conditions for humans. The shelter is
kept at 22°C and %50 relative humidity.
The set up of our shelter is that the shelter is buried in the ground as a cylinder,
with top of the shelter is at the surface of the ground. We have assumed certain
environmental conditions, such as 210K of air and ground temperature, 460 W/m^2*K
irradiation etc. This assumptions are valid for the martian conditions for certain times. With
the different environmental conditions, different results may be get in order to keep the
shelter air conditions at desired levels.
One of the biggest discussion points is, while the heat is added to our shelter with
our current set up, such as absorptivity of the walls and low conductivity, there may actually
be need to cooling rather than heating with little changes, such as increasing the
absorptivity.
There are also many other assumptions that have been made in psychrometric
applications and machine set-up. All of them are highlighted in their respective sections.
Some parts of the project are also needs confirmation in real world, such as MOXIE.
Converting CO2 to O2 is not an easy process, but it has been assumed that it works.
Overall, even though there are many ways to improve in the project, the
fundamental steps have been discussed and shown in order to create a comfortable
environment in a shelter in mars conditions.
hw
mdotair h2 h1 
mdotair w2 w1  3600
2.663 10
3

m
2
s
2


REFERENCES
[1] https://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html
[2] https://mars.nasa.gov/allaboutmars/facts/#?c=inspace&s=distance
[3] https://mars.nasa.gov/mars2020/mission/instruments/moxie/for-scientists/
[4] https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160010258.pdf
[5] https://ntrs.nasa.gov/search.jsp?R=20040191326
[6] Arnau Miro Jane, Study of advanced materials for thermal insulation in the inner Solar System,
Department of Aerospace Engineering ETSEIAT – UPC, Sept. 2014.
[7] University of Colorado at Boulder. "From windows to Mars: Scientists debut super-insulating gel."
ScienceDaily,13 August 2018.
[8] Appelbaum, J., Flood, D.J., Solar Radiation on Mars, National Aeronautics and Space
Administration (NASA), 1989
[9] Soria-Salinas, A. Convective Heat Transfer Measurements at the Martian Surface, 2015

Creating Comfortable Air Conditions in Mars for a Sample Volume Shelter

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