Metal-clad airships are airships which have a very thin airtight metal envelope, rather than the usual fabric envelope. This shell may be either internally braced as with the designs of David Schwarz, or monocoque as in the ZMC-2. Only four ships of this type are known to have been built, and only two actually flew: Schwarz's aluminum ship of 1893 collapsed on inflation; Schwarz's second airship flew at Tempelhof, Berlin in 1897, landed but then collapsed; the ZMC-2 flew 752 flights between 1929 and scrapping in 1941; while the Slate City of Glendale, was built in 1929 but never flew.
ZMC-2
An airship or dirigible balloon is a type of aerostat or lighter-than-air aircraft that can navigate through the air under its own power. Aerostats gain their lift from a lifting gas that is less dense than the surrounding air.
A modern airship, Zeppelin NT D-LZZF in 2010
Dirigible airships compared with related aerostats, from a turn-of-the-20th-century encyclopedia
U.S. Navy airships and balloons, 1931: in the background, ZR-3, in front of it, (l to r) J-3 or 4, K-1, ZMC-2, in front of them, "Caquot" observation balloon, and in foreground free balloons used for training
The air-filled red balloon acts as a simple ballonet inside the outer balloon, which is filled with lifting gas.
