His rocket had blown up into a spectacular fireball. The Cape Canaveral launchpad that SpaceX had essentially built from scratch was now in ashes. And Elon Musk was dumbfounded.

A week after the explosion in September 2016, with still no idea what caused the rocket to suddenly explode while being fueled ahead of an engine test, Musk vented on Twitter that the loss of the rocket was “turning out to be the most difficult and complex failure we have ever had in 14 years.”

On the Internet, where conspiracy theories were already percolating, some speculated that the “something else” was a projectile, maybe even a bullet or UFO. On Twitter, Musk was asked about the possibility of something hitting the rocket, and he fueled speculation even further by saying, “We have not ruled that out.”

Although they didn’t say so publicly at the time, SpaceX investigators were looking seriously at sabotage, Musk and SpaceX President Gwynne Shotwell said in their most extensive public comments since the explosion.

“We literally thought someone had shot the rocket,” Musk said in an interview last summer at SpaceX’s headquarters in Hawthorne, Calif. “We found things that looked like bullet holes, and we calculated that someone with a high-powered rifle, if they had shot the rocket in the right location, the exact same thing would have happened.”

If someone did shoot the rocket, SpaceX knew it needed to collect whatever evidence it could as fast as possible. “So for sure, we put pressure on the Air Force and the [Federal Aviation Administration] to go collect whatever forensic data was possible,” Shotwell said. “The first thing you do is think it’s some outside force, right. Because we couldn’t figure out how in the world this could have happened.”

Early indications were that something caused an upper-stage helium bottle to explode, and at the SpaceX test site in McGregor, Tex., engineers were trying to replicate the explosion. But “we were having a hard time blowing these bottles up,” she said.

So, instead, they got a rifle, “and we shot it,” Shotwell said. “And the signature on the bottle was just like the signature on the bottle that we recovered. That was an easy test to do. It’s Texas, right, everybody’s got a gun and you can blow stuff up.”

But who would want to?

About two weeks after the explosion, a SpaceX employee suddenly appeared at a Cape Canaveral facility of one of the company’s chief rivals. For years, SpaceX had been battling the United Launch Alliance, the joint venture of Boeing and Lockheed Martin, over lucrative contracts, worth hundreds of millions of dollars, to launch military satellites. At first, SpaceX was dismissed as an “ankle biter” and wasn’t taken seriously.

But SpaceX had become more successful than anyone predicted. It had also settled a lawsuit with the Air Force, which granted the company the right to compete against ULA. SpaceX now posed a serious threat.

The SpaceX employee who showed up at ULA’s facility had an odd request: Could he have access to the roof?

The reason, the employee explained, was that SpaceX had still images from a video that appeared to show a shadow, then a bright white spot, coming from the roof. ULA’s building was about a mile away from the launchpad and had a clear line of sight to it.

ULA was incredulous, and refused to let the SpaceX employee into the building. Instead, it called Air Force investigators, who inspected the roof and found nothing amiss.

It took months for SpaceX to complete its investigation into the cause of the explosion. Ultimately, it concluded there was a problem with a pressure vessel in the second-stage liquid oxygen tank. The FAA ruled out sabotage -- by rifle shot or any other means -- as a cause, and granted SpaceX a launch license so that it could return to flight.

Musk concluded that SpaceX, not ULA or anyone else, was to blame. “It was a self-inflicted wound,” he said in the interview. “It took us a long time, but we were able to re-create the failure.”

SpaceX returned to flight in early 2017. And then in February of that year, it had a triumphant launch in its first flight from the Kennedy Space Center’s launch pad 39A, the site that sent the crew of Apollo 11 -- Neil Armstrong, Buzz Aldrin and Michael Collins -- to the moon.

SpaceX pressed ahead, but Musk grew wary. Even if he had ruled out foul play, the incident “did alert us to the fact that sabotage was a real thing, so we upgraded security,” he said.

A few months later that security got a test.


A crew from CBS’s "The Late Show with Stephen Colbert," which was being escorted by Boeing officials, stopped outside the gates to check out pad 39A, SpaceX called security on them.

They were stopped and questioned. After showing identification, they were allowed to go.

This story is adapted from a forthcoming book, "The Space Barons: Elon Musk, Jeff Bezos and the Quest to Colonize the Cosmos."