SpaceX has called on the Federal Aviation Administration to correct a report it submitted to Congress that warned that debris falling from U.S.-licensed low-Earth orbit (LEO) constellations could injure or kill someone every two years by 2035 if they occur as planned.

In an Oct. 9 letter from the FAA and Congress, Space News David Goldstein, SpaceX’s chief engineer, said the report was based on a “deeply flawed analysis” based on guesses, assumptions and outdated research. The letter arrived four days later Space News He contacted the company with questions about the report, which was posted Oct. 5 on the FAA’s website.

In the report, the regulator said 28,000 hazardous fragments from deorbiting satellites and the rockets that launch them could withstand re-entry every year until 2035, especially if SpaceX’s plans to rapidly expand Starlink go ahead.

As of 2019, SpaceX has launched 5,000 Starlink satellites, received approval from the US Federal Communications Commission to increase the number of Starlink satellites to 12,000, and is seeking international approvals to increase the number of Starlink satellites in orbit to 40,000. According to the FAA report, Starlink represents more than 85% of the expected risk to people on the ground and aviation from falling debris in the time period.

In 2020, Congress directed the FAA to issue a report on the risks associated with divesting satellites from LEO megasatellites. In 2021, the FAA tasked Aerospace Corp., a federally funded nonprofit focused on space, with providing a technical assessment of the growth of LEO constellations and the risks their unplanned and controlled reentry poses to aviation and people on the ground. satellites and the upper degrees that trigger them.

The FAA placed an order with Aerospace Corp. The focus is on geostationary satellites launched by the United States under FAA licenses, so the analysis excludes groups such as China’s proposed Guowang network of 13,000 satellites.

The aerospace company also concluded that there is a 0.0007 chance of a “plane crash” per year due to falling debris in 2035, which would likely kill everyone on board.

“By 2035, if the constellation is expected to grow and Starlink debris survives re-entry, the total number of hazardous fragments surviving re-entry is expected to reach 28,000 each year, and the expected number of casualties is also the projected number of people on Earth. Satellites ejected from these constellations will survive re-entry.” The rate of injury or death from remaining debris would be 0.6 per year, meaning that one person would be injured or killed on the planet every two years.

“Some debris also poses a danger to people on board. When we forecast global air traffic from 2019 to 2035 and assume that a piece of shrapnel that would injure or kill a person on the ground could also fatally damage an aircraft, the probability of a plane crashing (as stated in an aviation report) defined as a collision with an aircraft (object striking an aircraft) will be 0.0007 per year in 2035.” Excerpt from FAA’s Report to Congress: Risk Associated with Destruction of Satellites from Proposed Major Constellations in Low Earth Orbit

But the FAA acknowledged that if SpaceX was correct in reporting no surviving Starlink debris to date and its components were fragile enough to burn up completely in the atmosphere, “any increase in the risk of re-entry is minimal compared to the current risk.”

According to satellite tracker and astrophysicist Jonathan McDowell, 358 Starlink satellites have left orbit. There were no reports of their debris reaching the ground.

“To be clear, SpaceX satellites are designed and manufactured to completely fail atmospheric reentry at the end of their life and [виділення в оригіналі]Goldstein wrote in the letter.

“Extensive engineering analysis and real-world operational experience confirm this fundamental fact.”

He added that the FAA based its findings on the claim that the space industry has failed to achieve a 90 percent success rate in post-mission destruction, and said SpaceX’s post-mission destruction success rate exceeds 99 percent.

Goldstein also said the analysis misapplies a 23-year-old NASA study that found that about one piece of debris for every 100 kilograms of Iridium Communications satellites, a much smaller LEO constellation, survived reentry.

“The analysis cannot be applied to SpaceX’s satellites because—among other things—Iridium satellites were not even built for complete destruction” and “are unlike SpaceX or any other satellite in materials, design, construction, orbit, or operation,” he said. Modern satellite in LEO”.

The FAA was unable to comment because October 9 is a federal holiday in the United States.

Hard work

Precisely determining the risk of satellite reentry is difficult because of uncertainties in reentry survival calculations, Marlon, managing director of the Center for Orbital and Reentry Research, told SpaceNews on Oct. 5. Sorge .

“The phenomenology is quite complex and the available ‘basic’ data are limited,” Sorge said, and definitive conclusions also largely depend on the design of the satellites.

“As you can imagine, it is very difficult to obtain ‘basic’ data on what survives reentry by observing real-world reintroductions that occur randomly around the world, often in inappropriate locations,” he added.

Rather than trying to predict the future, he said, the analysis seeks to understand how behavior leads to the consequences of reentry so steps can be taken to reduce potential risks.

“Such information helps plan for possible future rule changes, taking into account possible future traffic increases,” he said.

According to Goldstein, Aerospace Corp made no attempt to review Starlink’s decommissioning analysis and “mistakes could have been avoided if Aerospace had simply conducted basic research on SpaceX, which it chose not to do.”

Goldstein also criticized Aerospace Corp. and for the FAA’s failure to update data in the 2021 constellation size analysis before submitting it to Congress.

While the report estimated that 54,902 FCC-licensed satellites were in space across 12 applications from nine operators, the updated regulations reduce that number to 7,518. In addition to excluding groups licensed by China and other foreign governments, Goldstein emphasized that the analysis did not take into account these satellites. US company Amazon plans to start launching the proposed array of more than 3,200 satellites next year.

“The FAA’s acceptance of the aeronautical report without questioning or reviewing raises concerns about the FAA’s technical ability to responsibly evaluate and regulate this area,” Goldstein wrote.

Missile fragment risk

The FAA report also highlights the increased risk of falling debris due to the increasing number of launches required to deploy and support large LEO arrays, in addition to returning satellites. U.S. commercial rockets launching large arrays often leave their upper stages in orbit, which have more mass than individual satellites and thus pose a greater re-entry risk to people on the ground.

The total mass of the 60 first-generation Starlink satellites is just over 17 tonnes, while the weight of the Falcon 9 booster that launches them to LEO exceeds 25 tonnes. The report also points to the re-entry of the Falcon 9 upper stage following the Starlink launch in March 2021, which “could land anywhere between 53 degrees south and 53 degrees north.”

Debris from the main stage of the China Long March 5B rocket, which re-entered Earth’s atmosphere two months later, caused widespread criticism in the United States and other countries. Although the debris fell into the ocean, since water covers 70% of the Earth, where most accidental entries occur, the FAA said there remains a risk of large objects re-entering populated areas.

“Despite guidelines recommending targeted reentry, large space objects reenter Earth’s atmosphere approximately once a week,” the report said.

“Some were introduced recently and many were introduced prior to any agreed disposal strategy.”

The U.S. government tracks reintroductions, but the FAA has said it cannot predict them accurately enough to provide meaningful warnings to those in danger.

“As a general rule, the return time may be inaccurate by up to ten percent of the remaining time in orbit,” the report warned. “This means that 10 hours before check-in, the estimated check-in time may be delayed by one hour.”

Goldstein’s letter to the FAA did not address the risk of injury or death from reentry missiles.

In September, the U.S. Federal Aviation Administration (FAA) issued draft rules requiring U.S. commercial launch providers to remove spent upper stages from orbit after launch, primarily to reduce the risks of orbital debris but also to limit risks to people on the ground from uncontrolled ignition. -inputs.

But the FAA has said it does not have the authority to adequately address risks associated with satellite constellations returning from LEO. The FAA’s rulemaking on the issue depends on whether other agencies (the FCC or the Department of Commerce) decide to initiate their own processes to regulate the return of Constellation-related debris.