第1１回月惑星に社会を作るための勉強会
2021年５月2６日

第10回（4月23日）「月面居住施設建設と３Dプリント技術」発表に関するフィードバックに基づく追加情報
鶴巻 崇

1．南極付近の地形と日照率
2. 光ファイバーによる彩光
3. 内圧
4. 放射線

1．南極付近の地形と日照率

月の海の地形ー

南極の地形はこれとは対比的に起伏が激しいクラビウス・クレーター（直径225km)

南極から2000kmほど北にあるクラビウスクレーターの北側の縁から南極へ向かってみたところ

ニュートン・クレーター（直径76km)

ニュートン・クレーター

ニュートン・クレーター

南極から750kmほど北にあるニュートンクレーターの様子 : 起伏の大きい地形を考慮した施工計画が重要である。

出典：ESA(Jorge Mañes Rubio)

極地方の日照率に関して考慮すべき点

シャックルトンクレータの縁と、そこから約10km離れた尾根の上の場所を互いに行き来出来るという前提がでトータルで94％の日照率は考えられる。
（つまり一方が影の時、もう一方の方に移れていれば、年にトータルで94％日照率が達成される）
二点間は10km、さらに尾根とはいえ起伏があり、簡単に行き来はできない。
極の日照率が良い場所というのは、
よくて85％程度と考えておいた方が良い。
長期日照域の日照率について、パネルを10m程度立ち上げるという前提条件が考慮されていない傾向が見受けられる。今後の計画で注意が必要。

m

10k

出典：ESA

２．
光ファイバーによる彩光

太陽追尾システム
建築・船舶へ応用可能光ファイバーの敷設距離によって光量の減衰が大きいので注意mbination with an inflatable deployable multilayer shell, encompass a pressurized
ESA,SOM,MIT - Lunar Habitat 2020
ume of 698.29 m3 when deployed.
Windows

Moon Villa
CDF Study Report: CDF-202(A) – Issue
September 20
page 24 of 1

光ファイバーによる太陽光の彩光は可能であるが、外部を視認できることの重要性も強調されるべきであろう。

Figure 3-6: Habitat in x-ray view300から500日の長期滞在を目標とするとき精神的にも外部が確認できることの意義は大きいはずである。
また、外部で活動するクルーが内部と視覚コミュニケーションを取る上でも有用であると考えられる。

publishing.org/journal/rsta Phil. Trans. R. Soc. A 379: 20200142

ESAによる3Dプリント月面居住施設

Vacuum（真空）100000N / m²

Downloaded from https://royalsocietypublishing.org/ on 05 April 20213．
内圧

Downloaded from https://royalsocietypublishing.org/ on 05 April 2021.....................................................

