Evolving Lunar Lava Tube
Base Simulations with Integral
Photos ©1988 Bryce Walden
Thomas L. Billings*, Pacific Rim Space Education Center (PaRSEC)
Oregon Museum of Science and Industry (OMSI)
4015 SW Canyon Rd., Portland, OR 97221
Bryce Walden, B.S. Purdue, President
Oregon L-5 Society, Inc., Chapter of National Space Society
P.O. Box 86, Oregon City, OR 97045
Jan Dabrowski, Ph.D., Director of Science Programs, OMSI
4015 SW Canyon Rd., Portland, OR 97221
(Presented to the Second Symposium on Lunar Bases and Space Activities of the 21st Century, Houston TX, April 5-7 1988)
Facilities are being created in central Oregon to simulate lunar bases in lava tube environments. Horz (1985) details the economic and operational advantages of locating bases in lunar lava tubes. The present program uses terrestrial lava tubes to build stepwise into realistic simulations of lunar bases and support systems. Site and feasibility studies were conducted in summer, 1987. In the following months Young Astronauts and SEDS workers set up modular workstations and performed predefined tasks in and around a lava tube base. Results of these simple simulations suggest that the advantages of lava tube bases outweigh the problems. Several areas of technology can be investigated, including structures, recycling, and energy systems. An integral instructional capability allows mission simulations earlier in the project. Full lunar lava tube base simulations will be phased in as the instructional facilities grow in sophistication and scale.
The concept of lunar bases inside lunar lava tubes was suggested by F. Horz in his 1985 paper, "Lava Tubes: Potential Shelters for Habitats." Lava tubes are made by crusting over of lava channels (Greeley, 1971; Harter & Harter III, 1982; Greeley & Spudis, 1986). Lunar lava channels, or sinuous rilles, some of which appear to have uncollapsed roof segments, have measured widths of from 200m to 1.5km. Roof thickness in excess of 10m provides meteorite and radiation shielding and moderation of surface temperatures (Horz, 1985). An entrance is easily cleared into the shielded environment of a tube for the largest machinery.
Simulations on Earth are part of the immense engineering effort required to solve many of the problems of a lunar base. Simulations can also be used for instructional purposes adjunct to a wide range of educational programs. Educational simulations build experience and support structures so the least new investment is required for testing any new system. This low-cost testbed promotes the widest possible range of responses to the demands of lunar engineering and the possible social structures of lunar bases.
Mission Simulations 1987-88
National Speleological Society authors Charlie and Jo Larson advised the project team about caving and locations of regional lava tubes. Exploratory cave surveys started in April 1987 and continued through that summer. The clear favorite was Skeleton Cave, on U.S. Forest Service land about 29 km from Bend. Its 10m width, 6m height and 925m length (Larson & Larson, 1987) is about 1/15 the size of projected lunar lava tube caverns (Horz, 1985).
In August 1987 the project team conducted a feasibility study for future simulation exercises at Skeleton Cave. The team used construction systems and sanitary facilities like those for subsequent exercises. Conclusions were that a simulation involving Young Astronauts and SEDS (Students for the Exploration and Development of Space) was feasible and safe.
The first full-scale lunar lava tube base simulation was conducted at Skeleton Cave on October 23-25, 1987. Every level of activity was tested: organization, logistics, construction, and education. The simulation included a surface camp with the lunar base 470m inside the cave. The lunar base consisted of four working modules: a sleep/work platform, a communications desk, a galley, and a sanitation facility. Mission science activities also included cave mapping, astronomy, geochemistry, and environmental monitoring.
The second mission simulation on November 20-22, 1987, added the use of Sunriver Preparatory School as a staging area and introduced the use of inflatable structural beams (Mark I Air Beams) at the base. These structures failed in use and therefore required design changes. New designs were prototyped and tested in the OMSI labs and taken on the third mission.
