Red-Hot X-15

There are two phases of man's navigation of space: the going out and the coming back. The Air Force's Pioneer demonstrated that the day is near at hand when a missile will soar out into free space. Last week North American Aviation, Inc. rolled out its X-15 -- a stub-winged, hard-shelled rocket.plane designed to study the other end of the problem: how to get a man back safely from outer space.

With its soft. length and 22-ft. wingspan, the X-15 looks more like a missile than an airplane. A sophisticated descendant of the X-1 rocket plane in which Test Pilot "Chuck" Yeager first broke the sound barrier (TIME, June 21, 1948), it is expected to reach 3,600 m.p.h.--twice the speed of a high-powered rifle bullet. Since such speeds cannot be maintained in the lower atmosphere, the X-15 will be carried to 35,000 ft. by a B-52, will then climb to an altitude of 100 miles. Burning liquid ammonia and liquid oxygen, its motor will develop 50,000 Ibs. of static thrust, and more power (500,000 h.p.) at full speed than the carrier Forrestal (260,000 h.p.).

Steam Steering. Operation at such dizzy height and speed has posed special problems and produced oddities in design. X-15's large vertical stabilizers are wedge-shaped, as if their trailing portions had been cut off with a saw. Wind-tunnel tests have shown that such a wedge is more efficient than a conventional streamlined shape for keeping the X-15 aligned on course as the atmosphere thins out at high altitude.

Since the air is too thin 100 miles up for any aerodynamic controls to be effective, the X-15 has an independent system of ballistic controls that need no air. In the nose are four pairs of small jets pointing up, down, left and right (see diagram). When the pilot wants to depress the nose of his craft in near-airless space, he will shoot superheated steam (produced by catalyzed hydrogen peroxide) through the upward-pointing jets. The reaction will push the nose downward. Similar jets in the wingtips will keep the wings level or make the ship bank or roll.

Instead of the usual single control stick, the X-15 has three. One is designed to resist the multiplied weight of the pilot's hand or body when he is subjected to his plane's acceleration under the push of its rocket motor because of heavy G-load or because of its deceleration on slamming down into the atmosphere. But when the X-15 is on a ballistic trajectory above the atmosphere, with its engine cut off, the pilot will be weightless. He will then shift to a second stick that will give him better control in space--presumably by directional use of the steam jets. When he gets back to the lower atmosphere and conventional speeds, he will use the third stick, which operates in the conventional way.

Glowing Wings. But soaring 100 miles above the earth is only a first step. Greater peril comes when the pilot starts down through the atmosphere to land. To offset the ferocious heat generated by the air's friction, the X-15's skin is made of Inconel X, a heat-resisting alloy that keeps its shape at a brightly glowing 1,350DEG F., when aluminum and ordinary steel have long since softened. Liquid nitrogen, which will not support combustion, is used as a coolant for both pilot and equipment, and is also vaporized to maintain pressure in the plane's interior. The pilot, who cannot breathe pure nitrogen, will have a private oxygen atmosphere inside his space suit.

As the X-15 drops back into the atmosphere, the pilot must match his speed to the density of the air. As the air grows thicker at lower altitudes, he must slow down to keep the heat of friction from softening his wings. If he comes too close to the danger point, he will veer upward into thinner air to let his plane cool off. Slowed down and cooled off, the X-15 can then glide to the ground, landing on a pair of nosewheels and two skids near the tail.

At Edwards A.F.B. on the Mojave Desert, the X-15 will be introduced to air and space by easy stages. First it will probably be dropped unpowered to see how it lands. During February 1959 North American's Test Pilot Scott Crossfield will make the first powered flights, using low-powered rocket engines. Then will come tryout flights with the 50,000-lb. engine. At some point in this feeling-out process, the X-15 will be turned over to the Air Force. Then Captain Robert A. White, 34, who became the Air Force's choice as test pilot when his friend Captain Iven Kincheloe Jr. was killed in an F-104 this summer, is scheduled to do the first "maximum-performance" testing. Translated from officialese, this means that, if all goes well, Captain White will be the first man to take the X-15 into empty space, and to bring it back, its stubby wings glowing red-hot, safely to earth.

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