For Release: August 3, 2001
|Pamelia Caswell |
NASA Glenn Research Center
|Anne Gunter |
Air Force Research Laboratory (AFRL/PA)
|Paul Gierow |
|Rod Bitz |
Alliant Techsystems Inc
Balloons in space may seem improbable, but researchers have just finished testing an inflatable solar concentrator system 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 Electromagnetic Radiation Control Experiment (EMRCE), a joint Air Force, NASA, and industry effort to bring the technology to flight status within 2 years. The test took place in a solar simulator facility at the NASA Glenn Research Center, Cleveland, OH.
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."
The components tested were
An inflatable concentrator made of a thin, polyimide material that is already being used in space. The concentrator 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, Hunstville, AL, under a Small Business Innovative Research contract with Glenn.
A hexapod focus controller that keeps the concentrator aimed at the Sun (or 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., Brigham City, UT.
Inflatable, thin-film struts, that on inflation and exposure to ultraviolet radiation become rigid. The rigidized struts were not attached to the other components for these tests so their behavior could be isolated. The struts were also made by ATK Thiokol.
Inflatable systems have many potential advantages. On launch they can be many times lighter than rigid concentrator systems. A quite small volume, on launch the size of an overnight bag, in space could be inflated to the size of a basketball court. 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 2000 K, 3140 °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, OH. Engineers from AFRL Propulsion Directorate at Edwards AFB, CA, are providing technical oversight. Other partners in the industry and government EMRCE team are NASA Marshall Space Flight Center, Huntsville, AL; Boeing, Huntington Beach, CA; and AFRL Space Vehicles Directorate, Kirtland AFB, NM.
Glenn, for 60 years one of the Nation's leading federal research laboratories, has conducted cutting-edge energy conversion research since the 1950s.
For more information about the individual technologies and programs, see
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Print quality images are available at http://www.grc.nasa.gov/WWW/PAO/pressrel/2001/01-062addm.html
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