Volume 9, Number 5 • September/October 2001 • Small Business/SBIR

SBIR Inflatable Concentrator Tested for Space

EMRCE components set up in the GRC solar concentrator facility. Photo provided by Glenn Research Center.

Balloons in space may seem improbable, but researchers have just finished testing an inflatable solar concentrator system, using an SBIR-developed component, that will lead to just that outcome. The system and its variations—while orbiting Earth, sitting on the Moon or flying through space—will collect and concentrate sunlight or any other form of radiant energy for solar-power generation, thermal propulsion and even satellite communications.

The test is part of the Electro-Magnetic Radiation Control Experiment (EMRCE), a joint Air Force, NASA and industry effort to bring the technology to flight status within two years. The test took place in a solar simulator facility at the NASA Glenn Research Center, Cleveland, Ohio.

The facility is a large vacuum chamber fitted with a 288-kilowatt solar spectrum light source and liquid-nitrogen-chilled walls that can be cooled to temperatures approaching those experienced in space. The test simulated Earth-orbital conditions of Sun and shadow, first at room temperature and then at cold, space-like temperatures.

“The tests show that we’re on the right path toward flight capability,” said Wayne Wong, Glenn’s EMRCE test manager. “The concentrator performed within 10 percent of predictions and held its shape to within 0.8 mm. The focus controller, which had never been used in a vacuum before, performed remarkably well, and the rigidized, thin-film struts behaved as predicted.”

Several components were tested, including the SBIR-developed inflatable concentrator, a hexapod focus controller and inflatable, thin-film struts.

The inflatable concentrator is made of a thin, polyimide material that is already being used in space. It is formed with a transparent front canopy and an aluminum-coated rear reflector that takes on a dish shape when the concentrator is inflated. The concentrator was designed and built by SRS Technologies of Huntsville, Alabama, under an SBIR contract with Glenn.

The hexapod focus controller keeps the concentrator aimed at the Sun or other light source and holds the focal spot to a small area by adjusting the position of the concentrator. The focus controller was designed and built by ATK Thiokol Propulsion Corp. of Brigham City, Utah.

The inflatable, thin-film struts become rigid on inflation and exposure to ultraviolet radiation. To isolate their behavior, the rigidized struts were not attached to the other components for these tests. The struts were also manufactured by ATK Thiokol.

Inflatable systems have many potential advantages. On launch, they can be many times lighter than rigid concentrator systems. A very small volume, the size of an overnight bag during launch, could be inflated to the size of a basketball court in space. Inflation deployment is relatively simple and eliminates the need for mechanical actuators or human assembly. The low-mass, low-launch volume and simple deployment mean lower costs and greater safety.

Because solar concentrators can produce high temperatures (upwards of 2,000° K, 3,140° F), they may be the ideal heat sources for Stirling engines, which are very efficient at converting heat to electricity; for future thermal propulsion engines, which provide thrust by rapidly expanding a propellant at high temperatures; and for solar furnaces for materials processing in space. Although the tested system will concentrate sunlight, inflatable reflectors, or dishes, are also being designed for space communications antennas.

EMRCE is funded by the Air Force Research Laboratory’s (AFRL) Dual Use Science & Technology (DUS&T) office, Wright-Patterson Air Force Base, Ohio. Engineers from AFRL Propulsion Directorate at Edwards Air Force Base, California are providing technical oversight. Other partners in the industry and government EMRCE team are NASA Marshall Space Flight Center, Huntsville, Alabama; Boeing, Huntington Beach, California; and AFRL Space Vehicles Directorate, Kirtland Air Force Base, New Mexico. Q

For more information, contact Wayne A. Wong at Glenn Research Center, 216/ 433-6318 or wayne.wong@grc.nasa.gov Please mention you read about it in Innovation.

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