'Mad' Mike Hughes is believed to possibly be dead after launching himself in the air with a self-made rocket that crash-landed -- and it was captured on camera.

The well-known daredevil and amateur rocket-engineer was doing a rocket launch Saturday in what appears to be near Barstow, CA -- where a reporter says Mike propelled himself into the air with a "self-made steam-powered rocket" and then crash-landed into the ground.

The reporter, Justin Chapman, adds, "Very likely did not survive." He tells TMZ ... Mike is confirmed to be dead there on the ground as well.

In the video, you see a parachute fly out of the rocket, but it doesn't appear anyone is using it. The presumption, for now, is that Mike might've stayed in the rocket as it ascended hundreds of feet into the air.

Mike's rep, Darren Shuster, tells TMZ he was NOT at the launch Saturday, but does believe his longtime client to be deceased based on what he's seen and heard. Darren says Mike was a "one-of-a-kind" adding, "When God made Mike he broke the mold. The man was the real deal and lived to push the edge. He wouldn’t have gone out any other way! RIP"

For Saturday's experiments, Mike is said to have been attempting to get as close to space from Earth as possible -- otherwise known as the Karman line, about 62 miles above Earth's surface -- without the use of advanced tech you might find at NASA or SpaceX.

Much more tragic, Mike seemed pretty stoked for the launch this weekend. He posted a video describing his rocket, where it would go down and what he was aiming to achieve. BTW, he was a big flat-earth believer -- and a doc was even made about him trying to prove it.

We've reached out to the San Bernardino County Sheriff's Dept. for comment ... so far, no word back. However, we were told by a dispatcher at the Victor Valley Sheriff's Station that a call for service had been placed Saturday out of Barstow -- the nature of which is unclear.

Mike was 64. RIP