Published: May 29, 2007 1:00:00 AM
Media Contact: ,
If you had a brand new car, you wouldn't leave it parked outside in a bad storm, would you? Likewise, astronauts on the moon would prefer to park the lunar roving vehicle in some kind of shelter or "garage".
That's why scientists and engineers at the Marshall Center and engineering professors at Auburn University in Auburn, Ala., are working on a concept for a lunar shelter that would protect rovers and other equipment from meteoroid strikes, radiation damage and extreme temperature swings.
The shelter would be built of bags made of woven polymer - a reinforced material such as Kevlar TM, used in tires and bulletproof vests - and filled with raw lunar regolith, or moon dirt and rocks. The bags would be stacked somewhat like sandbags to form the shelter.
Auburn University professor Dr. Roy Broughton holds seven samples of polymers he plans to have tested in Marshall's Atomic Oxygen Beam Facility. (NASA)
Dr. Roy Broughton and Dr. David Beale, both of Auburn University; and Gweneth Smithers, an engineer in Marshall's Nonmetals Engineering Branch of the Engineering Directorate, recently analyzed a number of polymer materials such as VectranTM, NextelTM and GoretexTM for their structural properties and strength under extreme temperatures. Mary Hovater and Scott Miller, of Marshall's Environmental Effects Branch of the Engineering Directorate, then tested these materials in simulated space environments.
Strips of the polymer samples were exposed to both ultraviolet and electron radiation in the Marshall Combined Environmental Effects Facility - a lab that uses a solar simulator to test the samples.
Marshall's Micro Light Gas Gun was used in the tests to simulate meteoroid impact on fully loaded bags of regolith. The tool shoots 1-millimeter-diameter particles at speeds around 7 kilometers per second, or 15,600 mph.
A full-scale lunar shelter prototype was built in Marshall's Space Systems & Integration Test Facility. (NASA)
A full-scale prototype arch for a garage and proof-of-concept was built at Marshall. Kevlar TM fabric was woven by Lincoln Textiles of Opp, Ala., and sewn into bags by Kappler Inc. of Guntersville, Ala. The bag were filled with vermiculite - a type of potting soil that holds water very well and is neither acidic nor alkaline - to simulate a variety of soil sizes, just like you would find on the moon.
The prototype was assembled in Building 4493 - the Space Systems Integration & Test Facility. A coating was needed on the Kevlar TM to keep fine dust from seeping out of the bags. "The shelter seemed to stand up to the testing very well," said Carole McLemore, project manager for Marshall's In Situ Fabrication and Repair/In Situ Resource Utilization Office, which funded the regolith bag research. "We are pleased to work with Auburn University on such an exciting endeavor."
Auburn is continuing its coated polymer work for another space endeavor - tethered satellites. Broughton recently delivered seven samples for testing in Marshall's Atomic Oxygen Beam Facility - used to accelerate oxygen atoms towards a material sample with the same energy you would find on orbit.
Most polymers break down quickly in low-Earth orbit because of atomic oxygen erosion. Ultraviolet radiation from the sun breaks down molecular oxygen in the upper atmosphere into oxygen atoms. When a spacecraft is moving 17,500 mph in low-Earth orbit, it hits those oxygen atoms with enough energy to break the bonds of most polymer materials.
Auburn is experimenting with various coatings that can protect the polymer from this erosion without impacting the flexibility and strength needed for a space tether.
The writer is a NASA employee in Marshall's Engineering Directorate.