Next day, I dug out my copy of Boal’s interview with D———, the famous aircraft designer. “Certainly the flying saucers are possible,” the designer had told Boal. “Give me enough money and I’ll build you one. It might have to be a model because the fuel would be a problem. If the saucers that have been seen came from other worlds, which isn’t at all Buck Rogerish, they may be powered with atomic energy or by the energy that produces cosmic rays—which is many times more powerful—or by some other fuel or natural force that our research hasn’t yet discovered. But the circular airfoil is quite feasible. “It wouldn’t have the stability of the conventional airplane, but it would have enormous maneuverability—it could rise vertically, hover, descend vertically, and fly at extremely high speed, with the proper power. Don’t take my word for it. Check with other engineers.” Before looking up a private engineer I had in mind, I went to the National Advisory Committee for Aeronautics. The N.A.C.A. is America’s most authoritative source of aerodynamic knowledge. I knew they had already tried out disk-shaped airfoils, and I asked about this first. I found that two official N.A.C.A. reports, Technical Note 539 and Report 431, discuss tests on circular and elliptical Clark Y airfoils. Both reports state that these designs were found practical. Later, I talked with one of the top engineers in the N.A.C.A. Without showing him D———’s sketch, I asked how a disk might operate. “It could be built with variable-direction jet or rocket nozzles,” be said. “The nozzles would be placed around the rim, and by changing their direction the disk could be made to rise and descend vertically. It could hover, fly straight ahead, and make sharp turns. “Its direction and velocity would be governed by the number of nozzles operating, the power applied, and the angle at which they were tilted. They could be pointed toward the ground, rearward, in a lateral direction, or in various combinations. “A disk flying level, straight ahead, could be turned swiftly to right or left by shifting the angles of the nozzles or cutting off power from part of the group. This method of control would operate in the earth’s atmosphere and also, using rocket power, in free space, where conventional controls would be useless.” The method he had described was not the one which D——— had outlined. “What about a rotating disk?” I asked the N.A.C.A. man. “Suppose you had one with a stationary center, and a large circular section rotating around it? The rotating part would have a camber built into it, or it would have slotted vanes.” He gave me a curious look, “Where’d you get that idea about the camber?” I told him it had come to me from _True_. “It could be done,” he said. “The slotted-vanes method has already been tried. There’s an engineer in Glendale, California, who’s built a model. His name’s E. W. Kay.”