In-situ Habitat Improvement through
Soil Strengthening Payload Experiment
Primary Investigator: Aaron Brown
METROPOLITAN STATE UNIVERSITY OF DENVER | COMMUNITY COLLEGE OF DENVER | UNIVERSITY OF COLORADO
DENVER [Company address]
Payload goals and justification
Problem/need
The human settlement of Mars has been an emerging goal of many companies. However, the
environment of Mars is not harmless, quite the opposite, there are many dangerous elements that we
need to consider when discussing Martian colonization and habitation. The temperature on Mars is one
of the many elements that we will need to plan for when creating Martian habitats with minimum
temperatures reaching nearly 165 K with maximum temperatures of about 270K [1]. Radiation on Mars
is also a concern according to the Mars One FAQ; humans will experience 11 mSv per year of radiation.
This is not an outrageous amount seeing that humans on earth are exposed to 2.4 mSv per year [2]. In
order to prevent more radiation exposure, especially during solar events Mars One has stated, “The
Mars One habitat will be covered by several meters of soil, which provides reliable shielding even
against galactic cosmic rays. Five meters of soil provides the same protection as the Earth's atmosphere- equivalent to 1,000 g/cm2 of shielding” (Mars One, 2013).
This experimental payload will look at reducing the amount of soil that would need to be used to help
with radiation and thermal shielding, as well as provide an increase to impact resistance for the habitat.
The payload will receive a sample of Martian Soil which will be split among three sample containers.
These samples will all be infused with the epoxy resin to create a Martian composite in each container.
Two of the three containers will be housed over sensors, one to test the thermal shielding and one to
test radiation shielding qualities. An impact “ram” will be mounted above one of the samples to test the
samples resistance to impacts. This will allow us to compare plain Martian soil with our composite
material and produce analysis on whether these materials would be more effective and efficient for
future Martian settlements.
Previous Work
Although there has been much work put towards the identification of the chemical and physical
properties of Martian Regolith there has been little work to done in regards to impregnating common
soils with resins to create structural shielding, as this would primarily be done to detract environmental
effects. Soils impregnated with resins or infused with fibrous roots have been studied by groups such as
the U.S. Army and university groups throughout the world; however, studies about strength and
materials physical and mechanical properties are not as significant to the overall tests our payload will
demonstrate.
What we hope the iHISS Payload accomplishes
The iHISS payload will accomplish one of two things, either
A. That a composite made of Martian regolith and epoxy resin can provide better shielding with
less work than moving five meters of regolith over you habitat and provide new and unique
styles of habitat design in the future, or
B. Show that epoxy resin does little to negate the environmental effects of Martian life and lead us
to keep trying new ways to create safer human habitats on Mars.
Working Principle
The Mars One FAQ (Mars One, 2013) states that the radiation levels on Mars range from 15-30 µSieverts
per hour. Therefore, Mars One is planning to cover their expandable habitats with up to 5 meters of
Martian regolith to shield the crew from radiation. Another concern for the settlers will be maintaining a
comfortable temperature inside the habitats; temperatures in the Martian mid-latitudes can range from
-60 to 70 degrees Celsius. (Mars Facts, n.d.) Also, winds can reach 30 meters per second (Mars Facts,
n.d.), creating large dust storms and kicking up small pebbles. It is conceivable then, that the high winds
could slowly erode the protective regolith shielding above the habitats. The MSU Denver SEDS team
believes the Martian regolith shield can be improved by adding a strengthening agent. Such a regolith
composite may better protect the settlers from radiation and impactors as well as provide improved
thermal insulation. This also implies that the Mars One settlers will not need to move as much Martian
regolith to create the habitat shielding. To test this hypothesis the MSU Denver SEDS team has
developed a payload called “In-Situ Habitat Improvement through Soil Strengthening” (iHISS) which will
strengthen samples of Martian regolith using epoxy resin and test the composite’s thermal insulation,
radiation shielding and impact resistance abilities. Each test’s principle is detailed below.