brought sequentially into position under the
Vacuumon for slow annealing and cooling to avoid
A hard vacuum surrounds the Moon. This will preclude the use ofand the mould refilled.
certain materials that may not be stable if exposed under such
真空中に建造物を作り、内部を約1気圧（101hPa)の空気で満たすと１平方メートルあたり100000Nの荷重がインテリアの壁において外側に向かって働くことになる。
Three years of robotic
preparationof theEnvironmental Conditions
conditions. Outgassing materials and structures, e.g., hydraulic
これに抗する構造は、月面に考案されている居住施設の個々により、大きく異なる。
which can be expected to last for millennia,
systems, have to be avoided. A lunar structure will not be sub構造システムをなるべく軽減するため、酸素分圧を上げて内圧を約70kPaとする考え方を採用する施設設計もあるので数値設定の裏付けは重要である。
Gravityjected to any kind of wind loads.
stone construction. One goal of returning toOn the Moon, gravity is 1 / 6 g. That means a structure will have,term human habitation off the Earth.
in gross terms, six times the weight bearing capacity on the Moon
Dust
PV electric power might be implemented
as on Earth; the structural dead loads will be reduced by 5/6
The lunar surface has a layer of fine particles that is easily disiftheconversion efficiency of AM0 solar r
compared to the ones on Earth. Mass-based rather than weightturbed and placed into suspension. These particles cling to all
ESAの３Dプリント月面居住施設では金属とナイロンを原料とする15~20センチの厚さがある多層強化繊維の使用が膜構造として採用さ40人を収容する大型建物である本計画では、
強化繊維膜を地球から運搬する手間を省き、代わりにレゴリスの重量をおもしにして１平方メートルあたり
orientation
convert 1/3 of the available sunlbased criteria are recommended to maximize the utilityof consurfaces, are highly abrasive, and pose serious challenges in the
Figure1. Large for
enclosedstanding
after millennia.
(a) and (b) the
Treasuryof Atreus in Mycenae,
and (c)cepts
developed
lunarstructures
structuralstill
designBenaroya
et al. 2002.
れる。100kPaの内圧により1平方メートルあたり100000Nとなる荷重に対しては繊維の引張力で抵抗する。
70000Nの内圧に抵抗させるという構造コンセプトを採用している。
an average power of 0.09 kWh h−1 m−2 for hutilityof construction
equipment
andthethe operation and maintePantheon in Rome. (Online version in colour.)to that from the reflector. Additional heatin
３Dプリントされるレゴリスと強化繊維の間には３０cmの緩衝帯が設けられており、この内圧はレゴリスの外壁に到達しないように設計されレゴリスの重しだけで１平方メートルあたり70000Nの内圧に抵抗するので２０mの厚さの壁が必要になっnance of airlocks Benaroya and Ettouney 1992a,b. てくる。
Internal Air Pressurization
could be used to triple production rate, reduている。
気密性を確保するために採用されているのは０.１mmという極薄のプラスチックシートで、この薄い材料は引張力による抵抗力がほとんない。
The lunar structure is in fact a life-supporting closed environMoonquakes
つまり、レゴリスの外壁はメテオロイドと放射線の遮蔽に専念する。
ment. Generally, the optimum habitat internal pressure is Earth’s
is little or no seismic activity on the Moon. Therefore, lunar
From “Pantheon habitat made from regolith with a focusing solarThere
reflector”
また、多層強化繊維は分厚く強度の高い材料なので比較的小さな4人収容の施設に必要な膜でも地球で打ち上げの際の重量は数トンのatmosphericfrom
pressure,
but
the pressure
the
Earth
is plastic
film todifferential
sealsmallbetween
gaps University
betweenthe
to USA)
prevent
air include
leakingearthquakelike
out.
structuraldesignwill notloads.
by needed
Nick Wolf and
Roger
Angel (Steward
Observatory,of blocks
Arizona,extravehicularEVA issuits
and the habitatbe
重さになる。
The tension activity
in the plastic
proportional
to the should
gap width.
https://ui.adsabs.harvard.edu/abs/2021RSPTA.37900142W/abstract
minimized for safety reasons. Much like scuba diving, the danTemperature
The density of regolith is approximately 1.7 and of cast blocks
3.0. Supposing an atmosphericgerous aspect of changing pressures is the formation and expanTemperatures
surface
rapidly change from approxipressure
of
70
kPa
(following
Ruess)
andallowing
forthereducedgravity on
onthethelunarMoon,
1/6 thatsion of gas bubbles in the blood and lungs. Historical internal
The light focused as shown in figure 2 musmately 100 to −150° C in the transition between day and night,of Earth,a minimum
25 ranged
m of regolithor 15pressures
usedfor NASAthickness
programs of
havefrom 34.5
kPam of the denser cast blocks is needed.
which occurs in roughly two-week cycles.
above the structure and then distributed to t
2
From“Structure
Designofa
Lunar
Habitat”
on the willMoon
101.4 nearkPa 14.7
psi; pole, where there are deposits of water
assumebe tolocateda lunar5 psi;We21,
300 kg/them habitat
15~20センチの厚さがある多層強化繊維
light through a 25 m long light pipe passing
byF.600
Ruess,
Benaroyatoto providea H.
livableenvironment
for the62,kg/ mJ.2 Schaenzlin,
andvolatiles
replaceandatmosphericgas, and sites
can be found with near permanent solar
内圧に対して 繊維の引張力で抵抗
https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.503.9275&rep=rep1&type=pdf
a giant fused silica fibre, but this would be
Structural
Requirements
astronauts.
illumination. Sunlight will be brought in through a small oculus
via a mirror
which follows the
The habitat module pressure and the pressure used in spaceweigh 73 tons. But a hollow pipe can be madsun as it moves around the horizon once a month.
Building a structureon the Moon results in many different and
