NASA has written a letter to the US federal government raising concerns about SpaceX’s proposed second-generation Starlink mega-constellation of 30,000 satellites.

In the five-page page letter to the Federal Communications Commission (FCC), NASA argues that SpaceX’s plans to fill the skies with thousands more Starlink satellites could lead to a “significant increase” in potential collisions in low Earth orbit, as well as interfere with their science and human spaceflight missions.

Starlink is a constellation of internet satellites operated by SpaceX that “beam down” broadband internet across the globe. While expensive, it's particularly useful at providing high-speed internet to people who live in rural areas where conventional internet access is poor. The aerospace company has previously received authorization to launch approximately 12,000 satellites, but has since requested authorization for a second-generation constellation of 30,000 satellites. 

NASA says this expansion would double the number of tracked objects in Earth’s orbit and increase the number of objects below 600 kilometers (372 miles) over five-fold. This, they argue, is an accident waiting to happen. 

“An increase of this magnitude into these confined altitude bands inherently brings additional risk of debris-generating collision events based on the number of objects alone,” the letter reads. “NASA anticipates current and planned science missions, as well as human space flight operations, will see an increase in conjunctions.”

The letter also refutes SpaceX’s claim that collisions are not a worry as the satellites can auto-maneuver out of the way, saying this point isn’t backed up by “statistical substantiation.”

NASA’s letter of concern comes the week after SpaceX launched 49 satellites and lost 40 of them after a geomagnetic storm hit Earth the day after launch, sending the satellites burning down into the atmosphere.

Many have also expressed concerns about overcrowding in low-Earth orbit and the mega-constellation before. Some estimates suggest that SpaceX Starlink satellites are responsible for up to half of close encounters in orbit.

However, Elon Musk – founder and CEO of SpaceX – denies there’s a big issue, comparing the impact of his Starlink fleet to “a couple of thousand cars on Earth.”

“Space is just extremely enormous, and satellites are very tiny,” he told the Financial Times last year. 

Even beyond the issue of satellite congestion, Starlink’s satellite constellation has sparked controversy. Many astronomers, astrophotographers, and satellite operators have complained that the thousands of satellites are filling up the skies and hampering their ability to observe, and photograph, the night sky. With 30,000 more satellites up there, things are only set to get more congested. 

[H/T: Jeff Foust, the aerospace journalist who uploaded the document to Scribd]