The SpaceShipOne prototype will be launched from California's Mojave desert. During a May 13 flight, it was the first private rocket ship to reach the record altitude of 65 kilometers (40 miles).

SpaceShipOne was designed by Burt Rutan, whose aim is to develop a rocket that can take tourists into space, and backed by Microsoft co-founder Paul Allen. The company hopes to offer a round-trip space tour for about 100,000 dollars by about 2020.

The rocket ship has carried out three test flights. On December 17, it breached the sound barrier. It made a second flight on April 8. And on May 13, pilot Mike Melvill piloted the craft to the record altitude for a private vessel.

The pilot for the daring June 21 flight has not yet been named, but if the quest is successful, he or she will become the first astronaut to taste the magic of space in a private craft.

The vessel has two passenger seats aside from the pilot's seat, but only a pilot will be onboard during the bid to reach space.

"This flight is one of the most exciting and challenging activities taking place in the fields of aviation and aerospace today," Allen, a billionaire, said in a statement.

"Every time SpaceShipOne flies we demonstrate that relatively modest amounts of private funding can significantly increase the boundaries of commercial space technology," he said.

SpaceShipOne will be attached to a transportation plane "White Knight" that will climb to an altitude of 50,000 feet (15,240 meters) before it is set free.

The craft's pilot will then start its motor aiming to strike a speed of Mach 3 -- three times the speed of sound -- on its vertical flight into space.

As the craft enters space, its pilot will experience weightlessness for several minutes, during which it will be possible to observe the black immensity of space and the blue hue of the earth's atmosphere on the horizon.

The pilot will then adjust SpaceShipOne's wings and rudder in order to reenter the earth's atmosphere after which he or she will seek to land the craft back at the takeoff strip in the Mojave desert.

"Since Yuri Gagarin and Al Shepard's epic flights in 1961, all space missions have been flown only under large, expensive government efforts," Rutan said.

"By contrast, our program involves a few, dedicated individuals who are focused entirely on making spaceflight affordable.

"Without the entrepreneur approach, space access would continue to be out of reach for ordinary citizens. The SpaceShipOne flights will change all that and encourage others to usher in a new, low-cost era in space travel," Rutan added.

SPACE.WIRE