Aerodynamics: Anatomy of Speed

Few airplanes now flying have provoked such far-out speculation as Lockheed's long-secret All. Since President Johnson gave the plane a sort of partial unveiling, it has been called "quasi-ballistic" and "suborbital"; it has been classed just below a Mercury capsule. Dopesters have fitted it with a rocket engine to boost it out of the atmosphere like the X-15 research plane.

Many of the far-out theories seem far from fact, but the All is nevertheless an extraordinary airplane, a technical generation ahead of any of its competitors. Lockheed's famed designer Clarence L. ("Kelly") Johnson started building the ship in 1959 as a successor to the U-2 high-altitude reconnaissance plane. Though it was the altitude champ of its day, the U-2 flew so slowly (500 m.p.h. at 70,000 ft.) that the Russians were eventually able to shoot one down. The All was specifically designed to fly high enough and fast enough to avoid trouble.

According to the authoritative magazine Aviation Week, the All was trucked in pieces out of Lockheed's secret "Skonk Works" at Burbank, Calif., and assembled for flight testing at a hidden Nevada base called "The Ranch." When its secret could no longer be kept, the airplane was described misleadingly as an "interceptor." It is more likely to be anything but. It sacrifices everything for extreme speed at extreme altitude (probably above 125,000 ft.), where there is nothing to intercept.

Speed & Thrust. Most authorities credit the All's performance to its lightness, its radical double-delta wing and its equally radical engines. The weight depends largely on lavish use of titanium, which is not much heavier than aluminum, but stands the searing heat of Mach3 flight. Titanium alloys sell for more than $5 per Ib. and are difficult to fabricate, but advanced airplanes are no respecters of cost.

The All's double-delta wing is a shrewd solution to the difficult problem of sustaining flight at three times the speed of sound while still providing good control for reasonably slow-speed loitering and landing. The broad, rear delta develops high lift at moderate speeds, but as a swept-wing plane moves faster, its center of lift shifts rearward towards the tail. If it is not counteracted in some way, this shift will make the plane dangerously nose heavy. A pilot might use his elevators to hold the nose up, but this maneuver would cause costly drag. The All licks the problem in a simple and straightforward manner; it has small lifting structures ahead of the main delta. They give almost no lift at low speed, but as speed picks up, their lift increases greatly and supports the nose. Much of the high-speed lift comes from narrow fairings that run along both sides of the long, slim fuselage and also serve to stiffen it. Aviation Week says that the space between the engine nacelles is mostly filled with a thick, winglike structure to store fuel.