論文内では70kPaの内圧の採用の根拠としsuits for EVA influence one another. EVA productivity increases
highly reflective walls with a multilayer diadditional
requirements
to be fulfilledby the structure.
In orderget pressuresenough because
sunlightthetogloves
grow become
crops throughanoculus smallenoughthattobea sealedて“Structure
DesignofhaveLunar
Habitat”がwith theuse of to
lower
more
Thick material with very high tensile strengthcommercially to cover the spectral range ofwith aElrod
transparent
pressure
window,
thepressures
light mustbe focused
as it passes through the window
flexible
1995. At
the sametime, lowincrease
引用されている。
Structural
Adequacy
ranging from 0° to 45°, have a reflectivity gr（内圧に対して、繊維の引っ張り強さで抵抗）
thebefore
fire hazard,
and lower
voicetheandhabitat
cough mechanism
effectivespreadingout onto
floor.
参照として航空機の客室の空気全圧は80kPa
The structure must sustain all dead and live loads with an accept-Airtightto be obtainable
seal: in a coating tailored for incid
ness for astronauts. It is assumed that the actual habitat pressureに対し、酸素分圧は16kPaである。
able degreeof safety. A minimum of structural material is desired.
will be around 69 kPa 10 psi; 42, 600 kg/ m2. The enclosure
range thickof 450–650
nm. (plastic sheet)
0.1mm
mylar
本計画においてレゴリスの厚さを20mに軽減す
The use of lightweighthigh stiffness to weight ratio materials is
structure must contain this pressure, and must be designed to be
A typical ray of light passing down thenecessary.
るために空気全圧を70kPaとしているが、
failsafe against catastrophic and other decompression.
thus lose in all 10% of its energy. The heati
酸素分圧をこれに対して調節する前提であるとThe large mirror above the oculus will be shaped as an off-axis
sectionofaparaboloid,shownin
100 kW. Spread over the 100 m2 area of theMaterial Properties
Radiation/Shielding
考えられる。
figure 2. We consider here an example in which sunlight is collectedovercircularaperturematerials
anddensity than sunlight warming the Earth. T
Properties
foralunar
construction
should include highA prime consideration in the design is that the structure must be
これはNASA
CR-2004-208941”Advanced
reflected
down
to
the
focus
in
a
60°
cone
symmetricabout
theverticalaxis.
Ray
tracingshows
that
the remaining 90% of the energy absorbed bstrength,ductility,
durability,
stiffness,
and
tear
and
puncture
reable to shield against the types of hazards found on the lunar
Life
Supportsistance,
low solar
thermalexpansion. The stability ofa perfectly
shapedmirror withthis geometry
wouldform animage
oftogether
the 1/2with
degreedisc
temperature, in order to maintain its very hi
surface:Continuous
solar/cosmic
radiation,
meteoroid
impacts,theseimperfections
mechanicalproperties
and lowleakage areimportant.
extremetemperature,with avariations
diameterin0.013
that ofand
theradiation.
entrance aperture. In practice,inassemblyandBaseline
ValuesandAssumptions
DocuThe 1 MW of sunlight exiting the pipe wil
There arewill
two leadkindstoof aincoming
radiation
thesuppose
lunar sur-this ment”に環境を維持する値として酸素分
pointing
larger focus.
Weon
will
to be twice the ideal disc diameter,area at the normal full sunlight intensity. B
Maintenanceface:radiation andionizingTheradiation.
These par-of sunlighti.e. Electromagnetic
0.026 of the entrance
aperture.
concentration
averaged across 全圧は48.0～102.7kPa
this disc is
圧は18.0～23.1kPa、
time, a means to simulate day and night will
ticles interact with 2the Moon in different ways, resulting inUpkeep, inspection, maintenance, and repairs have to be kept at a
1400 × 1/(0.026) .
between several crops by optical or mechan
でノミナル70.3kPaとされていることに矛盾し
penetration depths that vary from micrometers to meters. Any
minimum.
The initial use of the concentrator will be to melt regolith
into building blocks. In order toseveral days of continuous darkness each m
ない。
AEROSPACE
ENGINEERING
calculate the solar power density at the focus, we assume theJOURNAL
mirror isOF
coatedas needed
for habitat © ASCE / JULY 2006 / 135
battery powered LED lighting will likely behttps://core.ac.uk/download/
illumination, reflecting the wavelength range 450–650 nm andrejecting the remaining spectrum,
far lower light level, as on very cloudy days
pdf/4947189.pdf
to eliminate unnecessary heating when the light is used later to grow crops. Such a reflector may
be made with a high efficiency multilayer dielectric coating. The solar power incident in this−2 .weight against
Regolithasis 700 kW mspectral range is approximately 500 W m−2 , thus the power density at the focus
Regolith for meteoroid and solar radiation
Here we consider a concept for a habitat ofRegolith placed at this focus to be melted into blocks may be heated to a temperature
limitedoutwards atmospheric(2000 m2 ) over living quarters of the same arby the balance of absorbed sunlight energy and thermal losses. Radiative losses
will
completelypressure
この２つの月居住施設の参照例において内圧
needed to balance atmospheric pressure, anddominate, since the blocks will be cast in moulds of ceramic fibre, which is a good thermal

