A US daredevil pilot has been killed during an attempted launch of a homemade rocket in the Californian desert.

'Mad' Mike Hughes crash-landed his steam-powered projectile shortly after take-off.

The 64-year-old was well-known for his belief that the Earth was flat. He hoped to prove his theory by going to space.

His latest attempt was being filmed as part of a planned Science Channel show called Homemade Astronauts.

"Our thoughts and prayers go out to Mike Hughes' family and friends during this difficult time," the channel said in a statement.

"It was always his dream to do this launch, and Science Channel was there to chronicle his journey."

The launch intended to reach a height of about 1.5km - far below the 100km required to reach the edges of space. 

The rocket Hughes was in cost about US$14,000 to build. 

In a video posted to social media of the ill-fated launch, a parachute can be seen falling out of the rocket just after launch, leaving Hughes with no way of getting back to Earth safely. The rocket slams into the ground shortly afterwards, killing him on impact.

He managed to reach 570m in a launch last year, landing hard despite his parachute. 

"Am I glad I did it? Yeah, I guess. I'll feel it in the morning," he said at the time. "I won't be able to get out of bed. At least I can go home and have dinner and see my cats tonight."

Hughes wants to fly high enough so he can see the wall of ice flat-Earthers believe surrounds the planet, and take photographs of it. His rockets are emblazoned with phrases like 'research flat Earth'.

In 2017 he said he had no fears for his own safety.

"It's scary as hell, but none of us are getting out of this world alive," the former stuntman told AP of the experience.

"I like to do extraordinary things that no one else can do, and no one in the history of mankind has designed, built and launched himself in his own rocket."

In 2002 he reportedly set a world record for the longest jump in a limousine - 31m.