Amid accusations that SpaceX’s Starlink constellation is contributing to the space debris problem, including an estimate that up to three percent of the Starlink satellites might have ceased to function, SpaceX chief operating officer and president Gwynne Shotwell says that Starship could help to clean up dead satellites and spent rocket stages that are still in orbit.
“It’s quite possible that we could leverage Starship to go to some of these dead rocket bodies – other people’s rockets, of course – basically, pick up some of this junk in outer space. It’s not going to be easy, but I do believe Starship offers the possibility of going and doing that,” she told Time Magazine.
Space Debris a Problem for Space Operations
As early as 1978, aerospace officials and NASA scientists like Donald Kessler warned that space junk could cause a series of collisions that could severely damage the ability to make use of space-based capabilities like GPS, Earth observations, and communications satellites. Satellites typically orbit Earth at speeds of over 17,000 miles per hour and even the smallest ones can do serious damage to still-functioning hardware if they collide. This effect came to be known as Kessler Syndrome.
Kessler Syndrome was an important plot point in the movie Gravity, in which a fictional space shuttle was destroyed by debris. In the real world, the International Space Station has had to maneuver to avoid collisions with spent rocket stages and defunct satellites. The Federal Communications Commission has fined companies like Swarm for launching satellites without a permit out of concern that they could contribute to a Kessler Syndrome event that could damage satellites owned by other nations.
Some private organizations are already attempting to do something about the problem. A company known as D-Orbit, for instance, has proposed a reentry system called D-Sat that could be attached to satellites and used to deorbit them when they have reached the end of their useful lifespan. A demonstration mission for D-Sat was launched in June 2017.
How Could Starship Be Used to Reduce Risk of Kessler Syndrome?
Shotwell mentioned that Starlink is being launched into a lower orbit than most Internet satellites, which will make them easier to deorbit when they’ve reached the end of their useful lifespan. Because they are small enough to launch 60 at a time on a Falcon 9 and don’t come with heat shields, they are likely to burn up on reentry. This reduces the risk that debris from deorbiting satellites could cause property damage.
(It can happen if the reentering object is big enough. When NASA’s Skylab reentered, enough pieces of the space station fell on Australian soil for Australia to fine the United States for littering. Fortunately, there were no reports of injuries.)
Although SpaceX has launched nearly 900 Starlink satellites into orbit, it’s been estimated that only 820 of the satellites in orbit are still functioning because some have failed. This is enough to for SpaceX to launch public beta testing for its Internet service, but also enough to contribute to the space junk problem.
Could Starship be used to sweep up defunct satellites like the failed Starlinks or attach a reentry system similar to D-Sat? It’s possible, but might take a few years and probably isn’t a priority for SpaceX’s Starship program. Elon Musk said at the recent virtual Mars Society conference that Starship could reach Mars as early as 2024 even though SpaceX is still preparing for high-altitude tests of its Starship mock-up.
However, experts aren’t entirely ruling out the possibility that Starship could help with the problem.
“Starship could prove to be an important way to combat the threat of collision between massive space debris objects,” said Center for Space Standards and Innovation director Daniel Oltrogge. Pictures of the Starship spacecraft show “a substantial amount of cargo space, so the Starship vehicle could in principle facilitate Active Debris Removal (ADR) of many potentially large space objects.”