The idea that an airplane can fly endlessly carrying heavy loads of passengers and cargo without burning any fuel, can stop and hover in place weightless at any time, and can takeoff and land vertically is a radical departure from accepted thought concerning aviation.
Harnessing gravity may be more technically described as the science of harnessing mass differentials.
If you visit your local Elementary School’s library (if it’s old enough), you may be able to find a copy of “Tom Swift and the Repelatron Skyway,” credited to “Victor Appleton II,” though that’s likely as fictitious as anything in the books.
A subplot of the story is the young inventor’s “Para-plane,” part airplane, part blimp. One day, the motor conked out, and he was forced to navigate pretty much as described on the site (though at lower altitudes).
Far from a new idea, though the temperature-at-altitude for condensing the gas to a fluid (probably barely-bouyant Methane), is a new wrinkle.
The gas clearly cannot be hydrogen or helium, which are the best lifting gases (they require colder temperatures to liquefy), so the envelopes would have to be enormous.
This might be filed under “cool, but probably impractical.”
Try this one for outlandish-but-maybe-possible:
http://www.skywindpower.com/ww/index.htm
The site’s a snore, but take a look at some of his research. This is like maybe my second visit here, so for all I know, you’ve already posted an item about this.
…or maybe it was “Tom Swift and the Electronic Retroscope” (hard to keep them straight after all these years…
Thanks Jackson,
I found Tom Swift Paraplane info here:
http://www.tomswift.info/homepage/retscope.html