Four astronauts were blasted into orbit aboard SpaceX’s Dragon capsule from Kennedy Space Center in Florida on Sunday night, marking the company’s first fully-fledged crewed mission to the International Space Station.
Mr Musk, who is usually present during major launches, could not attend after receiving two positive coronavirus tests and exhibiting minor symptoms of the virus.
Nasa rules forbid anyone from entering their facilities following a positive test, no matter what their position or role.
“When somebody tests positive for Covid, here at the Kennedy Space Center and across Nasa it is our policy for that person to quarantine and self isolate,” Nasa administrator Jim Bridenstine said ahead of the launch.
Mr Musk had previously questioned the legitimacy of the results, claiming that he had tested both positive and negative for Covid-19 on Thursday.
“Something extremely bogus is going on,” he tweeted. “Was tested for covid four times today. Two tests came back negative, two came back positive. Same machine, same test, same nurse. Rapid antigen test.”
He later tweeted that he “most likely" had a moderate case of coronavirus.
Some Twitter users mocked Mr Musk, noting that he had previously downplayed the seriousness of the coronavirus pandemic.
In March, Mr Musk declared that “the coronavirus pandemic is dumb."
Since then, nearly more than 11 million people have been infected and nearly a quarter of a million people have died from the virus in the US alone.
One Twitter user dubbed him “Space Karen” for his perceived indifference towards the pandemic, causing the term to trend across the platform.
Dr Emma Bell responded to his tweet by noting that rapid antigen tests only detect Covid-19 “when you’re absolutely riddled with it”.
She tweeted: “What’s bogus is that Space Karen didn’t read up on the test before complaining to his millions of followers.”