Lunar Environment

太陽光集光リフレクターを装備したレゴリスより作られるパンテノン居住施設

3. Solar concentrator and regolith block casting(a) Getting in and distributing the light

th

m（
2５
〜 ity
５ s
１ en
d

Atmospheric pressure（内圧）：100kPa

4. Concept for a 50 m diameter hab

s

es

kn

ic

(b) Structural and thermal design

n
pe

de

ds

に対する構造の考えはまったく異なる。

on

論文内では 70kPaの内圧の採用の根拠として“Structure Design of a Lunar Habitat”が引用されている。

Multi-layered fabricCorbelled regolith block2m

70000N / m²

Atmospheric pressure（内圧）：70kPaAnalysis of

Nick Wolf and Roger Angel
Steward Observatory, University of Arizona, USA

ttps://royalsocietypublishing.org/ on 05 April 2021

Pantheon habitat made from regolith,with a focusing solar reflector

azimuth bearing
light pipe
earth view mirror

pressure window

regolith

regolithliving quarters

bedrock
50 mairlock doors and window

Figure 4. Habitat with 50 m diameter growing area.

area at normal solar intensity is accomplished by use of a reflector of the type shown in figure 2,
also 50 m in diameter, to collect the same area of sunlight. The focal spot will have a power in the
450–650 nm band of 1 MW, and a diameter of 1.3 m, 0.026 of the 50 m entrance aperture.
In broad brush outline, the structure we consider shown in figure 4 resembles the Atreus
Treasury in being built as a cone of blocks under compression from soil above. In fact, the weightPantheon, Rome (126 AD)

50m

35m

90m

Existing problems- High cost of transport (to bring resources from Earth to Moon)- Requirement of advanced material processing

Proposal of this project- Using In-situ resources- Minimal manufacturing process (primitive constitution method)- Building food supply facility

Key Structure ConceptThis project adopts one of the most primitive structure systems older than voussoir arch

Example of Corbelled dome

Treasury of Atreus (1250 BC)

Corbelled Arch
3000 B.C.

due to delays in developing commercial vehicles needed to fly people to orbit.
Fortunately, at the same time NASA decided to test the technology on ISS and planned
to send the BA-330 into orbit. However, first a smaller version, called BEAM, needed to
be tested. RD[74] BEAM (Figure 13-4), of 16 m3 pressurised volume, was launched into
orbit in 2016 and was attached to ISS. BEAM has been successfully fulfilling its purpose
relyingon advanced
fabricto Notdate, andwill remain
in service until
2028. technology

Vacuum
150 ~ 200mm thick multilayer fabric made ofnylon and metal fibre
Thick material with very high tensile strength

ISS BEAM

Figure 13-4: BEAM module (Source: abcnews)

In Europe, ESA has studied inflatables for space applications with its industry partners.
Some of the projects are Inflatable Capture Mechanism (ICM), Inflatable manned
module (IMOD), Flexible Expandable RegolithCommercial
Module (FLECS) and SpaceHaven.
for meteoroid and solar radiation

13.1 Challenges with Human-Rated Inflatables
The main benefits of using an inflatable space habitat is its ability to package thestructure into various compact shapes for launch and that way save a lot of volume
during transport. In addition, inflatables ensure a significant mass reduction, whencompared to traditional rigid modules, in three ways: (1) the use of very high specificstrength filamentary materials; (2) reduced design loads since the design is driven by inspace loads following deployment, instead of loads induced during launch, which are
typically higher; and (3) reductionin the massof the launch shroud and launch system
Multi-layered
fabricdue to the compactness of the packaged inflatable structure. RD[76] However, at the
moment, the use of fibrous inflatable structures in space applications is approachedwith a lot of hesitation due to the of use non-traditional materials, non-traditional
manufacturing techniques, and load paths in structures that are not precisely defined.
Although high-performance fibrous components such as straps, cords, and fabrics
possess extremely high specific strengths, their use is challenging because they arehighly nonlinear, subject to creep, and subject to imperfections created during the
Various lunar habitat project based on inflatable membrane technology
fabrication process. In order to make the most efficient use of the specific properties andbenefits of these materials structural concepts must be developed with rationality and100000N / m²
Atmospheric pressure(100kPa)

