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Lunar Base Development Issues,

Technology Requirements, and Research Needs



Peter Eckart[1]




Abstract

The development, design, and construction of a lunar base will be an
extremely complex technical task. It will be even more challenging to set
up the funding scheme and the international cooperative structures that
will be required to establish humankind's first outpost on another
planetary body. This paper provides a summary of development issues,
technology requirements, and research needs of a lunar base program. Non-
technical aspects covered include the rationale for installing a lunar
base, financing, cost, management, and legal issues, as well as general
development aspects. Technical aspects discussed include the impact of the
lunar environment on base design and development, Earth-Moon
transportation, and site selection. The specific requirements of habitat
design, thermal control, power supply, life support, communications, lunar
surface transportation, extra-vehicular activities, and in-situ resources
utilization are discussed, as well as logistics, cost, and modeling
aspects. Also, it is outlined that a lunar base may very well serve as a
testbed for technologies required for human Mars missions. The contents of
this paper are based on countless lunar base-related studies that have been
conducted in the past four decades and The Lunar Base Handbook that has
been published recently and is also introduced here.

Lunar Base Design Activities and Status

Current lunar base studies all build on what may be called the Apollo
Legacy. The Apollo program provided a wealth of lunar data and operational
experience both for Earth-Moon transfers and on the lunar surface. However,
more than thirty years have passed since the first lunar landing and so
many of the experiences of the Apollo era are essentially lost. Apollo also
constitutes a political and psychological burden. Due to what may be called
the 'been there done that'-effect, the public and space agencies have
largely lost interest in the Moon. Only in Japan is lunar exploration on
the space agency's agenda. Consequently, only very few conferences on lunar
or planetary base development and design have taken place in the past 30
years. Nevertheless, numerous lunar base design studies have been
conducted. The focus of these studies was mainly on areas such as in-situ
resource utilization (ISRU) and lunar base habitat design. A comparative
lack of detailed design studies could be observed in other areas, such as
thermal control, communication, and lunar surface transportation. A general
problem is that the different technologies required for a lunar base have
very different Technology Readiness Levels (TRLs). Studies on lunar base
models have been published by H.H. Koelle, P. Eckart, and others. While
Koelle's model is mainly focusing on large-scale lunar bases, the focus of
Eckart's model is on initial lunar bases with few crew members, providing
first order of magnitude estimates of lunar base initial / resupply masses,
power requirements, and heat loads, etc. [Eckart, 1996a; Koelle, 1999]
There was also a lack of coordination between lunar base-related
activities, including space agency studies and academic efforts, as well as
commercial attempts and individual activities. Two groups that are trying
to provide coordination are the Subcommittee on Lunar Development (now:
Moon-Mars Committee) of the International Academy of Astronautics (IAA) and
the International Lunar Exploration Working Group (ILEWG). ILEWG was
founded in April 1995 and its members are space agencies, research
institutes, industry, and universities. However, neither of these
organizations has been able to overcome the general lack of an
organizational structure of the lunar base community. [IAA, 1999; ILEWG,
1999]

Lunar Base Rationale


The first order of business of any future lunar base development initiative
needs to be the definition of a clear rationale. This rationale can be
essentially composed of a:

Scientific rationale (Science of / from / on the Moon)
Economic rationale (e.g., in-situ resource utilization)
Cultural rationale (e.g., evolution of humankind)

Scientific and economic reasons for lunar base development need to be truly
justified, i.e., they should be the best or only alternative to reach a
specific scientific or economical goal. With respect to 'Science of the
Moon', the lunar community has to work on explaining to the public that the
Moon is still mainly 'terra incognita', that there is still much to
discover and so much we do not know. Long-term prospects of a lunar base
need to be clearly defined without raising false expectations, especially
with respect to the Moon's economical potential.


Preferably, the lunar base should be an element of a step-by-step 'Roadmap
of Human Space Exploration'. For example, the lunar base could be a
stepping stone towards the further exploration of the Solar System. In this
respect it may be interesting to note that John Young, former Gemini,
Apollo and Space Shuttle astronaut and now Associate Director for the NASA
Johnson Space Center (JSC), pointed out at the Lunar Base Development
Conference in July 1999 in Houston, TX, that from his point of view
humankind will have to go back to the Moon first, before human mission to
Mars can take place. Based on his personal experience there was still so
much to learn before the risk of a Mars mission could be taken. Young also
emphasized the Moon's potential role in global change detection, astronomy,
and planetary defense, i.e., keeping a watchful eye on asteroids and comets
that are potentially dangerous to the Earth. In any case, lunar base
development as a goal should be back on the official agendas of the world's
space agencies, at least by the time the International Space Station will
be operational. Commercial missions to Moon may be conducted in parallel.
[Eckart, 1999; Young, 1999]


