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Things are heating up on the moon, at least figuratively. August saw the successful touchdown of India’s Chandrayaan-3 lunar mission’s lander and its ride-along rover near the moon’s south pole, as well as the announcement by the U.S. Defense Advanced Research Projects Agency of its seven-month study toward developing a lunar economy in the next decade. All that new focus on Earth’s one natural satellite can only help bolster the space habitat research that was already underway at Lockheed Martin.
As several countries gear up toward sending people to the moon once again and eventually beyond, the need for human space habitats is obvious. When most people envision such a thing, their minds understandably default to the metallic pressurized shells of the 1960s manned lunar landers and the space stations of the past and present, including Skylab and the International Space Station.
Lockheed Martin, the aerospace and security company headquartered in Bethesda, Maryland, and employing 114,000 people worldwide, has a concept that’s completely different. It’s an inflatable shelter made of a flexible polymer yarn, Vectran, a material comparable to Kevlar that is ten times stronger than aluminum and is currently used in ropes for climbers and in racing bike tires. “Why inflatable? At first it sounds crazy,” said Kirk Shireman, VP of lunar exploration at Lockheed Martin. “But it turns out to be a great idea. It turns out to be a very resilient structure.”
There are several significant benefits to the concept. Since everything our astronauts need must be hauled to their destination, an inflatable habitat offers greater ease of transport and the potential for larger living spaces, since its inflated dimensions aren’t as constrained by the size of the launch vehicle fairing as the sizes of rigid habitats are. With no structural frame, the inflatable shelter offers weight savings as well. “Even today in the space industry, mass is king,” explained Shireman. “Volume is next.”
“One of the key advantages of inflatables is that you get more usable volume per rocket launch than with the rigid metal structures currently in use,” said Dr. Paul van Susante, assistant professor, mechanical engineering—engineering mechanics and PI of the Planetary Surface Technology Development Lab at Michigan Tech University. “That in turn reduces the number of launches needed.”
The habitat’s polymer construction can also better shield astronauts from radiation. “When galactic cosmic radiation goes into metal, it hits the nuclei of the metallic atoms and creates secondary radiation,” Shireman said. “I believe we’ll see a much-reduced radiation environment.” The Vectran material is expected to offer improved resistance to leaks and micro-meteor impacts as well.
Lockheed Martin’s concept is aimed at a variety of applications. “To live, you need communications, a place to stay, wheels, and power,” said Rob Chambers, the company’s deputy director of commercial civil space strategy. “We’ve always been thinking, ‘How do we get to Mars?’ Then we say, ‘What are the systems we need for that? What size habitat? How do you move from one place to another? Power? Access to water?’ You need large volumes. Soft habitats are ideal for that. We look at the solution requirements, then work backwards.”
The concept isn’t entirely new. “In the 1990s, NASA developed TransHab, an ISS concept module, and tested it on the ground and developed many of the required technologies,” van Susante explained. “Bigelow purchased the rights and developed a prototype which is attached to the ISS currently. This was a test article for proving the technology in preparation for much larger volume inflatable habitat modules.” The Bigelow Expanded Activity Module, in operation now, provides the ISS with 565 cubic feet of workspace. The development of TransHab and the BEAM spurred NASA to establish specific certification test for inflatables, including burst testing and material creep tests.
Lockheed Martin is well along in its initial tests. “The thing most people struggle with is the burst test,” said Shireman. “We pretty much nailed that on our first try.” Next will be full-scale model burst tests and creep testing for both subscale and full-scale constructions, as well as tackling other structural challenges like adding windows and other protrusions.
“Some items that need additional attention in the design for lunar use compared to use of inflatables in orbit is the interaction with lunar dust–very fine, but very abrasive material–and the orientation of the connections, foundation, and load path to ground to make sure the integrity of the inflatable does not get compromised due to abrasion and wear points,” added van Susante.
“I think it’s the next wave, the next generation of technology for habitation in space,” Shireman said. “It allows us to create habitats more rapidly and at a lower price point. Humans can’t live in space suits full time–we need a place to live and a place to conduct science. This will allow us to carry humans farther from our planet than ever before.”
“The moon is just about ready for business,” added Chambers. “Space exploration is bigger than any one country and far bigger than one company. It’s important for us to have international partners, to appreciate what each country can bring to the table and to develop the moon in a peaceful fashion. The path to Mars has always been through the moon.”