Thermal Insulation Test
The principle behind this test is the diffusion equation of thermal physics:
𝜕𝑇(𝑧,𝑡)
Heating Element
𝜕𝑡
=𝐾
𝜕2 𝑇(𝑧,𝑡)
𝜕𝑧 2
𝑇𝑎 = 𝑇(0, 𝑡)
𝑇𝑏 = 𝑇(𝑑, 𝑡)
Thermocouple
Ta
z=0
𝑇𝐻 − 𝑇𝐿
𝑇𝑀 = 𝑇𝐿 + [
] (𝑉𝑀 − 𝑉𝐿 )
𝑉𝐻 − 𝑉𝐿
z=d
Tb
Interface with PRT
sensor on lander
Temperatures measured by the sensors are
provided by the standard thermocouple
equation (Johnson, 2006):
Where: TM ≡ measured temperature, TL ≡ low
temperature, TH ≡ high temperature, VL ≡ low
voltage, VH ≡ high voltage and VM ≡ measured
voltage at the sensor. TL, TH, VL and VH are
provided by a table for each sensor.
Radiation Shield Test
With this test, we are working to obtain the attenuation coefficient of the regolith and regolith-epoxy
composite. The Beer-Lambert Law allows us to determine this:
𝑑
𝐼(𝑧) = 𝐼0 𝑒 − ∫0
𝛼(𝑧)𝑑𝑧
Where α(z) is the attenuation
coefficient. If the material is
uniform, we get:
γ
UV-B & UV-A
Where z is the thickness of the
sample, I0 is the intensity of the
radiation above the sample and
the intensity below the sample, I, is
obtained from the time-averaged
energy density of the
z=0
γ
1
𝐼
𝛼 = − ln ( )
𝑑
𝐼0
z=d
Electromagnetic waves:
Geiger counter and UV sensor
𝐼=
𝑐𝑛𝜖0
|𝐸|2
2
Where E is the complex amplitude of the electric field, n is the refractive index of the sample, c is the
speed of light in a vacuum and ϵ0 is the vacuum permittivity. The refractive index will be determined via
analog testing in the laboratory on Earth. If we assume uniformity of the electric field, then it is simply
provided by the relation
𝐸=−
Where ΔV is the voltage difference at the sensor.
∆𝑉
𝑑
Impact Resistance Test
fk
Accelerometer
This test involves very simple physics and is
similar to Leeb rebound hardness tests. The
sum of the forces on the impactor is:
𝐹𝛴 = 𝑚(𝑔 + 𝑎) − 𝑓𝑘
mg+ma
Where m is the mass of the impactor, g is the
gravitational acceleration on Mars (about 0.38
of Earth’s), a is the acceleration of the
impactor and fk is the kinetic friction caused by
the impactor’s guide rails (not shown). The
coefficient of kinetic friction will be
determined via analog and functional testing
on Earth. By comparing the post-impact
acceleration with the pre-impact acceleration,
we will obtain a hardness quotient:
𝐻∝
𝑎𝑓
𝑎𝑖
Payload Operations
The iHISS payload (hereafter referred to as "the payload") will compare the thermal insulation, radiation
shielding and impactor resistance of Martian regolith against a regolith-resin composite. The
experiments will be conducted via the following process:
1. After the lander has successfully landed on Mars and completed its characterization period, and
in accordance with the established mission operations schedule, a command will be sent to the
payload to ready its systems.
2. The lander’s Sample Acquisition System (SAS) will be expected to collect some regolith and
deposit the sample into the payload’s trough via the Sample Delivery Door. More than one
scoop may be necessary depending on the scoops available volume, depth of loose regolith in
the sample acquisition area and other factors. The SAS scoop must be able to reach the delivery
port for the payload. This is expected to be possible due to the payload’s proximity to the Water
Extraction Payload.
3. Two methods of sample delivery are currently proposed:
a. The regolith is funneled via the trough into the Equal Volume Sample Cups (EVSC). The
Trough Evacuator System (TAS) will encourage the regolith into the EVSCs and will
ensure the top of each EVSC is clear of extraneous regolith. Then the Sample Release
System (SRS) will release each sample from its EVSC into a test beaker.
b. The regolith is funneled via the trough and its agitators into the Equal Volumetric-flowrate Pipes (EVP) with their valves in the closed position. The valves are opened for a predetermined amount of time to allow the desired sample size to flow into each test
beaker then the valves are closed.
4. The Radiation Shield Test is performed first (duration is about 100 minutes):
a. The Geiger counter is activated and a 60 second reading is taken. A 5 minute wait occurs
then another Geiger counter reading is taken. This reading-wait-reading process is
repeated 3 more times to provide 5 total readings.
b. The UV lamp is activated and the reading-wait-reading process is repeated to obtain 5
new readings.
c. The UV lamp is deactivated.
d. The epoxy resin is impregnated into the regolith sample and the beaker’s agitator is
activated for 5 minutes to promote even distribution.
e. The reading-wait-reading process is repeated to obtain 5 new readings.
f. The UV lamp is reactivated and the reading-wait-reading process is repeated to obtain 5
new readings.
g. The UV lamp and Geiger counter are deactivated.
