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. {the
predecessor of NASA--jbh} is America's most authoritative source of
aerodynamic knowledge. I knew they had already tried

{p. 88}

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.