Arnold AFB team conducts first test in specialized space chamber
By Philip Lorenz III , AEDC/PA
/ Published March 21, 2007
ARNOLD AIR FORCE BASE, Tenn. --
The U.S. Air Force's Arnold Engineer Development Center (AEDC) scientists and engineers are leading the way in finding solutions on Earth to complex problems satellites can encounter in space.
A team at the center's space chamber research lab has conducted the first system checkout for the lab's Characterization of Combined Orbital Surface Effects (CCOSE) Chamber in its most advanced configuration to date.
"Very few, if any, ground testing facilities have specialized space simulation chambers with the range of capabilities we've incorporated into this one at AEDC," said John Prebola, an Aerospace Testing Alliance (ATA) project manager at the space chamber research lab. "This chamber will save our customers money and help them provide reliable, long-term performance of systems that many of us rely on every day."
Tests conducted during the system checkout involved subjecting a solar cell and a sample of thermal control paint to conditions that are found in space.
The area above and beyond Earth's atmosphere is known to be punishing on components on the outer surface of satellites and other spacecraft orbiting Earth or transiting through the solar system.
These components, which include solar cells, thermal control surfaces and optics, require a clean environment to operate properly and continue to function. They are also vulnerable to factors such as charged particles, solar radiation, outgassing (release of gas from materials used to build satellite components) and contamination from thrusters.
"Even small amounts of contamination, solar radiation or atomic oxygen can seriously degrade the performance of these components and has caused multiple spacecraft (system) failures over the years," explained Dustin Crider, a physicist in ATA's Technology and Analysis Branch. "The more frequent problems we encounter in space are often due to a combination of these factors or what's known as a synergistic effect."
Air Force research Laboratory (AFRL), NASA and spacecraft manufacturers have a standard approach to space materials development.
"They create batches of new materials with varying characteristics and test how these materials respond to one or two aspects of the space environment at a time," Mr. Prebola explained. "These results are combined in computer models to predict how hardware built from these new materials will perform in space."
Limited ground tests are performed at different stages of the development cycle as hardware and subsystems grow in complexity and cost.
"Flight hardware is usually only tested for vacuum, vibration and thermal cycling due to the one-of-a-kind nature of the test article," he said. "AEDC is looking to improve the realism of ground testing and apply it throughout this development cycle. We want to insure the most reliable and survivable equipment is sent on what is typically a one-way trip to space."
Mr. Prebola described the current configuration of the CCOSE Chamber as a six-year endeavor.
"This chamber was designed, built and demonstrated in three years, but our focus has been on simulating low earth orbit - where the space shuttle and International Space Station orbit," he said. "Three more years have been spent expanding its simulation range to include geosynchronous earth orbit - where satellite TV and weather satellites orbit. It was recently upgraded to its current capability, allowing testers to subject space materials and hardware to either one or a combination of environmental effects that occur in space."
In addition to real-time orbital simulation, the chamber can simulate, in a condensed period of time, the long-term effects that the space environment will have on satellite hardware.
"We ran the first test of this newly configured system last May using thermal control paint that we had on hand," Mr. Prebola said. "The checkout test we completed in December 2006 was the first one involving organizations outside AEDC. Also, we added some electronics to evaluate the solar cell for that test."
The solar cell used in this test was developed by a company called Uni-Solar, but was sent to AEDC by Dr. Simon Liu of Aerospace Corp., at the request of John Merrill, chief of the Advanced Space Power Generation Group at AFRL's Space Directorate at Kirtland AFB, N.M. The thermal control paint came from Materials Analysis Program Manager 2nd Lt. Jered Fry, at the request of Capt. Norman Johns, both of whom are at AFRL's Directed Energy Directorate at Kirtland.