EXPLORATIONS -- a program in Special English by the Voice of America.

Today, Doug Johnson and Frank Oliver tell about the first airplane that flew out of the Earth's atmosphere. It was designed to test equipment and conditions for future space flights. The plane was called the X-Fifteen.

The pilot of the huge B-Fifty-two bomber plane pushes a button. From under the plane's right wing, the black sharp-nosed X-Fifteen drops free. It is eleven-and-one-half kilometers above the Earth.

Pilot Scott Crossfield is in the X-Fifteen's only seat. When he is clear of the B-Fifty-two, he starts the X-Fifteen's rocket engine. And so begins the first powered flight of the experimental plane designed to take man to the edge of space.

The X-Fifteen flies high over the sandy wasteland of California's Mojave Desert. Up, up it flies. After three minutes, its fuel has burned up. It is flying about two thousand kilometers an hour.

Scott Crossfield's voice tightens. His breathing [bad word] harder as the plane pushes against the atmosphere. At that speed, the pressure is three times the force of gravity.

Then the X-Fifteen pushes over the top of its flight path. It settles into a long, powerless slide toward the landing field at Edwards Air Force Base.

Designers of the X-Fifteen have warned Crossfield about the landing. They say it will be like driving a race car toward a brick wall at one hundred sixty kilometers an hour, hitting the brakes, and stopping less than a meter from the wall. Crossfield lands the plane without any problem. His success shows, as one newspaper reports, that "The United States has men to match its rockets. "

That first flight of the X-Fifteen took place in September, nineteen fifty-nine. But the story began in the Nineteen forties with the 'X' series of experimental aircraft.

The first plane ever to fly faster than the speed of sound was the X-One in nineteen forty-seven. United States government agencies and America's airplane industry realized then that it was possible to build an even faster plane. It would reach hypersonic speeds -- five times the speed of sound.

The first proposal for this new research vehicle, the X-Fifteen, was made in nineteen fifty-four. The space agency, Air Force and Navy jointly supported the program. They wanted a plane that could test conditions for future flights into space.

The project moved quickly. The North American [bad word] won [bad word] to design and build the plane. The design would be part aircraft and part spacecraft. [bad word] took less than four years to produce three X-Fifteens.

The planes were not big. They were just fifteen meters long with wings less than seven meters across. They were designed to fly at speeds up to six thousand four hundred kilometers an hour. They were designed to reach heights of eighty kilometers. Their purpose was to explore some of the problems of manned flight, during short periods, in lower space. No one had ever done that before.

The X-Fifteen project had four major goals.

It would test flight conditions at the edge of Earth's atmosphere. It would leave the atmosphere briefly, then return, testing the effects of the extreme heat of re-entry. It would provide information on the controls needed in the near weightless environment of lower space. And it would answer a very important question: How would humans react to space flight?

The X-Fifteen was a new idea. And it was built with new methods. It was covered in a new material called "inconel x." The material was a mixture of the metals nickel and chromium. It would protect the plane from high temperatures.

There were new designs for the plane's rocket engine, landing equipment and the small rockets needed to move it in space. There was a new system of liquid nitrogen to keep the pilot cool and to resist the [bad word] force of gravity at high speeds. And there was a new fuel, a mixture of liquid ammonia and liquid