Tragedy of the Commons: Low-Earth Orbit Unusable in 10-15 years ...Amazon Reports Collision Risk for Mega-Constellation of Kuiper Internet Satelliteshttps://spectrum.ieee.org/tech-talk/aerospace/satellites/amazon-reports-collision-risk-for-its-megaconstellation-of-kuiper-internet-satellitesLast month, Amazon provided the U.S. Federal Communications Commission (FCC) with data for its planned fleet of 3,236 Kuiper System broadband Internet satellites.
The filings lay out a plan to put 3,236 satellites in low Earth orbit — including 784 satellites at an altitude of 367 miles (590 kilometers); 1,296 satellites at a height of 379 miles (610 kilometers); and 1,156 satellites in 391-mile (630-kilometer) orbits.
If one in 10 satellites fails while on orbit, and loses its ability to dodge other spacecraft or space junk, Amazon’s figures [PDF] show that there is a 12 percent chance that one of those failed satellites will suffer a collision with a piece of space debris measuring 10 centimeters or larger. If one in 20 satellites fails—the same proportion as failed in rival SpaceX’s first tranche of Starlink satellites—there is a six percent chance of a collision.
Those figures are not even the worst case scenario. The FCC also asked Amazon to provide an aggregate collision risk should 15 percent of its satellites lose their ability to maneuver. That resulted in a 17 percent chance of a collision.More than a third of all the orbital debris being tracked today came from just two collisions that occurred about a decade ago. Researchers are concerned that more explosions or breakups could accelerate the
Kessler Syndrome—a runaway chain reaction of orbital collisions that could render low earth orbit (LEO) hostile to almost any spacecraft. “Six percent is huge,” says John Crassidis, an expert on orbital debris at the University at Buffalo. “At a six percent chance of collision, astronauts would be put into an escape hatch to possibly escape. Even at orders of magnitude less than that, you’d want to do a maneuver to avoid it.”
... When responding to the FCC in 2017, SpaceX only provided a collision risk for the one percent failure scenario - it's already had a 5% failure rate - , writing [PDF]: “SpaceX views satellite failure to deorbit rates of 10 or 5 percent as unacceptable, and even a rate of 1 percent is unlikely.”
... three out of 60, or five percent, of the SpaceX's first batch of Starlink satellites failed following their launch in May
Even higher failure rates than 15 percent are not unheard of. Around 30 percent of Iridium’s first generation of communication satellites died on orbit, and the European Space Agency noted in its latest space environment report [PDF] that only about half of all satellites are properly disposed of at the end of their lifetimes.
If the risk associated with a one percent failure rate that SpaceX quoted is extrapolated to a 15 percent failure rate, Elon Musk’s satellites presented a similar aggregate risk as those belonging to Jeff Bezos, at around 14 percent. However, SpaceX has since altered its planned operational altitude for these satellites, and made design changes, which could reduce the chance of collisions. The company does not seem to have supplied the FCC with updated collision risk figures for its new working altitude of 550 kilometers, which is close to Amazon’s.
... In December, IEEE Spectrum reported that the aggregate chance that SpaceX’s planned Starlink constellation would cause an injury or death on Earth was 45 percent every six years.