News

Protective ‘Skin’ Could Herald Tiny Satellite Fleet

By Irene Klotz
Discovery News
September 5, 2008
Dr. Douglas Lemon

Adaptable Coating
A new technology, called electro-chromatic film, turns spacecraft skin into a heat-regulating system by shifting its color when an electric current passes through. With a positive charge, the coating darkens and can absorb heat from the sun. A negative voltage lightens the shade, increasing its reflectivity. (Prasanna Chandrasekhar)

In what could be a big breakthrough for tiny satellites, a team of researchers has created a thin plastic–like coating that can switch from cooling to warming with a quick pulse of electricity.

The technology, announced at the recent American Chemical Society annual meeting, addresses one of the chief hurdles of developing small spacecraft that are inexpensive to build, launch and operate in orbit.

The problems are complex. Not only do satellites have to operate in a schizophrenic range of temperatures — it is blisteringly hot in the sun and approaching absolute zero on the dark side -- they must rid themselves of heat generated by their own electronics.

Larger satellites can do this with mechanical louvers, which operate like window blinds to control how much heat is release or retained, but the devices are inefficient for small satellites.

Government, military and commercial satellite operaters have been eying micro- and nano-sized craft weighing between two and 100 pounds or so as a quick and relatively inexpensive way to get remote sensors and imaging systems into orbit.

"The trouble with small satellites is that there is not a lot mass and power to devote to thermal control," said Quinn Young with Utah State University's Space Dynamics Laboratory. "You basically are trying to stick just your instruments and your electronics into space."

The new technology, called electro-chromatic film, turns the spacecraft skin into a heat-regulating system by shifting its color when an electric current passes through. With a positive charge, the coating darkens and can absorb heat from the sun. A negative voltage lightens the shade, increasing its reflectivity.

"It's kind of like a winter coat," explained Young. "When the sun is shining you open it up, in the shadows you zip up in an attempt to keep your temperature stable."

The technology has been used for terrestrial applications, including windows on high-end automobiles, but is fairly new to the aerospace industry.

"It's really hard to get technology demonstrated sufficiently for putting on a spacecraft," Young said. "You have to go through lots of tests and analysis on Earth because it's so hard and so expensive to get spacecraft into orbit."

Still to be determined is how the skin fares in the radioactive environment of space, where free-floating atomic oxygen and ultraviolet rays break down molecules.

"It's revolutionary in the sense that we've never had the capability to regulate how much heat we lose, other than the louvers. These electro-chromatics, in the next several years as they are proven, give us an ability to control the temperature of the spacecraft by radiation.

Prasanna Chandrasekhar, with New Jersey based Ashwin-Ushas Corp., is the lead researcher on the project, which is being developed in partnership with NASA.