The catastrophic issue, which was alluded to at the start of November, is said to have happened during the fuelling procedures. "I think we’ve gotten to the bottom of the problem," Musk told the broadcaster.
As the rocket was being loaded with oxygen – SpaceX mixes oxygen with liquid kerosene to fly – the propellant was too cold meaning it froze and caused the problem. Oxygen gaseous state freezes at −218.79 °C. The SpaceX boss said it was a "surprising" problem and one that has "never been encountered before in the history of rocketry".
SpaceX's rocket exploded on September 1 while it was preparing for launch at Kennedy Space Center, Florida. While nobody was injured in the blast, a satellite part-owned by Facebook was strapped to the rocket at the time and was lost in the fireball. Despite the problem, Musk said SpaceX launches could restart before the beginning of 2017.
Supercooled liquid oxygen that SpaceX uses as propellant actually became so cold that it turned into a solid. And that’s not supposed to happen.
This solid oxygen may have had a bad reaction with another piece of hardware — one of the vehicle’s liquid helium pressure vessels.
There’s speculation from the New York Times that if liquid helium was used in the pressure vessels, which Musk seems to have indicated, it might have been cold enough to freeze the liquid oxygen into a solid. Liquid helium exists at -452 degrees Fahrenheit, a lot colder than SpaceX’s liquid oxygen propellant at -340 degrees Fahrenheit. And oxygen solidifies at -361 degrees Fahrenheit.
SpaceX is confident about getting back to flight by the end of the year, based on what the company has found. And in a recent update, SpaceX claims to be focused on improving its helium loading processes so this accident doesn’t happen again.