With more than a half-dozen posters available for delegates to view, Gordon Zhou – a young researcher at the University of British Columbia’s department of civil engineering – said in-situ resource utilization (ISRU) is the one theme that unites the posters he wrote with Austin Mardon, at the Antarctic Institute of Canada.
Zhou’s work at the Lunar Exploration Research Group meeting covers summaries of everything from lunar concrete to analogue sites such as that at Devon Island in Canada’s Arctic.
“With limited government funding and private investments, ISRU is an essential part of fulfilling future lunar and space exploration visions by ultimately enabling lower mission mass and cost,” Mr. Zhou wrote in an e-mail interview with SpaceRef. “With the current economical situation, ISRU takes advantage of commonality in resources and processes already available on the lunar surface. From lunar lava tubes to sulphur-based concrete, ISRU is the umbrella that comprise of refining construction material and developing consumables and manufacturable components for infrastructures to support future lunar missions.”
In the United States the lunar exploration program in NASA’s 2010 budget received over $150 million of an approximately $18 billion dollar budget. In Canada, Zhou pointed out, lunar exploration receives only a small fraction of that annually from the Canadian government. However the Canadian Space Agency did receive $110 million in stimulus funding in 2009 to be spent over three years of which a portion is being used to do preliminary design requests for two lunar rovers.
“Comparatively, Canada’s funding for our space program can be seen as modest at best,” Zhou said. “Dr. Mardon is a member of a grant proposal that is being considered by NASA for a lunar analogue in British Columbia. They did not previously get funding in Canada, so had to go outside for funding. In order for Canada to take a leadership role in the future in space exploration projects, more funding must be put in place by the federal government.”
Zhou’s and Mardon’s poster on ISRU pointed out that reducing the amount of material space missions bring from earth is a “difficult obstacle”. The researchers stated areas of focus need to be items such as consumables, repair, manufacturing and surface construction.
In terms of construction, the lunar environment – though bereft of rain, wind and other weather elements on Earth – would still be a challenging environment to build for.
Another poster by the researchers detailed steps to simplify structures for lunar construction. Elements to consider include a vacuum environment and the risk of fatigue as components move between unfiltered sunlight and shadow.
Inflatables are currently the best-known way of addressing that, but the technology (and money) doesn’t exist to manufacture the structures on site. They would have to come with the astronauts. Even once the site is set up, Zhou pointed out there would have to be significant investment from the private sector to set up even a small mining presence to export materials back to earth.
“Based on our geological knowledge of the moon at present, the discussion within the scientific community has somewhat come to an understanding that mining and transporting any lunar mineral back to earth would not be economical,” he said. “The only known resource that is of current interest is helium-3. This is found on the moon and not on earth because the moon has no atmosphere, and charged particles from the sun can impact it and not be deflected. This element is of particular interest for its possible fuel potential in fusion power plants.”
That said, investigation is taking place into at least two types of materials that could be mined and used for structures on the lunar surface, as posters by Zhou and Mardon outline: concrete from regolith, and concrete from lava tubes.
In terms of regolith, Apollo 16 regolith samples examined by Construction Technology Laboratories (now CTLGroup) in 1986 revealed calcium, aluminium and silicon. Calcium oxide is about 12 per cent of the regolith’s weight; along with other elements, the closest earth analogue would be Portland cement, which has 65 per cent calcium oxide.
“Our research interest related to sulphur-based concrete with lunar regolith has shown distinct properties and advantages in relations to hydraulic-based concrete,” Zhou said, pointing out the feasibility is also being examined at the NASA Goddard Space Flight Center. “Future work to evaluate other properties such as stress-strain relationship, durability under the lunar vacuum environment and different types of reinforcements and additives must be evaluated.”
Lunar lava tubes are the other possibility for construction. The structures are about 10 times the size of comparable tubes on earth, and are also much older – you can find them in Hawaii as well as Medicine Lake in California, Zhou said.
Since they would use sulphur and not water to form the concrete, Zhou said, lava tube construction would gain strength quicker and retain its strength better without the need of H2O – an expensive and precious commodity that would be difficult to mine from the moon.
However, he pointed out more research is needed on the lunar surface itself before knowing which method would be best – and how best to approach mining materials from it.
“The horizon for this is not the current moment but resources are running out on Earth and companies and governments are looking at this,” Zhou and Mardon wrote in their space mineral resource utilizaton poser. “What needs to be done is a cost analysis of rare minerals that could be accessed eventually.”
— Space Mineral Resource Utilization (Paper 3034 PDF)
— Lunar Exploration Factors for Consideration (Poster 3010 PDF)
— Structural Mechanics in Lunar Design and Construction (Poster 3002 PDF)
— Lunar Concrete Preliminary Feasibility Analysis (Poster 3004 PDF)
— Structural Stability and Sulfur Based Luncar Concrete Components for Lava Tube Suitability (Poster 3001 PDF)
— Lunar Oxygen production Through Hydrogen Reduction at High Temperatures (Poster 3012 PDF)
— Gold Plating for Lunar Solar Protection and Temperature Control (Poster 3019 PDF)