Executive Summary: NASW-4460
By Cheryl Lynn Singer
The Lunar Base Research Team of the Oregon L5 Society, Inc. proposes development of a lunar analog facility at a lava tube complex in Central Oregon. The city of Bend has donated a lease on the site. Under this contract, sponsored by the Innovation Outreach Program of NASA's Office of Exploration, a surface survey and site maps have been produced, a preliminary engineering study has addressed the structural characteristics of the caves, and the geology of the site has been described and compared to what is known or theorized concerning extraterrestrial sites. The local environment, history of the site, and archeological and educational issues are discussed. Responses to a "Survey of Potential Users" are considered, and a physical plant outlined. A Phase One Development Plan and cost schedule for the proposed Oregon Moonbase Facility is recommended.
Rights were purchased to use existing maps of the Oregon Moonbase lava tubes. Survey of the site, a surface map, five cave entrance maps, and a surface/subsurface composite map were subcontracted. Preliminary subsurface centerline data was collected. Specialized maps can be found with specific report sections. Detailed subsurface mapping of the lava tubes is recommended.
Oregon Moonbase Environment
The Oregon Moonbase site is located within three kilometers of the Bend, Oregon airport and has good access by road. It lies upon basalt plateau covered by sand, volcanic ash, grass and brush, and juniper trees. There are more than 1400 meters of known lava tube caves on this site. Bend has a dry Great Basin climate with average extremes ranging between 35°C (95°F) and -20°C (-4°F), with average humidity less than 50%. Within the caves, the temperature and humidity are more stable. Recorded temperatures range from 2.2°C (36°F) to 13°C (56°F), and humidity is quite high, around 80.6% ± 5%. Except for the entrance areas, the lava tubes show little sign of life other than heavy woodrat use. Particulates from the volcanic ash, rat leavings, and other factors cause the Lunar Base Research Team to recommend air and soil testing. Environmental monitors would be emplaced. An Environmental Assessment at a maximum estimated cost of $100,000 will be required before development commences.
Oregon Moonbase Site History
The Oregon Moonbase site is described, including its three lava tube caves (widest span 24 meters, highest ceiling 8 meters, figures approximate). These caves were used prior to the eruption that formed Crater Lake in 4800 BC. The site does not appear to have been reoccupied until between 0-1500 AD. A major wagon road passed near the site in the late 1800’s. During Prohibition neighboring caves housed illegal stills, though no remains of one are known at this site. Recreational use was heavy in the 1960’s and 1970’s causing a great deal of disturbance to the caves. The site has seen decreasing use since patent to the City of Bend in the early 1980’s. In 1989 the Lunar Base Research Team ran an educational lunar base mission simulation in the lava tubes with fifteen children and parents and five instructors. A tour of the site was given to eight professional cave managers later that year. In addition, the Team conducted routine maintenance activities and baseline observations in 1989. Analysis of litter and footprints indicates the caves were visited by a total of no more than twenty uninvited guests in four or five episodes, almost exclusively during summer months. Only one such event resulted in significant damage to gates and cave features. Preliminary security recommendations are presented.
Geology and Comparative Planetology
The lava tube cave system at the Oregon Moonbase site is developed in highly vesicular, olivine-bearing diktytaxitic basalt, in which laths of plagioclase are jumbled together like jackstraws, with no preferred orientation. The system associated with these caves consists of complex, anastomosing channels. The tubes are partly-filled with remnants of the final lava flow, which did not drain completely. Field studies indicate this system had a protracted history of multiple lava flows, roof breakdown, and later re-roofing and re-veneering. Sediment infill is concentrated near the entrances and is mostly reworked Mazama tephra emplaced by rare large local floods. Sediment grains are subangular but encrusted with very fine authigenic crystals from chemical weathering (see scanning electron micrographs). The lava vesicularity indicates the presence of volatiles in the melt, which suggests that lava tubes may be rarer on airless bodies such as the Moon and Mercury. Mars has locally-abundant volatiles and there lava tubes may be somewhat more common. However, an even more important consideration may be the need for the lava tube to drain after its formation, which depends partly upon local relief, average slope, and the flow volume. Therefore, to find lava tubes on other bodies it will probably be most efficient to first seek out topographic situations where their formation will be favored before carrying out detailed exploration. Most of the possible lunar lava tube features noted by Greeley appear to be around local topographic highs. As suggested by many workers, rilles may be guides to lunar lava tubes.
of the Oregon Moonbase
Terrestrial lava tube sediments may be dustier than lunar regolith, because extremely fine authigenic minerals form by chemical weathering. The impression of overwhelming dustiness of the lunar surface may largely reflect a difference in perspective: aerospace engineering does not usually have to contend with a dusty environment, but terrestrial construction and mining deal routinely with great amounts of dust. Of course, many routine dust palliatives such as wetting with water or oil will not be applicable to the Moon. Dust-sized material is commoner on the Earth than on the Moon. On Mars, chemical weathering is likely to be important, based on observed abundance of fine dust and on reactions driven by solar ultraviolet energy.