Economical, Political, Legal, and Management Issues


The main economical issues that are related to the establishment of a lunar
base are (a) how to finance it and (b) to define its economical potential.
Although an increasing number of entrepreneurs are interested in commercial
uses of the Moon, it appears unlikely that these efforts can lead to a
private lunar base development program in a relatively near future. Due to
the cost associated with a lunar base program, it is likely that public
funding and agency involvement will be required. The economical potential
of a lunar base should also be defined in a step-by-step approach. While or
after the first step of a development program is taken (e.g., during or
after a precursor phase), the economical prospects of the next phase can be
defined in a much more credible fashion. Long-term projections may be
useful, but should carefully try to eliminate unknowns in the development
plan.


The availability of funding will strongly depend on the opinions and
attitudes of public and politicians. A lunar base will not be funded unless
a public majority supports this endeavor. Therefore, it will be important
to first define the political dimension of lunar base development. After
the government and the public motivation to support a lunar base have been
evaluated, it will be possible to influence space policy and public opinion
and thus ensure the required support. The main legal issue is certainly the
applicability of the 'Common Heritage of Mankind'-principle that is stated
in the Moon Treaty. Although this aspect may have a severe impact on the
exploitation of lunar resources, legal issues are certainly not on top of
the current agenda, given the state of development. It is also unclear
whether we will have suitable management strategies and planning for a
project as complex as a lunar base. However, it can be assumed that those
tools could be developed in time or as the project progresses. [Eckart,
1999]


Site Selection


The selection of a lunar base site will be strongly influenced by the focus
or rationale of the base and the power supply method. For example, if the
focus of the base were on ISRU, it would have to be ensured that
appropriate resources are available at the site. Also, specific science
goals may call for different locations on the lunar surface. Simplifying
the selection categories, the main issues will be (a) polar vs. non-polar /
equatorial site and (b) far side vs. near side / limb site. Due to the
energy storage requirement for the lunar night that lasts approximately 14
days at non-polar sites, the use of solar power is virtually impossible
there, at least using current energy technology. This problem could be
solved through the application of nuclear power supply systems. Continuous
solar power supply may be provided in some permanently lighted areas that
probably exist on some mountains in the lunar south polar region. Other
technical site selection criteria include surface topography, site
accessibility, lighting requirements, surface temperatures, as well as
communication and tracking requirements. [Eckart, 1999]


Lunar Base Development Issues


At the beginning of a lunar base program, a development logic should be
defined that is agreed to by all parties involved. As described in the
previous section, the central issue will be the focus of the lunar base.
Based on a rationale, a lunar base development program will likely be
comprised of the four 'classical' phases:


Precursor Phase


Pioneering Phase


Consolidation Phase


Settlement Phase


Once such a four-phase program has been set up (of course, with a
decreasing level of detail for later phases), the research needs of the
first phase can be more clearly defined. Considering that we are still in
the precursor phase, our current focus should be on projects that are
principally feasible, given the financial and technological constraints.
Hardware projects should mainly build on commercial-off-the-shelf (COTS)
equipment. Studies should focus on analytically investigating the most
urgent technology trades and logistics issues. [Eckart, 1999]


Lunar Base Elements & Surface Infrastructure


The definition of the required lunar base and surface infrastructure
elements can be derived from the functions to be provided. During this
selection process, numerous trade studies will have to be performed, for
example, investigating the use of rigid modules vs. the use of inflatable
modules. Once all elements are defined, lunar base layout strategies can be
investigated. The definition of the layout needs to consider the relative
location requirements of the different elements. Also, the required site
preparation and construction tasks need to be taken into account. In a next
step, lunar surface assembly strategies can be developed. Due to major
problems that are to be expected because of the lunar dust environment, it
may be useful to develop and apply design guidelines for lunar structures
and equipment, to minimize the effects of lunar dust. [Eckart, 1999; Young,
1999]


Lunar Base Thermal Control
The main thermal control problem on the lunar surface is the rejection of
low-temperature heat around lunar noon, when the background (or sink)
temperature may be higher than that of the low-temperature heat to be
rejected. Relatively few studies have been conducted in this area.
Especially, further studies regarding the use of heat pumps and or radiator
shades need to be conducted. Heat pumps are used to increase the
temperature of the heat to be rejected. The application of radiator shades
leads to a reduction of the effective sink temperature. Another thermal
issue that needs to be addressed is cryogenics storage on the lunar
surface. Cryogenic propellants may be required to refuel lunar transfer
vehicles. [Eckart, 1999]