Further survey missions found a good site on land owned by the City of Bend: Young's Cave complex (Larson, 1982). The third mission ran at Young's Cave with permission from city officials.
Three modules were included in the third mission simulation, on February 26-28, 1988: an improved communications and power module, a sanitary enclosure, and a trial run of inflatable structural beams (Mark II Air Beams). The new beam design worked, as did the new 12v power distribution system. At Young's Cave the educational simulation facility is located 20m inside the entrance, making site logistics much easier than at Skeleton Cave.
Results Of Early Missions
Advantages of terrestrial lava tubes for lunar base simulations are similar to advantages of lunar lava tubes for lunar bases: sizes large enough for major structures; hard basalt walls and ceiling; large 'cubic' sheltered from outside weather; moderate temperatures; and floors that vary from relatively smooth surfaces to huge mounds of rough rock (Harter & Harter III, 1982; Horz, 1985). In addition, fine volcanic dust in this area's caves is an analog to the fine lunar dust that plagued astronauts (Khalili, 1985). This silicic 'dust' from geologically recent local volcanism (Chitwood, 1982) coats every grain of cave sand (revealed by microscopic examination) and forces us to address this expected lunar problem from the very beginning. Dust coats surfaces and contaminates lubricants, interfering with fit and/or operation of some components. Dust suspended in the air can be a respiratory irritant.
Initial simulations revealed these problems: lack of reliable and adequate transport to the site; need for transport inside the lava tube; designs that used materials inefficiently or ineffectively; dust contamination; washbasin design failure; inefficiency of battery-powered incandescent lights; failure of the Mark I Air Beam; lack of stimulation in the deep cave environment; not accomplishing assigned tasks; and participants arriving late or leaving early.
Successes include: low overhead costs of facility; use of a modular construction system; portable sanitation equipment; 12v power supply and distribution system; partial control of dust by tarpaulin floor covering; fluorescent battery-powered lights; intercom communications from lava tube base to surface camp; galley; sleeping/work platform; and the Mark II Air Beam. The above allowed the base to support educational scientific exercises. Successes also include the general structure and organization of the simulation and the proved ability to conduct such simulations.
At present so-called 'easy' caves are used (wide flat floors, few rockpiles) to minimize operational problems and for the safety of Young Astronauts. The caves' large sizes give a sense of spaciousness and help participants imagine lunar tubes with diameters up to 20 times larger. The near-constant cave environment protects equipment and allows workers to wear light-weight clothing, similar to the minimal space suit needed within lunar lava tubes (Horz, 1985)--which is another sub-system that could be tested.
These exercises lead to several conclusions: successful educational simulations of lunar lava tube bases can be run in lava tubes of central Oregon; a lunar base simulation can be performed with personnel of minor age; a permanent site would allow better simulations through use of an evolving base infrastructure on site; a full-time staff would improve organization, scheduling of activities, and data analysis; and using a lava tube saves money, time, labor, and material.
Evolution Of Lunar Lava Tube Base Simulations
The growth and evolution of the lunar base simulation facility has been mapped out for a fifteen-year period. This gives the lunar development community a level and style of simulation appropriate to its growing needs.
Through Year 1
Year 1 ran from April 1987 to April 1988. The project was planned, sites were surveyed, and educational mission simulations were conducted. Physical systems were basic but functional, and capable of being disassembled for transport. Pressure supported structures were designed and used on missions. A 12v base power system was developed. In March 1988 Young's Cave complex was secured as a long-term site from the City of Bend.
Through Year 2
Between April 1988 and April 1989 the project team plans to physically secure the facility site, construct a minimal permanent physical plant, and secure reliable communications and ground transport. By April 1989 personnel will include at least a facility manager and a space education specialist. Graduate groups from major universities can be working on design and construction of base subsystems. Private industry may also conduct research. Education-al simulations will continue and expand.
