Renowned entrepreneur Elon Musk’s aerospace company SpaceX is no stranger to experiencing failures with its experimental Falcon-series of reusable launch vehicles, having previously lost one vehicle to an explosion during launch in 2015. But the cause of the catastrophic explosion of a Falcon 9 vehicle during a routine fueling operation on September 1 has investigators stumped, with Musk admitting that the investigation is "turning out to be the most difficult and complex failure we have ever had in 14 years." Musk has also stated that they are leaving no stone unturned in this investigation — including possible sabotage by external entities.

Video of the spectacular explosion shows an unknown object streaking horizontally from right to left across the frame as the Falcon 9 rocket explodes, prompting many UFO enthusiasts to speculate that this may have been an alien craft sent to destroy SpaceX’s launch vehicle. However, the object’s shape is not clear, so this could be any one of a large number of airborne objects, from a bird flying relatively close to the camera, to a drone bent on sabotage. When asked on Twitter about the possibility that the rocket was struck by something, Elon Musk replied that "We have not ruled that out."

While most launch vehicles that explode do so either during or after launch, Falcon 9 F9-029, carrying the Amos-6 communications satellite, exploded during a simple fueling operation. According to Tweets by Musk, "this happened during a routine filling operation. Engines were not on and there was no apparent heat source," meaning that there should have been no source of ignition to ignite the fuel.

Last year’s Falcon 9 explosion was due to the failure of an internal strut that allowed an "overpressure event" to occur in the liquid oxygen tank in the rocket’s second stage, causing it to explode. this might be a possible clue as to what happened on Sept 1, as the explosion originated in the same area of the craft. Musk also Tweeted: "Particularly trying to understand the quieter bang sound a few seconds before the fireball goes off. May come from rocket or something else." The rocket’s internal sensors so far have not shown anything amiss, so was this a repeat of last summer’s structural failure, or an explosion caused by sabotage?

The rocket’s payload was an Amos-6 communications satellite, owned by Israel’s Spacecom, with social media corporation Facebook leasing bandwidth on the satellite for internet communications with African businesses. Spacecom was due to be bought by China’s Beijing Xinwei Technology Group, provided the Amos-6 satellite successfully entered service — a deal that is unlikely to happen now.