Lunar Base Power Supply

As indicated above, the lunar night lasts approximately 14 days at non-
polar locations. Consequently, it appears virtually impossible to use
exclusively solar power supply systems there. Current technology could not
provide mass-efficient energy storage systems for night-time power supply.
Even the use of regenerative fuel cells (RFCs) could result in an energy
storage system mass that may easily outweigh the mass of all other lunar
base systems combined. [Eckart, 1996a] This problem could be solved through
the application of nuclear power supply systems. However, it remains to be
seen whether the use of nuclear power in space will be politically feasible
in the future. Also, the required nuclear fission systems would still have
to be developed. Continuous solar power supply may be provided in some
permanently lighted areas ('peaks of eternal light') that probably exist on
some mountains in the lunar south polar region. Although lunar base power
supply is probably THE single most critical aspect of lunar base
development, not too many studies have focused on this issue in the past.
[Eckart, 1999]

Lunar Base Life Support

Providing a life support capability at a lunar base should not be a major
problem, as far as physico-chemical life support systems are concerned. Far
more complex is the inclusion of bioregenerative life support technology.
The ultimate goal of advanced life support is to minimize the resupply of
consumables. This may also be achieved by growing plants for food supply.
Despite the extensive research in this area, mainly funded by NASA at JSC
(BioPlex Project) and other locations, it will probably take several
decades until fully-integrated bioregenerative life support systems for
application in space will be available. Even then, these will actually be
hybrid systems because numerous physico-chemical elements will still have
to be included. Although the author of this paper argues that the use of
plants in life support systems will probably not yield any overall mass
savings [Eckart, 1996a], it needs to be stressed that plants should
certainly be included in future life support systems for psychological and
nutritional reasons. Human missions to Mars will also benefit from this
research because reduction of transportation mass and self-sufficiency are
even more critical for this type of mission. [Eckart, 1996b; Eckart, 1999]

Communication and Navigation Systems for a Lunar Base

Relatively few studies have been conducted in past years regarding the
definition of a communication and navigation systems architecture for a
lunar base. The main issue regarding a lunar base communications
infrastructure is whether it should rather be a ground-based or a Deep
Space Network (DSN)-type architecture, i.e., space-based. In either case
the need for additional ground-based or space-based systems will have to be
investigated. Depending on the location of the lunar base, additional relay
satellites may be required in lunar orbit or at the Lagrangian point behind
the Moon (L2). Navigation requirements for lunar transfer and on the lunar
surface will decide the need for a kind of global positioning system (GPS)
in lunar orbit. If the requirements are not too stringent, tracking from
Earth in combination with a lunar surface based system may be sufficient.
[Eckart, 1999]

Lunar Extra-vehicular Activities (EVAs) & Surface Transportation Systems


The definition and development of space suits, portable life support
systems (PLSS), and surface transportation systems can draw extensively
from experiences gained during the Apollo missions. The major difference is
that EVA equipment and surface vehicles for a lunar base will have to be
reused frequently. Maintenance requirements, that will be mainly due to the
impact of lunar dust, will have to be minimized. The major design trade
involved concerns the selection of lunar base habitat pressure and space
suit pressure. For example, operational aspects drive for a relatively low
suit pressure, while safety issues drive for a relatively high habitat
pressure. The larger the pressure differential, the longer will be the
prebreathing requirements before an EVA can take place. Ideally, the
duration of prebreathing should be reduced to zero. Technology development
requirements for space suit and PLSS will also be driven by the need to
minimize the mass of the equipment. The number of pressurized and
unpressurized surface vehicles needed at a lunar base will strongly depend
on the focus of the base, and thus the functions to be provided. [Eckart,
1999]


In-situ Resource Utilization (ISRU) at a Lunar Base

Numerous studies on the use of in-situ resources on the lunar surface have
been conducted in past decades, and a large number of reports and papers
have been published. Research on various ISRU concepts is ongoing,
especially regarding the extraction of oxygen from lunar soil. The main
task of the upcoming years will be to define short lists of the most
promising processes for the extraction of the most important resources,
including not only oxygen, but also hydrogen, aluminum, and others. Then,
the aim should be to increase the Technology Readiness Levels (TRLs) of the
most promising concepts. Currently, most concepts have only reached a TRL
of 2 or 3 (conceptual design formulated and possibly tested). Long-term
logistics studies should investigate whether lunar ISRU may support Mars
missions in an economical fashion. [Eckart, 1999; Lewis, 1993]

