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A sliver of the setting moon photographed by an Expedition 7 crew member onboard the International Space Station, with the

Photo courtesy of NASA

Fly Me to the Moon
UMaine engineers take sensor research to new heights to facilitate lunar habitation

About the Photo:
A sliver of the setting moon photographed by an Expedition 7 crew member onboard the International Space Station, with the Earth at the bottom transitioning into the orange-colored troposphere.

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In many of the earliest science-fiction imaginings, gleaming structures of glass and steel rise from the surface of the moon and into the surrounding darkness as intrepid colonists zip about them in jet packs and flying cars.

While those nifty space-age modes of transportation have yet to materialize in the real world, the long-envisioned idea of establishing a colony on the moon might actually become a reality in the near future. That's the grand scheme, at least, as outlined in President George W. Bush's "Moon, Mars and Beyond" space-exploration initiative.

The idea is to return to the moon by 2020 and create a self-sustaining research outpost somewhere on its surface. At first, a few astronauts will make several week-long visits until their power systems, rovers and living quarters are functional. NASA then plans to extend the missions to two weeks, then two months and eventually to 180 days.

Within a decade or so, the theory goes, lunar explorers should have enough extraterrestrial experience and skill to make the next giant leap to Mars and perhaps planets beyond.

Of all the many challenges NASA faces in this ambitious endeavor, one of the most critical is providing habitats that will allow humans to live and work safely in the lunar or other harsh space environments. Not only will the structures have to be comfortable enough for long stays, they will have to shield their inhabitants from cosmic rays and radiation while withstanding micrometeorites, moonquakes and surface temperatures that fluctuate day to night from about 224 degrees to minus 243 degrees Fahrenheit. Thus, it will be critical to continuously monitor the dynamic shape of deployable space structures such as lunar habitat and microwave antennas.

Designing such deployable space structures will require engineers to rethink what constitutes a structure, and the methods and materials necessary to build them. That's where University of Maine researchers are hoping to play an important role.

Initial funding by the Maine Space Grant Consortium led to a $1.5 million grant from the NASA Experimental Program to Stimulate Competitive Research (EPSCoR) and UMaine. UMaine electrical and computer engineers Ali Abedi and Mauricio Pereira da Cunha have teamed up with mechanical engineers Vince Caccese and Mohsen Shahinpoor, as well as University of Southern Maine computer engineer Mariusz Jankowski to develop a first-of-its-kind wireless sensor network system to monitor the structural integrity of inflatable space structures after they've been deployed in space.

Easy-to-assemble inflatable structures are considered to be one of the most promising of the habitation concepts now on NASA's drawing board. They're ultra light when compared with building materials used in large earthbound structures, and that's a big plus when launch costs are running about $10,000 a pound and getting one pound of supplies from the Earth to the moon requires 125 pounds of hardware and fuel.

One UMaine graduate student is now working with Caccese to build computer models of how certain flexible materials work, while another is researching a new way to make them rigid once the inflatable structure is deployed.

"NASA is extremely concerned about human safety," Caccese says. "I picture myself being up there, too, and I ask myself what would I like to live in and what would make me feel safe."

It was work by Abedi and Pereira da Cunha on wireless sensing, and Caccese's and Shahinpoor's past experience with smart structures,
that convinced NASA to make the UMaine project one of 13 in a nationwide competition to receive funding.

Abedi says this system would also allow NASA to reduce the miles of bundled sensor wires and connectors that now add so much unwanted weight, expense and potential for failure to every space flight.

As innovative and valuable as that battery-free wireless system may prove to be, Abedi says, the UMaine team's latest efforts in the advancement of space exploration will require technology that goes a step beyond anything that currently exists.

"Today, what we have for sensors, wireless systems and algorithms, none of them can address this new system," says Abedi, who is leading the UMaine team. Once the new sensors are developed, the challenge will be to find a way to embed them into a multi-layer fabric that a leading aerospace contractor in Delaware will use to build a prototype inflatable structure for UMaine researchers.

By sensing the coordinate positions of an array of key points on the inflatable's surface, the wireless system will allow the researchers to visualize the shape of the structure after it is deployed. That final shape data, when compared with computer modeling data, can be used to assess how successfully the structure was inflated and eventually to help in correcting any troubling deformations.

"If there is damage to the deployed space structure from a micrometeorite, for example, we have to be able to determine where that impact occurred, and what kind of damage it caused," Pereira da Cunha says. "That's the first step in this investigation, but once we enable this system, we will be able to expand our research to include other relevant NASA monitoring needs, such as gas, temperature, changes in pressure, etc."

As important as shape constraints are for lunar habitats, they are even more critical to the proper functioning of inflatable antennae. If an antenna is not shaped exactly as its designers intended, its microwave transmission signals are distorted and attenuated, and, ultimately communication may be interrupted.

"The beauty of this project is that wireless technology gives us a powerful mechanism to determine how an inflatable structure has been deployed, and what dimples or wrinkles need to be corrected," says Shahinpoor, chair of the Mechanical Engineering Department, who will use his expertise in smart materials for the rigidization work. "Right now, NASA can't detect or correct these deficiencies."

Although NASA has long been interested in inflatable structures, the educational opportunities such research could provide for students,
as well as its economical development potential, have so far gone largely unexplored at most universities. This project, according to Caccese, could change that quickly for UMaine, USM and the state.

The researchers plan to involve 15 undergraduate and four graduate students in the three-year project. They will be trained in campus
laboratories, as well as at NASA's Johnson Space Center in Houston, Texas, and Glenn Research Center, Cleveland, Ohio, which are collaborating on the UMaine research and development work.

The UMaine team also intends to create new course materials pertaining to the research and to hold seminars for the public at high schools in the state.

"It helps the university and the whole state to get students excited about this," Abedi says. "I think this will put UMaine on NASA's map."

by Tom Weber
November-December, 2008

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