But this project to be away from advanced fabrictechnology due to limitation of rocket payload

Key Structure ConceptKey Structure Concept
Not relying on advanced fabric technology

20m

Regolith as weight against outwards
atmospheric pressure

Airtight seal:
0.1mm thick mylar (plastic sheet)

Atmospheric pressure(69kPa)2m
Corbelled regolith block

70000N / m²
Atmospheric pressure：70kPaReason:Productivity of extravehicular activity
increases with the use of lower pressure
because the gloves become more flexible.

50m

25m

35m

25m

50m
90m

Construction Sequence 1- Transport a solar concentrator with 50m diameter- Produce regolith block by solar sintering (melting method)- Production process will take 3 years

Location: Lunar pole
Deposit of water & volatiles
Permanganate solar illuminations
Light weight mirror system brought from Earth

50m

Honeycomb backed mirror panel

Carbon fibre structure frame

Regolith block produced in ceramic fibre mould at 1600 °C

Construction Sequence 2- Find bedrock- Excavate bedrock and make surface good to start piling up regolith block- The pit to be sealed against air leakage

Lunar digger

Perimeter bedrock wall to resist the outward thrust of sloping
walls of the cone roof.
Bedrock

50m

Construction Sequence 3- Living quarters built with vaulted ceiling

Regolith block

Living quarters

Construction Sequence 4- Entrance tunnel and airlock built

Regolith

２0m
２m

Regolith blockConstruction Sequence 5- Pressure window installed on the top of the cone roof
Window flange to resist outwards air pressure

Pressure window to be set(1.3m fused quartz pressure window)(Considering degradation issue under radiation)

Construction Sequence 6- 25m tall light path built

5m
Airtight seal:
0.1mm thick mylar (plastic sheet)40°

Spiral route for mining vehicle
carrying up regolith25mConstruction Sequence 7- Light pipe installed (1.3m diameter)- Light pipe with dielectric coated mirror(fused silica fibre will be too heavy (73 tons))

1.3m

Construction Sequence 8- Solar concentrator 50m diameter installed- Mirror with multilayer dielectric coating will reflect only
the wavelength range 450nm - 600 nm and reject the remaining
spectrum (eliminate solar radiation)

ransmitted in theticles. In some
(infrared

ma rays are notrectly withnegative effects

an also bee systems.

uces

alled

e from theh empty spaceentists haveual “personality.”

Figure 3: The Electromagnetic Spectrum

wavelength,
more energetic
the radiation
the greater
theMultilayer the
dielectriccoat onlyreflectand
visiblespectrumpotential
for biologicalharm.450nm - 600 nm)(the wavelengthrange

f particles (callede highest energy

e versa. The fullalled thehe shorter the

On Earth we are protected from much of the electromagnetic
radiation that comes from space by Earth’s atmosphere andmagnetic field. Most radiation is unable to reach the surface of10Construction Sequence 9- Installing airtight seal all over the cone ceiling- Planting trees- 2000 m² floor area (1st floor) for crops feeding 40 or more people- 2000 m² floor area (Ground floor) for Living quarters

Azimuth bearing (follow solar movement)

Scale comparison with 3D printed ESA Lunar Habitat

NASA

Space Radiation

4．放射線

Chapter 1

Radiation
What Is Radiation?
Radiation is a form of energy that is emitted or transmitted in theform of rays, electromagnetic waves, and/or particles. In somecases, radiation can be seen (visible light) or felt (infrared
radiation), while other forms like x-rays and gamma rays are notvisible and can only be observed directly or indirectly withspecial equipment. Although radiation can have negative effects
both on biological and mechanical systems, it can also be
carefully used to learn more about each of those systems.
The motion of electrically charged particles produces
electromagnetic waves. These waves are also called“electromagnetic radiation” because they radiate from the

