dirigibles. But there was no propelled aircraft until 1903. {p. 109}
Either all those early sightings were wrong, or some kind of fast
aerial machine has been flying periodically over the earth for at
least two centuries.

I told him I was pretty well convinced, but that True faced a problem.
There was some conflicting evidence, and part of it seemed linked with
guided missiles. I felt sure we could prove the space-travel answer,
but we had to stay clear of discussing any weapons that were still a
secret.

"I can't believe that guided missiles are the answer to the Godman
Field saucer and the Chiles-Whitted case, or this business at Fargo.
But we're got to be absolutely sure before we print anything."

"Well, let's analyze it," said Redell. "Let's see if all the saucers
could be explained as something launched from the earth."

He reached for a pad and a pencil.

"First, let's take your rotating disk. That would be a lot simpler to
build than the stationary disk with variable jet nozzles. With a disk
rotated at high speed you get a tremendous lift, whether it's slotted
or cambered, as long as there's enough air to work on."

"The helicopter principle," I said.

Redell nodded. "The most practical propulsion would be with two or
more jets out on the rim, to spin your rotating section. But to get up
enough speed for the jets to be efficient, you'd have to whirl the