Commercial rocket company SpaceX has said that it has found the fault that caused the failure of its third launch on Saturday.

The problem occurred with a new engine the two stage rocket was using, which uses a new kind of cooling system. The result was that fuel remained in the pipes and the engine burned for an extra 1.5 seconds after separation, pushing it back into the second section.

The rocket then fell into the Pacific Ocean and was destroyed, along with its payload of three satellites and the ashes of 208 people, including those of James Doohan, better known as 'Scotty' from Star Trek.

Elon Musk, founder of SpaceX and former founder of PayPal, was robust in his commitment to the project in an interview with Wired.

"Optimism, pessimism; we're going to make it happen," he said.

"As God is my witness, I'm hell-bent on making it work."

He said that the fault would be very easy to fix and the company would launch as soon as the next rocket was ready, later this year.

SpaceX has also received an extra $20 million in funding from Founders Fund, a $220 million venture capital firm managed by his fellow PayPal co-founders.