Figure 3: The Electromagnetic Spectrum

4
Lunar Regolith Usage

Necessary thickness of regolith wall as radiation shield

Regolith protection would be in the form of a shield or blanket of regolith covering
the habitat with each threat requiring a different blanket thickness for adequate/
acceptable protection.

and manufacturing will succeed in space if only entrepreneurs areturned loose and perhaps assisted with federal money or incentives. 3He helium3 is a very rare helium isotope mining could
solve energy problems for generations once nuclear fusion technology becomes practical. And the demand for trips into space isthere, so entrepreneurs have started to provide the supplyBenaroya 1998; O’Dale 1994.
Steppingstone to Mars

Radiation:

Lifting heavy spacecraft and fuel out of the Earth’s gravity isexpensive. Spacecraft assembled and provisioned on the Moon
could escape its lower gravity using far less energy and thus far
less cost. With the experience and knowledge gained on theMoon, we will then be ready to take the next steps of space
exploration: Human missions to Mars and beyond Dubbink
2001.

A shield to protect against radiation exposure in a lunar habitat must reduce crew
exposure levels from lunar radiation sources (GCR & Solar) to acceptable levels. A
layer/shield of regolith accomplishes this reduction by increasing the mass/materiala radiation source must traverse to reach the crew. The more material a radiation
source passes through the more its radiation energies are reduced or stopped by its
particles interacting with the material. Specifically, solar wind particles have such
low energies (keV) that they are stopped in less than a micrometer of regolith while
Lunar Environment
solar event particles will pass through ~50-100 centimeters of regolith before being
significantly mitigated (See Figure 4). In addition, heavy nuclei GCR particles are
Environmental Conditions
stopped by ~10 centimeters of regolith while all other GCR (GeV) particles are
Gravity
stopped by 1000g/cm3 of material which equates to 5 meters of lunar regolith
3
On the Moon, gravity is 1 / 6 g. That means a structure will have,(2g/cm ) or the Earth’s atmosphere [Heiken 1991]. However since NASA’s current
in gross terms, six times the weight bearing capacity on the Moon
acceptable limit for radiation exposure is 25 rem/month not zero, less than 5 meters
as on Earth; the structural dead loads will be reduced by 5/6of regolith shielding (i.e., 10cmAL- - Standard Space Vehicle Shielding = 13cmregolith ) would
compared to the ones on Earth. Mass-based rather than weightbe acceptable GCR protection. Therefore based on the maximum protection
based criteria are recommended to maximize the utility of concepts developed for lunar structural design Benaroya et al. 2002.
required, as described above, 1–2 meters of regolith appears to be adequate for
effective shielding of a lunar habitat to avoid radiation sickness in the crew
Internal Air Pressurization[Silberberg 1988].
The lunar structure is in fact a life-supporting closed environNancy J. Lindsey,
ment. Generally, the optimum habitat internal pressure is Earth’s
International
Lunar
Conference
2003
Figure 4: 5-cm Body Depth Dosage Comparison

Reference:
for Three Large Flares [Nealy 1988][Silberberg 1985]Silberberg, R. et al, “Radiation Transport of Cosmic
FlareShieldPredicted
Ray Nuclei in Lunar
Date
Thickness (cm) Dose (rem)Material and Radiation Doses,” Lunar Bases and Space Activities of the
1956
50
13.30
21st Century, NASA100
5.55
Symposium Publication(Houston,
Texas:
Lunar
1960
50
3.59 and Planetary Institute,
100
0.431985).
1972

50

Note: 10025 rem = 250mSv

Thermal:

0.56
0.07

atmospheric pressure, but the pressure differential between theextravehicular activity EVA suits and the habitat should be
minimized for safety reasons. Much like scuba diving, the dangerous aspect of changing pressures is the formation and expansion of gas bubbles in the blood and lungs. Historical internalpressures used for NASA programs have ranged from 34.5 kPa
5 psi; 21, 300 kg/ m2 on the Moon to 101.4 kPa 14.7 psi;
62, 600 kg/ m2 to provide a livable environment for the
astronauts.
The habitat module pressure and the pressure used in space
suits for EVA influence one another. EVA productivity increases
with the use of lower pressures because the gloves become more
flexible Elrod 1995. At the same time, low pressures increase
the fire hazard, and lower voice and cough mechanism effectiveness for astronauts. It is assumed that the actual habitat pressure
will be around 69 kPa 10 psi; 42, 600 kg/ m2. The enclosure
structure must contain this pressure, and must be designed to be
failsafe against catastrophic and other decompression.

