As a child, you may have tried launching a toy airplane by holding it in your hand and spinning in a circle as fast as you could. This method works well enough for toys, and in the early 20th century a few engineers thought this same concept could be applied to life-sized aircraft as well.
Vox recently dug up some old patents and illustrations of a few plane-launching carousels that (thankfully) seem to have never made it off the ground. The reasoning behind the concept was that using centrifugal force to launch planes would save runway space, which would allow more airports to be built in densely populated areas. The below concept patented in 1912 shows a rather basic version of the device, and the patent below that from 1930 more closely resembles a terrifying amusement park ride than something you’d find at an airport.
While these ideas never took off, the merry-go-round concept was something aviation engineers toyed with for decades. In their July 1941 issue, Popular Mechanics even featured illustrations of one such device with an explanation of how it would function.
Then in 1951, a University of Wisconsin physicist named J.G. Winans wrote about his own success with testing the merry-go-round method. Rather than constructing an elaborate apparatus, he anchored his plane to a central point like a tether ball. He then built up speed using the plane’s own engine and took off without incident. He concluded that the mechanism would make a suitable replacement for traditional runways, though he did admit that while experiencing the force of nearly one G he “mostly found it uncomfortable.” Despite his endorsement, runways never lost their status as an airport fixture.