5. The Thermal Insulation Test is performed next (duration is about 140 minutes):
a. The Top Temperature Sensor (TTS) is activated and takes a 60 second reading to
determine the beaker’s ambient temperature.
b. The heating element is activated and controlled by the Temperature Regulator System
(TRS) to ensure the top-level temperature is maintained at 10 degrees Celsius above
ambient, within a reasonable margin.
c. Once the top-level temperature has been stable for 5 minutes, the Bottom Temperature
Sensor (BTS) is activated and a 60 second temperature reading is gathered.
d. The TRS is then set to maintain a top-level temperature 20 degrees Celsius above
ambient.
e. Again, once the top-level temperature has been stable for 5 minutes, a 60 second
temperature reading is taken from the BTS.
f. The previous two steps are repeated for 30, 40 and 50 degree Celsius temperature
differences above ambient.
g. The heating element is deactivated and the regolith sample is allowed to cool for 1 hour.
h. The epoxy resin is impregnated into the regolith sample and the beaker’s agitator is
activated for 5 minutes to promote even distribution.
i. The TTS takes a 60 second reading to determine the beaker’s ambient temperature.
j. Steps b through f are repeated.
k. The heating element and temperature sensors are deactivated.
6. The Impact Resistance Test is now performed (duration is about 10 minutes):
a. The Impactor System (IS) is activated and completes 5 hardness tests on the regolith
sample, each 1 minute apart.
b. The epoxy resin is impregnated into the regolith sample and the beaker’s agitator is
activated for 5 minutes to promote even distribution.
c. The IS completes 5 hardness tests on the composite, each 1 minute apart.
d. The IS is deactivated.
Additional Radiation Shield, Thermal Insulation and Impact Tests can be performed to validate results
and investigate the composite’s durability. These additional tests will be subject to the mission
operations timetable.
Maturity Estimate
The MSU Denver SEDS team bases its Technology Readiness Level (TRL) assessment of our payload, its
systems, subsystems and components on the definitions provided by NASA in its TRL white paper.
(Mankins, 1995) The TRL of the entire payload system at the time of proposal submission is 3 –
Analytical and experimental critical function and/or characteristic proof-of-concept. However, the TRL of
individual components is higher (5-8) as most are Commercial-Off-The-Shelf (COTS). The TRL of each
system, subsystem and component can be found in the System Hierarchy.
In order for each subsystem to achieve a TRL of 9 by 2016, extensive laboratory testing will be
performed in 2015 by the MSUD SEDS team and participating students and faculty from MSUD, UCD and
CCD. Such tests will include:
1) Investigations into the optimal epoxy resin and the optimal regolith-epoxy ratio
2) Calibration and baseline testing of the Cesium source and UV lamp with the Geiger counter
3) Functional testing of the following subsystems: Sample Delivery Door System, Trough and
Evacuator System, Equal Volume Sample Cups, Equal Volumetric-flow-rate Pipes, Sample
Release System, Temperature Regulator System, Impactor System and Epoxy Injection System
4) Functional testing of the following systems: Sample Delivery System, Radiation Shield Test
System, Thermal Insulation Test System, Impact Resistance Test System and Computer
Processor System
5) Functional testing of the integrated payload.
A timeline of these tests and experiments will be developed upon proposal acceptance.
Works Cited
Johnson, C. D. (2006). Process Control Instrumentation Technology. Upper Saddle River, NJ: Pearson
Education, Inc.
Mankins, J. C. (1995, April 6). Office of Safety and Mission Assurance. Retrieved Octobert 2014, from
NASA Headquarters: http://www.hq.nasa.gov/office/codeq/trl/trl.pdf
Mars Facts. (n.d.). Retrieved October 2014, from NASA Quest:
http://quest.nasa.gov/aero/planetary/mars.html
Mars One. (2013, N/A N/A). How Much Radiation Will the Settlers be Exposed to? Retrieved from Mars
One: http://www.mars-one.com/faq/health-and-ethics/how-much-radiation-will-the-settlersbe-exposed-to