A shield to protect against the extreme thermal variations on the lunar surface
1 -maintain2m thickregolithwall notto exceed
250mSV a month Radiation/Shielding
must
the lunar
habitat structure
at a relatively
constant
and reasonable
A prime consideration in the design is that the structure must be
temperature so that an internal habitat Thermal Control System (TCS) can beable to shield against the types of hazards found on the lunar
optimally designed. A regolith layer/shield accomplishes this because regolithsurface: Continuous solar/cosmic radiation, meteoroid impacts,
extreme variations in temperature, and radiation.
has low thermal conductivity (2-4 x 10-6 W/cm2 [Heiken 1991]), which makes it

There are two kinds of incoming radiation on the lunar surface: Electromagnetic radiation and ionizing radiation. These particles interact with the Moon in different ways, resulting in
penetration depths that vary from micrometers to meters. Anykind of lunar surface habitat will have to be protected from threedifferent kinds of ionizing radiation in space: Solar wind, solar
cosmic rays, and galactic cosmic radiation.
Meteoroids are naturally occurring small solid bodies travelingthrough space at very high speeds.
Most likely, a layer of compacted regolith will be placed atop
the structure for protection against all of those hazards. It provides shielding against most micrometeoroid impacts because therelatively dense and heavy regolith absorbs the kinetic energy. It
appears that at least 2.5 m of regolith cover would be required tokeep the annual dose of radiation at 5 rem, which is the allowablelevel for radiation workers. In addition, it greatly reduces theeffects of the extreme temperature cycles. The mass of regolith isabout 1.7 g / cm3. With an assumed regolith cover of 3 m, theresulting dead load on the structure will be 5,100 kg/ m2.
Other shielding concepts include passive bulk shielding withmaterial other than regolith, electromagnetic shielding, electrostatic shielding, and chemical radioprotection.
VacuumA hard vacuum surrounds the Moon. This will preclude the use ofcertain materials that may not be stable if exposed under suchconditions. Outgassing materials and structures, e.g., hydraulicsystems, have to be avoided. A lunar structure will not be subjected to any kind of wind loads.
Dust
The lunar surface has a layer of fine particles that is easily disturbed and placed into suspension. These particles cling to all
surfaces, are highly abrasive, and pose serious challenges in theutility of construction equipment and the operation and maintenance of airlocks Benaroya and Ettouney 1992a,b.
Moonquakes
There is little or no seismic activity on the Moon. Therefore, lunar
structural design will not include earthquakelike loads.
Temperature
Temperatures on the lunar surface rapidly change from approximately 100 to −150° C in the transition between day and night,
which occurs in roughly two-week cycles.
Structural Requirements
Building a structure on the Moon results in many different andadditional requirements that have to be fulfilled by the structure.
Structural Adequacy
The structure must sustain all dead and live loads with an acceptable degree of safety. A minimum of structural material is desired.
The use of lightweight high stiffness to weight ratio materials isnecessary.
Material Properties
Properties for lunar construction materials should include highstrength, ductility, durability, stiffness, and tear and puncture resistance, together with low thermal expansion. The stability ofthese mechanical properties and low leakage are important.
Maintenance
Ruess F 2006
Upkeep,inspection,design
maintenance,
repairs
have to be kept at a
Structuralof aandlunar
habitatminimum.
JOURNAL OF AEROSPACE ENGINEERING © ASCE / JULY 2006 / 135

Note:
5 rem = 50mSv
This is a 1/5 of the allowancedefined by NASA and ESA

2.5m thick regolith wall not
to exceed 50 mSV a year

Table 3: Radiation penetration and exposure limits.

