The launch pad explosion last week that destroyed a SpaceX rocket and a communications satellite is turning out to be the "most difficult and complex failure" in the company's 14-year history, Chief Executive Elon Musk tweeted early Friday morning.
In a series of tweets, Musk shared some details about the ongoing investigation into the fiery accident, which occurred Sept. 1 at Cape Canaveral Air Force Station in Florida.
The explosion occurred as the Falcon 9 rocket was being fueled for a standard static fire test ahead of an expected launch on Sept. 3. SpaceX said last week that data indicated the "anomaly" originated around the upper-stage liquid oxygen tank.
No one was injured in the explosion, though it destroyed a $200-million communications satellite that was set to play a key role in Facebook's plans to provide Internet access to remote villages in Africa.
Musk said Friday morning that the engines were not being fired at the time and that there was "no apparent heat source."
The company, he said, is especially interested in "trying to understand the quieter bang sound a few seconds before the fireball goes off," he tweeted. "May come from rocket or something else."
When a Twitter user asked whether "something hit the rocket," Musk tweeted, "We have not ruled that out."
The Federal Aviation Administration is overseeing the investigation into the incident, and NASA, the U.S. Air Force and other industry experts also are participating.
Under federal law, SpaceX is allowed to conduct its own investigation. SpaceX, whose full name is Space Exploration Technologies Corp., and other companies lobbied successfully to extend the law last year.
Last week, SpaceX said it was "in the early process of reviewing approximately 3,000 channels of telemetry and video data covering a time period of just 35-55 milliseconds."
Musk asked Twitter followers to email any recordings of the explosion to the Hawthorne company.
Last week, analysts said the fact that the explosion occurred before launch would narrow the search for causes, making the investigation potentially less complicated than the postmortem after SpaceX's last launch failure in June 2015. In that incident, a Falcon 9 rocket laden with supplies for the International Space Station disintegrated minutes after liftoff.
Musk's tweets about the investigation are "unusual," as most companies would prefer to stay quiet until a likely cause has been identified, said Phil Smith, senior space analyst for the Tauri Group, an aerospace consulting firm.
In this case, Musk might be trying to show the world that the company is "on top of things," he said.
"When things are very quiet, people wonder what's going on," Smith said. "It does look like he's seeking mainly more data."
Such candor has made Musk famous, but Smith said his unfettered approach "presents certain challenges from a public relations or communications view." That's why few executives would risk describing the cause of a high-profile accident as enormously difficult to determine, or respond to social media speculation.
Marco Caceres, senior space analyst at the research firm Teal Group, said Musk's tweets illustrate the company's more informal corporate culture, which has helped win SpaceX popular support.
"Generally executives from big corporations are not that transparent," he said. "They're much more guarded in the words that they use."
Musk can afford to be more open because SpaceX is a private company and doesn't have to answer to shareholders, Caceres said.
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3:10 p.m.: This article was updated to include comments from space analyst Marco Caceres.
2:17 p.m.: This article was updated to clarify language.
1:05 p.m.: This article was updated with comments from aerospace analyst Phil Smith.
12:05 p.m.: This article was updated with additional comments from analysts on how Elon Musk's tweets reflect on SpaceX.
9:25 a.m.: This article was updated with additional information about how accident investigations are handled.