Vacuum Airship: A hypothetical kind of aerostat, or lighter-than-air flying machine. This one, instead of displacing air with a lighter lifting gas such as helium, has a rigid hull “filled with vacuum.” Okay, that’s a silly way of putting it. The air is pumped out while the hull retains its volume. Just in case you think the A to Z Challenge has driven me crazy and I’ve become so desperate at the tail end of the alphabet that I’ve started making stuff up, here’s a link to the Wikipedia article. Naturally, a nylon or silk envelope would simply collapse, so you need something really light and strong to make a rigid vessel out of. Titanium probably couldn’t do it. Futuristic materials such as graphene might work, but what you really want is an airtight force-field. Then you build a keel with a control cab and some propellers, and just create an air-displacing vacuum volume hull above you as you go. Big load? Crank up the volume. Between cargo-hauls? Shrink it down to a streamlined shape just big enough to support the permanent mechanical parts and fly fast to your next job. For extra points, shape the vacuum hull to generate lift: an airship that does this is called a dynastat. With force-field tech, you could alter the shape of the dynastat on the fly for optimal efficiency and as you sped up and increased aerodynamic lift, you could actually shrink the vacuum hull down a little. I want one.
Tech Level: Extremely high. Might work as Solarpunk. Best suited to Far Future or Space Opera.
Appeared In: Nothing that I know of. Illuminate me.
For Your Plot: On the plus side, it would be adjustable to fly on almost any planet with an atmosphere, so it would make a great scout ship for your intrepid team of exoplanet explorers. On the minus side, a power failure would be a downer.