prototype. Slate All-Metal Airship The 1929 Slate All-Metal Airship, built in Glendale, California, had a hull constructed from corrugated aluminum panels, along with a revolutionary propulsions system consisting of a "blower" at the nose of the airship which would propel the vehicle forward by creating a partial vacuum ahead of the vessel. The centrifugal propulsion was later replaced by a conventional engine and propeller mounted on the tail end of the airship's gondola. The rolled seams intended to hold the panels together subsequently unrolled owing to gas pressure created by superheating during an attempted launch of the airship. ZMC-2 The U.S. Navy's ZMC-2 was one of the few airships to be constructed in the late 1920s. Like the Schwarz airship of the 1890s, the ZMC-2 had a system of framework integrated with stressed-skin construction that presaged both the pressurized fuselage construction used decades later in commercial airliners, and even elements of American lunar rockets, such as the Saturn V launch vehicle. The ZMC-2 was successful both in performance and longevity. Its manufacture required the development of a riveting machine and final assembly that are comparable to later rockets and transport aircraft fuselages, while being capable of dealing with aluminum skin thicknesses thin enough to allow aerostatic lift. The final assembly of the single closing seam of the two hull-halves took over two months. Filling the rigid shell was similarly problematic, requiring an expensive and time-consuming process of filling it first with carbon dioxide, then with helium, and finally purifying the helium by scrubbing residual carbon dioxide from the helium. In addition, the hull had to be strengthened to sustain the weight of the carbon dioxide during the filling process. LZ-132 In the early 1950s, Luftschiffbau-Zeppelin GmbH commissioned a design study to explore the construction of the LZ-132. The project was abandoned. American Skyship Industries Between 1982 and 1995, American Skyship Industries, a subsidiary of Wren Skyships Ltd. of the Isle of Man in Great Britain and itself a spinoff from Airship Industries, promoted its metal-clad airship projects in the USA, receiving substantial state loans but never delivering a product. Varialift Airships An aerostatic design from the company Varialift Airships PLC in the UK has designed an aluminium monocoque outer structure and internal skeleton, together with a patented buoyancy mechanism that it claims can allow it to operate at high altitudes and therefore fly faster than current designs, at lower fuel