Lunar Base Logistics and Cost


Apart from the development of technology, the investigation of lunar base
transportation and logistics issues will also be extremely important. For
example, suitable launch systems, the most important prerequisite for lunar
base development, are not available at the moment. Currently, the
investigation of single-stage-to-orbit (SSTO) launch systems with
relatively low payload masses into Earth orbit is in fashion. However, a
serious lunar base development program will definitely require heavy-lift
launch capability, most likely 'big dumb boosters', possibly two-stage-to-
orbit (TSTO) or SSTO. Another important issue will be the definition of
suitable logistics nodes and Earth-Moon transportation scenarios. In this
respect the scheduling of missions may become rather sophisticated. For
example, the return of a transfer vehicle from the lunar surface to a space
station in low Earth orbit (LEO) is subject to severe timing constraints.
On the other hand, logistics scenarios including the export of lunar
resources, e.g., in support of Mars missions, may even provide a rationale
for lunar base development. Credible cost estimates will be required for
every stage of lunar development. The lack of an appropriate experience
base makes cost estimations for a lunar base program extremely difficult.
The only solution to this problem can be the continuous improvement and
refinement of existing cost models. [Eckart, 1999]


The Lunar Base Handbook


The issues that could only be very briefly addressed in the previous
sections are extensively dealt with in The Lunar Base Handbook that has
recently been published by the author of this paper. The book is an
introduction on lunar base design, development, and operations and provides
an overview about:


The Moon and its environment


The current status of lunar base design


Tools we need to design a lunar base


Checklists and flowcharts that outline the design process


Technological requirements of a lunar base


It includes 24 chapters on about 880 pages covering engineering and
technology aspects, as well as development, legal, economical,
transportation, and cost aspects. The book provides historical background
and an outlook into the future, beyond a lunar base. More than 50 leading
space experts have supported the book as reviewers and / or by providing an
introductory essay for one of the chapters. This group includes Apollo
astronauts Buzz Aldrin, Harrison H. Schmitt, and John Young, as well as
Arthur C. Clarke, Jeffrey Hoffman, John Logsdon, David McKay, Wendell W.
Mendell, Carl Pilcher, and many others. [Eckart, 1999]


Conclusions


This paper has outlined a number of steps that need to be taken in order to
define and implement a lunar base development plan. Specifically, it is
suggested that the community justifies the lunar base case by defining:


A lunar base within the frame of a roadmap of human space exploration


A lunar base development plan based on a stepwise approach


Lunar base functions and requirements


Technology and science research issues


In order to obtain sufficient public and political support, the lunar base
community also needs to conduct an extensive lobbying campaign. A
convincing rationale and business plan for lunar base development has to be
provided. Care should be taken not to raise false expectations by
prematurely overselling the Moon's prospective benefits - whether as a
power-generating station for beaming energy throughout space or as a site
for mining Helium-3. To achieve all this, an infrastructure should be set
up that integrates most, if not all, of the current lunar base activities,
including the IAA's, ILEWG's, and others. The lunar base community can
probably learn a lot from the Mars Society in this respect. The goal of
this effort should be to be ready when the time has come for the start of a
lunar base development program.




References

Eckart, P. (1996a). Parametric Model of a Lunar Base for Mass and Cost
Estimates. Ph.D. Thesis, 250 pp., Technical University of
Munich, Germany / Herbert Utz Verlag, Munich, Germany.
Eckart, P. (1996b). Spaceflight Life Support & Biospherics. 450 pp., Kluwer
Academic Publishers, Dordrecht, NL / Microcosm Inc., Torrance,
CA.
Eckart, P. (1999). The Lunar Base Handbook. 880 pp., McGraw-Hill
Publishers, New York, NY.
IAA (1999). http://vulcain.fb12.tu-berlin.de/ILR/personen/hh_koelle.html

ILEWG (1999). http://ilewg.jsc.nasa.gov/

Lewis, J. et al (1993). Resources of Near-Earth Space. University of
Arizona Press, Tucson, AZ.
Koelle, H.H. (1999). http://vulcain.fb12.tu-
berlin.de/ILR/personen/hh_koelle.html
Young, J. (1999). Keynote Address. Lunar Base Development Conference,
Houston, TX.

NOTE: This paper is implicitely based on countless references. They are too
numerous to be listed here. Detailed lists of references can be
found in most of the publications and web sites indicated above.
-----------------------
[1] Assistant Professor, Division of Astronautics, Technische UniversitДt
MЭnchen, 85747 Garching, Germany, email p.eckart@lrt.mw.tum.de