Papers are being prepared for education, engineering, and science journals. The team's work will be presented to the Lunar Bases Conference of the Lunar and Planetary Institute. Grants will be sought from educational, governmental, and industrial sources.
Through Year 5
The project enters year 5 with its major physical plant in place and continuing modifications involving new designs and technologies. Logistical services can support 50 people and their separate projects for longer mission simulations. A continuing flow of students and researchers will come from participating schools and corporations. Communications will include voice, video, and data links with participating institutions. Telerobotic activity may be directed from participating institutions to the base and/or from operators inside the base to the surface.
To accommodate the increasing use and growing sophistication of the facility funding will be sought for general purposes and for specific activities. Schools and corporations will sponsor projects, modules, and support systems.
Educational and technical advisory groups will coordinate activities and correlate results from participating institutions and corporations. Each project's supervisor will work with the appropriate advisory group and facility management.
Through Year 10
Starting about year 5 industries with lunar sub-system concepts will find a ready testbed for their equipment. The facility may expand to include a large, rough lava tube selected to most closely model expected lunar caverns. Operational training and educational activities can continue at the initial site while the rough site hosts more advanced structures and designs. Communications between sites can model communications between two lunar bases. Groups with competing lunar base designs may bring them to these sites for testing in standard environments.
The activities of the simulation facilities will provide a graphic physical focus for publicizing actual lunar base projects. This will bear fruit for lunar projects by bringing more public attention to them even before tests of lunar-rated designs begin.
Valuable comparisons can be made with lunar surface base simulations (and eventually actual lunar bases). Economic advantages can be evaluated for each type of base. Physical technologies, support logistics, and human factors can be compared and contrasted between sites.
Through Year 15
By year 15 permanent lunar bases may be emplaced in lunar lava tubes. The mature lunar lava tube base simulation facility could become the terrestrial mirror of actual lunar bases, used to troubleshoot problems and train personnel. A duplicate of a lunar base permits compatibility and integration testing of newly designed components before shipping them to the Moon. The facility's extensive historical database may contain clues to the problems that will show up. The facility's small, specialized team with long experience working together can provide good solutions to base problems at a reasonable cost. Part of this team will work at operating lunar bases with their counterparts at the simulation facility doing "quick and dirty" work to get fast solutions.
Looking ahead, the simulation facility could be useful to model Martian bases which may find a home in the lava tubes of Mons Olympus (Greeley, 1987). These caverns may be larger than terrestrial lava tubes due to the size of the Martian volcanos and the gravity of Mars.
Get In Below The Ground Floor!
Success in simulating lunar lava tube bases indicates that this option for lunar base design should be actively pursued and lunar surveys should seek likely sites. Welcome to Moonbase by Ben Bova (1987), gives a construction time of three years to prepare a shield for a surface base. To create a shielded vault 600m long by 75m high requires unshielded "construction engineers and swarms of teleoperated machines" working with "microwave beams and plasma torches," supplied from Earth, for three years. Simply opening an entrance to a lunar lava tube cavern creates as much shielded 'cubic' faster, cheaper, and better!
The interior of the Moon's lava tubes is still 'luna incognita'. There might be rough piles of huge boulders as found in some terrestrial tubes or flat floors as found in others (Harter & Harter III, 1982) [web bonus: Fig. 6 not included in original paper]. The design options to meet these conditions range from light-weight structures hung from the arched ceiling (Horz, 1985) to fused rock huts on the floor (Khalili, 1985; Rowley & Neudecker, 1985). Pressurized 'cubic' and hard vacuum for industry will exist side-by-side under the cavern's shield.
By starting the lunar base simulation as an educational activity, no pretense is made that all the problems of a lunar base are addressed. However, using conventional materials and bare-bones designs, it is possible to model, in simplified form, the planning, logistics, construction, and operation of an actual lunar base. This simplicity is appropriate for first steps and for the ages of current participants. The facility will grow to become a valuable addition to the lunar development community. These activities are among the first steps on the return to the Moon.
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