Terrestrial lava tubes are geologically short-lived features, worn away by erosional and tectonic processes. Since volcanism on the Moon stopped by 2.5 billion years ago, and since there has been little tectonic or weathering effects, lava tubes could last far longer there. Once a lava tube is formed on the Moon, all that is capable of collapsing it is a direct hit by an impacting body.
Further work to refine data about the Oregon Moonbase cave system is suggested.
Preliminary Engineering Analysis
In general, the lava tubes at the Oregon Moonbase site should be suitable for the project. With proper design and construction techniques, the cave should provide reasonable simulation of a lunar base. Roof thickness measured during core drilling ranged from 3 to 6 meters (10 to 20 feet), but is thinner in some areas. Strength of the roof is highly variable because of thickness, fracturing and cave widths. Calculated allowable loads for either overhead (on outside surface) or suspended loads (including safety factor) range from 6,680 to 178,145 kg/m (4,500 to 120,000 lbs per lineal foot) along the cave centerline. Anchoring for cave roof support and for attaching equipment to cave walls and roof will likely consist of rock bolts. Techniques for creating openings in the lava tube and for clearing the lava tube of debris are discussed. Development and construction in the cave will likely cause some presently weak roof areas to collapse, although techniques are discussed for strengthening the cave roof. Safety regulations implemented during construction should be those specified by OSHA for tunnel construction.
of the Oregon Moonbase
Sand fill in the cave varies from 0 to 1.8 meters (6.0 feet). Average depth of sand is 1.1 meter (3.5 feet); average width of the West Passage is 11.4 meters (37.5 feet) and its length approximately 335 meters (1,100 feet). Approximately 4,180 cubic meters (5,500 cubic yards) of sand is estimated to cover the West Passage floor.
Prior to design of the Oregon Moonbase, further exploration is warranted. Additional borings, full scale load tests on rock bolts, and a seismograph survey are recommended.
Phase One Development Plan:
The proposed location of the Oregon Moonbase is designated as an archeologically significant site. This situation is considered to be almost unavoidable at any lava tube site with surface access. A preliminary study done in 1982 by an ad hoc consortium is included as Appendix A of this report. This study provides more archeological information than is available for most lava tube sites, thus it is possible to broadly estimate the cost of the necessary archeological recovery at a total of $638,000. Direct NASA funding of the excavation is recommended to allow Oregon Moonbase development to go forward with the speed required to meet anticipated demand.
Oregon Moonbase Archeological Issues
Survey of Potential Users
Copies of the Oregon Moonbase "Survey of Potential Users " were distributed to aerospace industry researchers and managers, NASA officials, and a diverse lot of other parties potentially interested in planetary base analogs. Most critical requirements were for verisimilitude and availability of support systems, but cost was also a significant factor. Some estimated facility use data was collected. Many respondents are highly enthusiastic, and some reported having systems to test now or in the near future.
Education at the Oregon Moonbase
The Oregon Moonbase project grew out of an educational lunar base mission simulation activity for local chapters of the Young Astronauts Program. Lunar Base Research Team members recognized the potential of a permanent lunar base analog facility in Central Oregon for both education and research. A workshop with educational professionals was held. Educators echoed the advise of researchers that the Moonbase project should make research its first priority. Methods of integrating public outreach, education, and training into the project were described. The Oregon Moonbase could become a significant training facility for lunar and Martian base crews.
Phase One Physical Plant
The physical plant of the Oregon Moonbase will utilize all the advantages of a lava tube site in supporting experimental and training systems. Its 400 kilowatts of electrical power provides for load demands expressed in our User Survey. The water storage and distribution systems will meet the needs of the humans, flora, and fauna of an integrated lunar base analog. The security for these systems will include both passive and active systems. The Facility Operations Center will provide communications for each of the eight experimental sites, as well as office space for Oregon Moonbase staff, and eating facilities and showers for staff and clients. A Teleoperations Center will allow testing of teleoperated robots at each experimental site without the cost of high-bandwidth communications links to other locations around the country. These support systems will allow cost-effective and prompt testing of a wide range of lunar and Martian base technologies.
Phase One Development Recommendations
In order to meet anticipated demand for cost-effective analog testing that can minimize risk and increase confidence, the Lunar Base Research Team recommends that NASA fund the development of the Oregon Moonbase according to the schedule which follows. Specific aspects of the plan are discussed. Additional related studies not included in the scope of the current project are also recommended.
Phase One of the Oregon Moonbase is anticipated to be completed in four years. By the middle of Year Two, the facility will provide experimental support systems to users. Year Four will see the completion of these systems and a plan for Phase Two development: two simulated Lunar Outposts (one surface, one subsurface). Preliminary cost estimate for Phase One is $6.2 million. A schedule of activities and estimated expenses is outlined.
Preliminary archeological assessment of areas in the Oregon Moonbase site (1982).
Lava tube Habitats as a cost-effective base siting option are discussed.
History of the Lunar Base Research Team and the Oregon Moonbase project is presented.