The question was raised by the FAA, the Federal Aviation Administration that regulates private launches in the United States: Space debris will become increasingly plentiful as it falls back to Earth and resists re-entry into the atmosphere. Consequently, the risk of a collision with a commercial aircraft is higher. The conclusions about this deadly risk are disputed by SpaceX. Futura takes stock with Pierre Omaly, space debris expert at Cnes.
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This is another alarming report about the space debris situation. We have known for a long time that their numbers will continue to increase. For information: The European Space Agency (ESA) catalogs more than 36,500 pieces of debris measuring more than ten centimeters in low orbit and estimates that there are almost a million pieces measuring between one and ten centimeters.
Problem that was previously an exceptional case
The FAA (Federal Aviation Administration) report released today, September 22nd, warns of the decay of debris and abandoned satellites in our atmosphere. Due to their speed, their penetration into the air causes such great friction that decomposition is almost complete. Nearly. Only a few pieces of debris survive the crossing and fall back into our lower atmosphere and then to the ground. We generally worry when large structures enter our atmosphere. For example, we still remember the uncontrolled re-entry of the first stage of the Chinese Long March 5 rocket, which led to the precautionary closure of several airspaces in southern Europe. But as the European Space Agency points out, the amount of debris returning to our atmosphere is already increasing.
0.84% chance of impact in 2035
Fortunately, most debris that passes through our atmosphere has a high chance of falling back into the seas or oceans. But as in the Long March 5 example, their crossing can lead to the closure of airspace to avoid even the slightest risk of collision.
According to the report, the risk of collision between an aircraft and debris flying through the lower atmosphere, currently estimated at 0.01%, will increase to 0.84% in 2035. A sharp climb that shouldn’t be taken lightly, but realistic? “The report was originally written by The Aerospace Corporation, a company well versed in the problem of debris re-entry and with many years of experience,” Pierre Omaly, space debris expert at Cnes, told Futura.
The reason given is the current and future increase in the number of satellite disintegrations in the atmosphere. Recently, SpaceX launched its 5,000th satellite into orbit, while Amazon just deployed the first two pioneer satellites of its Kuiper mega-constellation of more than 3,400 satellites.
SpaceX’s counterargument
Is the FAA report based on outdated technology? Pierre Omaly tells Futura: “This report is based on projections of the situation as we know it today.” They used what they knew about atmospheric reentry, things they actually saw. And the items found on the ground are not numerous. This is especially true for Iridium satellites [constellation de communication, NDLR], where we know that when a satellite returned, a tank reached the ground. They started from this hypothesis and assumed that all satellites were like that because those are the only facts we have today, and then they came up with rules of three.
This supposedly incomplete disintegration is disputed by SpaceX in a letter to the US government, claiming that Starlink satellites are designed to completely disintegrate in the atmosphere without producing debris. Starlink program lead engineer David B. Goldstein says that none of the 325 Starlink deorbits conducted since February 2020 have produced debris. “We can only trust them because we don’t have access to their documents,” explains Pierre Omaly. It’s still possible, but I’m very curious about the solutions they used because it’s a real challenge. »
While the report describes the proportion of controlled satellite re-entries into the atmosphere at almost 90%, SpaceX claims to achieve 99%. Another argument from SpaceX: in the report, the estimated number of satellites in orbit in 2035 takes into account the full deployment of 30,000 Starlinks, while the number approved by the FCC (Federal Communications Commission) today is 7,518. Funny argument considering SpaceX intends to deploy 30,000 satellites. In addition, last week SpaceX submitted an application to the International Telecommunications Union (ITU, branch of the United Nations) to use frequencies… for 29,988 satellites!
And as for regulation?
With OneWeb, Kuiper or even Chinese mega-constellation projects, the number of satellites in low orbit will be extravagant. Will they all completely decay in the atmosphere? In any case, on the French side, this will soon be enforced, as Pierre Omaly reminds us: “As the Space Operations Law evolves (scheduled for publication in early 2024), this point will be specifically written.” It is required that the overall risk of a constellation for the population must not be larger than 0.0001%. The entire constellation must be completely destroyed during atmospheric re-entry.”