Moon Village
CDF Study Report: CDF-202(A) – Issue 1.1
September 2020
page 127 of 185

the ground floor of the habitat. This approach will give a slight overestimation of the
GCRs dose due to the fact that the crew do not spend the whole year in the top floor of
the habitat. However, in this study EVAs, which would provide an increased dose rate,
have not been considered.
BFO: Blood Forming Organ
To estimate the minimum amount of shielding material to be placed in the habitat, thedose limits provided by ESA and presented in Table 10-1 were used: the BFO dose
equivalent may not exceed 500 mSv/year and 250 mSv/30 days. With thesedose limits the career of the astronaut will be limited to two years and the average lifetime loss can be expected to be more than 10 years, as reported in Table 10-2. A safer
and recommended shielding configuration is therefore more in line with what is
proposed in Configuration 3.
Configuration 1:
Simulations on Configuration 1 are performed on the habitat model without any
additional shielding. Row 1 Table 10-5 shows that the BFO average dose, of 720 mSv, at
the ground floor during this SPE far exceeds the yearly BFO dose limits stated by ESA,
Table 10-1, even without taking the radiation dose due to the GCRs into account. The
total annual BFO average dose equivalent of 994 mSv is close to the total career dose of1000 mSv for ESA astronauts, see Table 10-1. Even when considering the BFO Average
dose equivalent from the Oct 1989 SPE, of 241 mSv, the annual total dose still exceeds
the 500 mSv/year limit. From these simulation results, it can be concluded that the
habitat needs additional radiation shielding.

Table 3 compares the specific exposure limits between the
Table 4: Missions and radiation dose.

general public and astronauts. Astronauts who spend threemonths in the ISS will be subjected to over three times the
maximum recommended dosage of radiation for one year.
Table 4 compares and contrasts various missions and their

The difference between the estimated BFO average dose equivalent, in Table 10-5, due
to GCRs at the ground floor, of 225 mSv/year, and the top floor, of 274 mSv/year, shows
the additional shielding that is due to the material, such as storage, which is located in
the ground floor and the additional shielding that the upper floors provides for the
ground floor.

durations with the observed radiation dose.
Crews aboard the Space Station receive an average of 80 mSv
for a six-month stay at solar maximum (the time period with the
maximum number of sunspots and a maximum solar magnetic
field to deflect the particles) and an average of 160 mSv for a sixmonth stay at solar minimum (the period with the minimum
number of sunspots and a minimum solar magnetic field).
24

NASA
Space Radiation ebook

The simulation results from configuration 1 clearly show that additional radiation
shielding is needed. Using additional habitat material, such as extra layers of inflatables,
water, or lunar regolith, could solve the issue. The disadvantage of adding additional
fabric layers is the additional launch mass, costs, and risks. It is therefore recommended
to use the materials already present on the Moon, such as the lunar regolith or rocks, toshield the habitat. For this study, it has not been assumed that any larger amounts ofwater are available for extraction from the Moon and the water used for the radiation
shielding has to been launched from Earth. The water that would be needed for the life
support of the crew could be stored in a tank located in the roof of the habitat or the
shelter and hence act as additional radiation shielding. The amount of water needed forthe minimum shielding, around 8 tons for configuration 2, has been chosen in order tobe in agreement with the amount needed for life support, see Chapter Life Support.
Configuration 2:

Radiation exposure limit for astronauts
250 mSv (30 days)
500 mSv (a year)

The minimum shielding required to stay below the BFO average dose equivalent limitsof 500 mSv/year and 250 mSv/30 days are listed in Table 10-3. For the surfaces coveredby the inflatables a minimum of 2 cm of sintered lunar regolith or 4 cm of loose regolith,
is needed. With this amount of shielding the BFO average dose equivalent from GCRs in
the top floor of the habitat will reach 248 mSv/year, see Table 10-3 column 3. The

ESA Concurrent Design Facility Report (September 2020)
ESA UNCLASSIFIED – Releasable to the Public

NASAとESAによる宇宙飛行士の月間の被曝上限は250ミリシーベルトと定められている。
これは一般の人に対する 被曝上限 1ミリシーベルト に比べるとかなり大きい値であることが分かる。NASAのシンポジウムで発表された論文に、年間250ミリシーベルトの被曝を超えないために１から２メートルの厚さのレゴリスが必要と概算している論文がある。
ただし、遮蔽壁に使えわれるレゴリスの密度によってこの数字は変動する。被曝量の上限についての基準について宇宙飛行士と一般人に対して大きな開きがある点と合わせて考えると、施設に使われるレゴリスや施設を占有する人間のミッションにおける立場により、放射線遮蔽性能と必要な壁の厚さは大きく異なり、壁に求められる厚さの絶対値が出てくるイメージではないことが想像できる。
１．
５メートルでは不足しているであるとか、５メートルあれば十分というような壁の厚さの数字のみを一人歩きさせる議論には注意が必要である。

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図版：鶴巻 崇