Pigs in Space: Cleaning the Celestial Junkyard
In April the International Space Station had to sidestep space junk twice in three weeks.
Photo courtesy of NASA
America has no ride into space at the moment other than with its estranged Russian space partners, but we can still address cleaning up the satellite-scattered trash heap in space, says a University of Alabama in Huntsville graduate student.
From the perspective of populated areas on Earth, big space junk is a worry.
“What we’re really concerned about is the big stuff that comes in uncontrolled and breaks up in the atmosphere into big chunks,” says Tom Percy. He is the primary author with his advisor, UAH Mechanical & Aerospace Engineering professor Brian Landrum, of a paper that outlines methods and policies that could be employed to mitigate space debris.
Larger objects are more likely to have parts survive re-entry, posing a potential risk to people on the ground. Think Skylab, big parts of which were strewn across Australia, if it had landed in New York.
But the biggest worry for satellites operating in orbit comes from the smaller debris, the stuff that’s 1 to 10 cm in size – from marble to softball-sized.
“We can’t see that stuff from the ground, we can’t see it with radar and we can’t see it with satellites,” Percy says. Yet small debris has the greatest potential to damage working satellites, rockets in flight or even the International Space Station.
In early April, according to news reports, the space station had to change position to avoid a space debris field of parts from an old Ariane 5 rocket launched by the European Space Agency that came within 1,000 feet of the ISS. It was the second time in three weeks the station had to sidestep space junk.
In 1978, NASA scientist Donald J. Kessler proposed a scenario now known as the Kessler Syndrome or Kessler Effect, where the density of space junk reached a point that collisions between objects would cause a cascade that would generate further debris to promote added collisions, potentially rendering space exploration unfeasible for generations.
In his paper, Percy outlines policy initiatives and engineering solutions that could prevent that tipping point from being reached.
“What we’re concentrating on now is the methods we can use to reduce space debris easier,” Percy says. “The work I’m doing for my PhD is how to deal with the problem through design modifications or additions before a space vehicle is launched.”
Working to equip future craft for their eventual removal could have a large impact, he says, because the size of the space community is growing quickly, from 16 nations two decades ago to 46 now. Engineering solutions for future spacecraft depend on type and size, as well as orbit. A deployable sail attached to a satellite could gradually slow it in low Earth orbit so it eventually burns up in the atmosphere. Or a small and light dedicated ion propulsion pack can nudge a craft into contact with the atmosphere.
“Implementing these engineering solutions on satellites before launch is becoming more critical in the burgeoning age of cube satellites, when scores of satellites can be launched from a single rocket,” says Landrum.
Pre-launch engineered solutions will probably have to be coupled with some form of active debris removal system to clear older debris and avoid the Kessler Syndrome, Percy says. “We’re investing some time and resources into active debris removal and how that can be accomplished now.”