SpaceX: Actually, Dying Starlink Satellites Don't Always Fully Burn Up

upstart writes:

SpaceX: Actually, Dying Starlink Satellites Don't Always Fully Burn Up:

SpaceX is warning that retired Starlink satellites might not always fully disintegrate upon re-entry into the Earth's atmosphere. Small remnants may survive and land on the ground.

The company made the statement on Thursday as SpaceX has been de-orbiting and retiring hundreds of older Starlink satellites by plunging them back into the Earth's atmosphere, which should incinerate the hardware. All Starlink satellites were designed to orbit for about five years.

SpaceX has previously said that Starlink satellites have been engineered to "fully demise" during atmospheric re-entry, thus posing no threat to the public. But in Thursday's statement, the company said small fragments from the burning debris can continue to fly toward Earth.

Still, the company maintains that satellite debris poses no danger. For example, the chance of the company's newest Starlink satellites causing human harm has been rated at "less than 1 in 100 million, significantly more conservative than the current industry standard."

It's unclear if the risk is higher for older Starlink satellites launched five years ago. But SpaceX says it adopted a "more conservative approach" than current US regulations, which require operators to keep the risk levels of falling space debris from causing a human casualty to under 1 in 10,000.

Although the company's newest V2 mini Starlink satellites should disintegrate if they're sent burning through the atmosphere, SpaceX also noted: "We predict that approximately 5% of the mass of the entire satellite could survive reentry."

"The biggest contributor (~90% of the surviving mass) is silicon from the solar cells, which has a high melting point and a very low ballistic coefficient, which could survive reentry in extremely small fragments," the company added. That said, if any silicon fragments survive, they will end up landing on Earth with less than one joule of energy - or about how much energy it takes to lift an apple.

While the falling silicon debris should be harmless, SpaceX noted that the magnetic ceramic materials in "the core of inductors and transformers" of a Starlink satellite can also survive re-entry. As a result, the company says it is "limiting the size and the mass of each inductor core, even at the cost of reducing their efficiency and increasing the complexity of the system design."

In one rare instance, the company also revealed that "a 2.5 kg piece of aluminum" found on farm grounds in Saskatchewan, Canada, was traced to a Starlink satellite. Specifically, the surviving aluminum came from "a modem enclosure lid of the backhaul antenna on a Starlink direct-to-cell satellite, SpaceX said. That aluminum part was supposed to disintegrate during re-entry.

But the 5-pound metallic part likely survived because the satellite had failed to properly de-orbit. The satellite was among 20 Starlink satellites launched in July that later fell back to Earth due to a malfunction during launch. "Learnings from this event were quickly incorporated into the design of the V2mini optimized satellite," the company added.

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