“The micro-meteoroid impact experiment was going nowhere until we decided to shoot the multi-layer insulation, which serves as the thermal blanket covering a spacecraft and is composed primarily of plastics,” said Dr. Michael Starks, bench scientist and electronics engineer, Space Vehicles Directorate‘s Battlespace Environment Division, Hanscom Air Force Base, Mass.
“This is the type of material that is hit by micro-meteoroids in space so it made sense to apply it for the trial,” he said. “The projectile hit the target at 18 kilometers per second (43,000 miles per hour) and we saw fairly strong radio frequency emissions right at the moment of impact.”
Sparked from an idea discussed by a visiting Italian scientist in 2001, the micro-meteoroid impact experiment team took existing information on damaging milligram-sized pieces of carbon and other materials hitting spacecraft and focused on determining whether these same particles produce plasma which could ultimately cause communication interference.
Currently, micro-meteoroid detection on a satellite involves a small sheet of film, which creates a monitored electrical signal, but due to size constraints, impact coverage for the majority of the structure remains limited.
“If a satellite becomes inoperable today, the only way we know if it was a micro-meteoroid is though a diagnosis of exclusion,” Starks said. “If no other reason is found, then maybe it got hit.”
“Because of our dependency on space, it is critical to understand the effects of high-velocity impacts so we can operate effectively in the space environment,” he explained.
To replicate a micro-meteoroid impact on a spacecraft, experiment personnel partnered with Sandia National Laboratories’ Explosives Technology Group, which provided the hypervelocity launcher capable of shooting small titanium plates at speeds of 32,000 plus miles per hour.
For two weeks in May 2004, five shots penetrated an apparatus equipped with low and high frequency antennae, as well as a tungsten, and for the last four sessions, an indium target four inches wide.
Following the trials, researchers found plenty of radio signals produced by the projectile itself, but none originating from the impact. As a result of the failed tests, the experiment group headed back to the drawing board.