A privately developed manned rocket will attempt to reach space this month, its builders said Wednesday. It would be the first non-governmental flight to leave Earth's atmosphere.  

SpaceShipOne (search), created by aviation designer Burt Rutan and funded by billionaire Paul Allen (search), will attempt to reach an altitude of 62 miles on a suborbital flight over the Mojave Desert (search) on June 21.

The rocket plane reached an altitude of about 40 miles during a test flight May 13.

Suborbital flights are essentially up and down. The craft does not reach speeds fast enough go into orbit around the Earth.

If the attempt is successful, SpaceShipOne will compete for the Ansari X Prize, a competition in which $10 million goes to the first reusable rocket able to carry three people into space on a suborbital flight, return them safely to Earth, and repeat the feat within two weeks with the same vehicle.

A number of other private organizations are also developing contenders for the prize.

"Every time SpaceShipOne flies we demonstrate that relatively modest amounts of private funding can significantly increase the boundaries of commercial space technology," Allen, co-founder of Microsoft, and founder and chairman of Vulcan Inc., said in a statement.

The cost of SpaceShipOne has not been revealed.

SpaceShipOne is carried aloft by a specially designed jet aircraft and then is dropped into a glide at an altitude of about 50,000 feet. The pilot then fires the rocket motor and pulls up into a vertical climb.

The June attempt will involve an 80-second rocket firing that will accelerate the craft to Mach 3. It will then coast up to the target altitude before falling back to Earth. The pilot will experience weightlessness for more than three minutes. The glide back to the ground will take 15-20 minutes.