By Jean Thilmany, Associate Editor

After making footprints in the dust and planting the flag, the first astronauts on Mars—whenever they arrive—will have to set up housekeeping.

Unlike Neil Armstrong and all the Apollo astronauts who followed him to the moon, the humans who land on Mars will be stranded there for months until its alignment with Earth lets them return home. And that means establishing a base and starting up a generator to power it. Since every ounce of equipment is at a premium, the ideal would be to forgo hauling fuel to the surface and instead rely on an on-site power source.

The solution, some NASA scientists say, may be wind turbines like those designed to deliver electricity at the Earth's bitterly cold South Pole and in remote regions of rural Alaska. Mars wind turbines could generate electricity during months-long global dust storms that can make days on the red planet as dark as night.

Future Mars colonists would need to establish a base. Some NASA scientists say that wind turbines could provide electricity for the astronauts.

David Bubenheim, a scientist at NASA's Ames Research Center in Moffett Field, Calif., envisions a Mars space station powered by solar energy during clear weather, with wind-generated power picking up the slack during the dark months. The small wind turbines that Bubenheim and his fellow scientists are considering for such a project are currently used for NASA projects in Antarctica, where the continent's six months of darkness each winter make it impossible to rely on solar power year-round.

"Wind power and solar power may complement each other on Mars," Bubenheim said. "When you have a large dust storm blocking the sunlight, a wind turbine can still generate electricity."

There's a key to that complement. The Mars wind blows strongly enough to move an energy turbine only during dust storms. At other times, the planet is still, said Michael Flynn, also a scientist at the Ames Research Center. Mars turbine research is carried out through NASA's Cold Weather Wind Turbine program.

WIND AS AN ENERGY SOURCE

To understand how wind turbines make electricity, think of a wind turbine as rather like a fan, only backward. Instead of using electricity to make wind as a fan does, the turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator that produces electricity. Utility-scale turbines vary in size; they're capable of generating from 50 kilowatts to more than 2 megawatts. The turbines being looked at for the Mars project generate about 100 kW, depending on the location and the thickness of the air. At an Alaska test site, the turbine clocked a maximum of 120 kW in a 36-mph wind. At a test site in Colorado, where air is denser, it averaged closer to the expected 100 kW, said an Alaskan utility company engineer.

On Earth, wind needs to blow at about 10 meters, or 33 feet, per second to operate a wind turbine, Flynn said. On Mars, it has to blow at about 30 meters, or 98 feet, per second because the planet's atmosphere is extremely thin.

Some homes, telecommunications dishes, and water pumps are powered by small turbines that generate energy at levels below 50 kW, according to the U.S. Department of Energy.

Wind turbines are often grouped together into a single power plant, known as a wind farm, to generate bulk electrical power. Electricity from these turbines is fed into the local utility grid and distributed to customers, just as electricity is distributed by conventional power plants.

Turbines can generate big returns mainly because they can be easily located in remote regions of the globe—and, of course, potentially on Mars—where access to electricity is limited or non-existent, and where even small amounts of electricity can significantly improve the quality of life, the DOE says.

Take rural Alaska, for example. Folks in Kotzebue, Alaska, recently saw installation of a new Northwind 100 wind turbine prototype made by Northern Power Systems of Waitsfield, Vt.. That's the same company NASA is working with to develop hybrid wind-solar systems. Kotzebue is located on the Bering Strait north of the Arctic Circle and is home to the tribal government of the Qikiktagrukmiut people, the original inhabitants of the area. The only way to access the region is by air.

The Kotzebue Electric Association already uses 66-kW turbines for electrical generation. The new Northwind 100 turbine provides about 100 kW of power. The turbine has been clocked at an even higher rate in Kotzebue's cold winds. NASA is also studying turbines that run in Antarctica, where the weather gets even colder.

Compared to the association's usual 66-kW models, the Northwind is "a much more complicated wind turbine" said Matt Bergan, a Kotzebue Electric Association engineer in charge of the wind program. "There's a lot more wiring, a lot more controls."

The new turbine, for example, relies on sensors that monitor the wind. Sensors transmit information to a motor, which then rotates the entire encapsulated turbine to face the wind.

NASA, the Department of Energy, and Northern Power Systems helped the Kotzebue Electric Association purchase the $250,000 prototype turbine. Kotzebue's other turbines cost about $75,000. NASA monitors the new turbine's functioning through a dedicated computer at the site.

 

The Mars wind moves a turbine only during dust storms. Solar power might pick up the slack during still times.

Though the Northwind is the same type of turbine that NASA scientists would like to locate on Mars, the 45,000-pound machine still remains prohibitively heavy, Bergan said. And that's not including the pilings, which at Kotzebue added another 10,000 pounds in weight. In Alaska, workers drilled the pilings into the permafrost. Because NASA estimates a cost of about $10,000 per pound to place a payload in low Earth orbit, the generator and tubular tower still remain far too heavy to ship to Mars. That doesn't deter Bubenheim, though.

"There's a lot of emphasis right now on developing lower-cost, heavy-mass launch vehicles," he said.

The jury is still out on how turbines would actually be sited on Mars.
Bubenheim isn't deterred by yet another fact about the Martian atmosphere. Data from the NASA Viking and Pathfinder probes show that the planet's ordinary surface winds don't blow strongly enough to drive wind turbines.

But those missions didn't visit the planet during a dust storm, he added. Computer models and wind tunnel tests show that dust storms are accompanied by extremely high winds that would be strong enough to drive turbines, even at the speed needed in the thin Mars atmosphere, Bubenheim said.

But wind turbine experts say that a special turbine design would be needed on Mars. Turbines need smooth blades to work efficiently and billowing dust could stick to blades or abrade them, said Alison Hill of the British Wind Association. The inner workings of a turbine generator would also have to be protected from dust clouds.

Special turbines developed for offshore use in the water might be studied, Hill said, because they demonstrate how turbines can be built or retrofitted to suit special needs.

"We've already shown that the technology can be altered for different environments," she said. "It's not inconceivable the same could be done even for an environment like Mars."

The genesis of the Cold Weather Wind Turbine project came when NASA scientists were studying wind generation at the U.S. Amundsen-Scott South Pole Station, a location that sees about six months of darkness each year, Bubenheim said. Scientists working on that project noticed the South Pole's atmosphere and conditions mirror Mars's. And the station mirrors Mars in more than just darkness. Residents remain at the station for a set amount of time and have to grow their own food and bring everything needed for their stay. The same, of course, would be true for those who inhabit a Mars space station. It's not feasible to ship diesel oil to the South Pole, and that is certainly also true of Mars, Bubenheim said.

"The South Pole station is a Mars analog," he said. "We were working with things like growing fresh fruits and vegetables, and recycling waste. Then we thought about using wind machines on Mars, too. People at both the South Pole station and a space habitat have to be careful to use electricity efficiently."

The key issue at the South Pole, in Alaska, and on Mars is maintaining the turbines in the extreme operating conditions, he added.

Wind turbines that generate energy to power a Mars space station may seem like science fiction, but to Bubenheim, Flynn, and other NASA scientists, it's a science fiction scenario that just might work.



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