“Space junk” is seen as a serious issue in the space business. With so many satellites in orbit, there is an ever-growing risk that a “dead” satellite or spent rocket stage will collide with active satellites. The International Space Station has had to maneuver to avoid collisions with space junk that could have been catastrophic in an environment where everything moves fast enough for E = MC2 to be a serious variable.
This was a major plot point in the movie “Gravity,” in which a cascade of collisions between objects in space destroys a space shuttle and two space stations. Experts say that the astrodynamics involved were not very realistic, but space junk is still a concern in increasingly crowded Earth orbits.
Several aerospace insiders have proposed methods to dispose of “space junk” once it has reached the end of its useful life. This includes D-Sat’s test of a “retro-rocket” system that can be used to slow a non-functional satellite down enough for it to deorbit and burn up in the atmosphere. The retro-rocket would be able to function independently of the satellite. If a system similar to D-Sat’s becomes the norm, it could greatly reduce the risk that a defunct and uncontrollable satellite could collide with valuable live hardware.
The space junk issue is the topic of a current spat between SpaceX and ViaSat with the Federal Communications Commission acting as a mediator. ViaSat has filed a regulatory challenge accusing SpaceX of ignoring environmental concerns, including adding to the potential of basically “littering” space with thousands of defunct satellites as the Starlink satellites become non-functional. Elon Musk, of course, fired back that ViaSat, which has launched its own Internet satellites, is more worried about the competition than anything else.
Astronomers and astronomy hobbyists have also complained about strings of visible Starlink satellites ruining their viewing. Even with the shades that SpaceX is now adding to new satellites, astronomers say that they can interfere with data collection for astronomy-related studies.
Now SpaceX and NASA have announced a deal to keep the risk of space collisions as low as possible — a timely announcement, considering that SpaceX has launched a little over 1,000 of a planned 42,000-satellite constellation for its Starlink Internet service. The deal requires that SpaceX take steps to minimize the risk that one or more of those satellites might collide with somebody else’s valuable space hardware.
This includes giving Starlink satellites the ability to evade a collision with NASA’s hardware when necessary. SpaceX will also time the launch of new satellites to minimize the risk of collision with the International Space Station.
NASA refers to this agreement as a “reimbursable agreement” in which no money changes hands, but both parties reach a deal in which each gets something they want. The current deal gives NASA the authority to negotiate future agreements that protects NASA’s current and future operations. It also acknowledges that SpaceX is in a unique position and provides for the sharing of information that could impact the operations of either or both parties. The text of the agreement can be found here.