Elon Musk has hit back at criticism that his company's Starlink satellites were hogging up room in space, arguing that "tens of billions" of spacecraft could orbit close to Earth.
“Space is just extremely enormous, and satellites are very tiny,” Mr Musk said. “This is not some situation where we’re effectively blocking others in any way. We’ve not blocked anyone from doing anything, nor do we expect to.”
His comments, made in an interview with the Financial Times, came in response to a claim from Josef Aschbacher, head of the European Space Agency, that Mr Musk was "making the rules" for the new commercial space economy.
Speaking to the FT this month, Mr Aschbacher warned that Mr Musk’s rush to launch thousands of communications satellites would leave fewer radio frequencies and orbital slots available for everyone else.
SpaceX, Mr Musk’s private space company, has launched almost 2,000 satellites for its Starlink broadband communications network and has plans for tens of thousands more.
Rejecting suggestions he was “squeezing out” future satellite competitors, Mr Musk compared the number of satellites in low Earth orbit to what he said were 2 billion cars and trucks. Each orbital “shell” around the Earth is larger than the planet’s surface, he said, with an additional shell about every 10 metres further out into space.
“That would imply room for tens of billions of satellites,” he said. “A couple of thousand satellites is nothing. It’s like, hey, here’s a couple of thousand of cars on Earth – it’s nothing.”
Some experts challenged Mr Musk’s claim that satellites in low Earth orbit could safely match the density of cars and trucks on Earth.
Spacecraft travelling at 17,000mph need far greater separation than cars to leave time to adjust their orbits if a collision seems likely, said Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics. At that speed, a three-second gap would only leave room for about 1,000 satellites in each orbital shell, he calculated.
Potential collisions can only be identified close to when they might occur because of the difficulty of calculating the trajectory of many different satellites, which can be affected by changes in solar weather, Mr McDowell said.
“For many space users, planning an avoidance manoeuvre is at least hours if not days, so this suggests space is already too crowded,” he said.
China complained this month that two Starlink satellites had forced the country’s space station to take “preventive collision avoidance control” measures in October and July to “ensure the safety and lives of in-orbit astronauts”.
Laura Forczyk, a space analyst at space consulting group Astralytical, said Mr Musk's comparison of satellites to vehicles on Earth was "flippant", but added: "He's essentially correct that it's a traffic management problem." – Copyright The Financial Times Limited 2021