SAN FRANCISCO — Alliant Techsystems (ATK) is proposing plans for a small satellite designed to address one of the most vexing problems facing spacecraft operators in low Earth orbit: debris too small to be tracked by ground-based telescopes but large enough to penetrate satellite shielding.
The plans, which are scheduled to be discussed publicly for the first time Aug. 11 at the small satellite conference sponsored by the American Institute of Aeronautics and Astronautics and Utah State University in Logan, Utah, calls for development of a spherical spacecraft enclosed in multiple layers of a lightweight material. The spacecraft would operate in low Earth orbit as a sweeper or shield, breaking up debris particles and reducing their velocity, according to Jose Guerrero, chief technologist for ATK Spacecraft Division’s Systems and Advanced Technology Group in Pasadena, Calif., one of the chief architects of the new satellite.
A piece of debris measuring 10 centimeters in diameter, for example, would break when it hit the outside layer of the sphere and become progressively smaller as it passed through multiple layers of material, Guerrero said. Inside the sphere, that debris also would collide with other pieces of debris, causing each one to shatter again. The goal is to turn large debris particles that pose a threat to spacecraft into much smaller pieces that can be deflected by exterior shielding. By causing that debris to lose velocity, the spherical satellite also is designed to make those particles deorbit more quickly than they otherwise would, Guerrero said.
Guerrero declined to discuss the material ATK engineers plan to use for the multilayered sphere. In testing and simulation, an aluminum mesh was used to demonstrate the concept, according to the ATK report scheduled to be released at the conference in Logan, titled “How Can Small Satellites be used to Support Orbital Debris Removal Goals Instead of Increasing the Problem?”
ATK officials began seeking solutions to the problem of orbital debris shortly after a Chinese anti-satellite weapon destroyed a retired Chinese weather satellite in 2007, creating thousands of additional pieces of debris in low Earth orbit. A group of ATK scientists and engineers became so interested in the issue that they began meeting regularly over lunch to discuss the issue of debris and to seek potential solutions. “Engineers love to work on a complex problem,” Guerrero said. “This is an opportunity to resolve this issue. This issue is not going away. It’s going to get worse.”
During those meetings, ATK scientists and engineers evaluated many possible techniques for eliminating debris, including ground-based and space-based lasers, considering each concept’s relative merits, Guerrero said. After a thorough analysis, the multilayered sphere “happened to be the one with the most promise” and “the only one that could be used on a small satellite,” he said.
The small satellite would weigh approximately 500 kilograms and have roughly three kilowatts of onboard power, according to the ATK report. ATK officials have discussed the spherical satellite proposal with officials from the U.S. Defense Advanced Research Projects Agency (DARPA), the U.S. Air Force and NASA, Guerrero said. Further development of the concept, including testing, will require government funding, he added.
Since the Chinese anti-satellite test and the subsequent collision of a retired Russian Cosmos satellite with an active Iridium mobile communications satellite, NASA and the Defense Department have focused increased attention on the issue of orbital debris. In December, DARPA and NASA held the first international conference to explore solutions to the problem of orbital debris. In addition, the White House’s national space policy issued June 28 calls on NASA and the Defense Department to “pursue research and development of technologies and techniques … to mitigate and remove on-orbit debris, reduce hazards, and increase understanding of the current and future debris environment.”
The U.S. Air Force relies on ground-based radar and telescopes to track debris measuring 10 centimeters or larger. The Air Force issues warnings to satellite operators when their spacecraft may be in the path of debris, giving them time to maneuver away from the danger. Smaller debris, however, often hits satellites without warning. “Every spacecraft, whether manned or unmanned, is vulnerable to debris larger than 1 centimeter,” according to Nicholas Johnson, NASA’s chief scientist for orbital debris at the Johnson Space Center in Houston.
Orbital debris measuring between 1 and 10 centimeters in diameter also poses risks to the international space station, which features exterior shielding to guard against damage from debris smaller than 1 centimeter. While the ATK proposal is designed to address the overall threat of debris in low Earth orbit, the spherical satellite also could be used to protect specific assets. “You could deploy it around the space station and clean up that area,” Guerrero said.