“It’s all happening really fast,” Victoria Samson, chief director of space security and sustainability for the Secure World Foundation, said in an interview.
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Samson said that, currently, there is a fairly large “bubble” around satellites when it comes to collision detection. This is due to uncertainty in the exact location and movement of vehicles. If you improve space situational awareness, like what SpaceX wants to do with Stargaze, those bubbles can be made smaller to reduce the number of potential collision warnings. But it will come with risks.
“Of course, there’s a lot of room in space,” Samson said. “But the question is, how much risk are you willing to take?”
Marlon Sorge, a technical expert at the aerospace corporation, told Ars that many unanswered questions about SpaceX’s proposed megaconstellation for orbital data centers make it difficult to assess collision risks. This includes their size (they would require very large solar arrays to collect sunlight) and precisely where the satellites would be deployed. There is already plenty of debris about 800 to 1,000 km above Earth from previous collisions, including the infamous Chinese anti-satellite missile test in 2007, which created more than 3,000 pieces of golf-ball-sized or larger debris.
Above that height, there is less debris, Sorge said. But objects at that altitude take centuries to naturally exit orbit due to the very limited atmosphere.
“The big challenge at those heights is that the stuff that’s there stays there,” Sorge said. “If you generate more debris, if you have problems, it won’t go away, so you’ll be stuck with it.”
SpaceX sought to address these concerns in its regulatory filing, noting that each satellite would have “redundant maneuverability capabilities” to move out of orbit into Earth’s atmosphere. The filing also recognized emerging science that indicates that aluminum burning from re-entry satellites is harmful to ozone levels. To address this, SpaceX is considering moving older satellites into “high altitude Earth orbits or heliocentric orbits”.
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