The US Navy’s C-7 airship was the first to successfully conduct a flight using helium as the fill gas. C-class airships were patrol airships and were an upgrade to B-class airships after World War I. They were larger, had two engines and a greater resistance. Although the initial idea was thirty, eventually only ten were built. They were delivered in 1918 and served until 1922. As they arrived at the end of the war, their use was not really military, but became an experimental airship and for training activities. The C-1 was the first to launch an aircraft in flight, the Curtiss JN-4 “Jenny” two-seater biplane, over Fort Tiden, New York. The C-5 was the most popular, as it participated in an attempt to cross the Atlantic, parallel to the NC-4 seaplane. The matter ended badly, as he suffered an accident when a storm made him lose control. Although the accompanying ship tried to restrain him by cables, eventually the captain and crew had to jump and the airship was eventually lost. More tragic luck had the C-8, which suddenly exploded on a landing at Camp Holabird, Maryland, injuring 80 civilians who enjoyed the spectacle. The C-3 burned, but in the air, on July 7, 1921.
The C-7 did not have a sad and fiery end, as it would be the one that was inflated for the first time with helium. It was flown by Ralph F. Wood from Norfolk, Virginia to Washington on December 1, 1921. A hit that was published the next day in the New York Times. It was dismantled together with the C-9 in 1922, to pass away.
Helium is a noble gas with atomic number 2 and its name honors the Greek god of the Sun, Helios. It is the first element discovered outside the Earth, as it was found by analyzing the spectrum of the solar chromosphere. During a solar eclipse, astronomer Pierre Janssen detected a yellow line 587.49 nanometers long, which turned out to be the spectrum of a new element, helium, although it was initially confused with sodium. It was on August 18, 1868, and on October 20 of the same year, the English astronomer Joseph Norman Lockyer also observed the yellow line in the solar spectrum. Lockyer was the one who came to the conclusion that it was an unknown element on earth and it would be the English chemist Eduard Frankland who would confirm the results and who would propose the name helium, given the history of the discovery.
Although helium is the second most abundant chemical element in the Universe, the reserves we have for obtaining helium are being depleted more rapidly than nature’s ability to replenish it. Being non-flammable and having a density 8% lower than hydrogen, it makes it an ideal gas for filling balloons and zeppelins. There are many applications of helium that raise the eyebrow when we see children with balloons at the fair: deep dives, gas chromatography, supersonic wind tunnels, arc welding, cooling agent in nuclear reactors, manufacture of silicon and germanium crystals , magnetic resonance imaging, etc.
It is extracted by fractional distillation from natural gas, since it contains 7% helium. It has the lowest boiling point on the periodic table, so it is used to liquefy almost any gas, especially nitrogen and methane. Although helium can be synthesized by high-speed proton bombardment onto lithium or boron, it is an economically unfeasible process.
The German airship LZ 129 Hindenburg caught fire in 1937, 16 years after helium airships had already been tested. This one did manage to make a transatlantic flight. The disaster occurred after waiting for docking, at the mooring base was Naval Air Station Lakehurst (New Jersey), after several hours due to inclement weather. The trigger was a fire from San Telmo in the stern. It is a flash produced by the corona effect discharge caused by the ionization of the air. This spark, which may seem harmless to us, caused a rapid fire that spread almost instantaneously throughout the airship. The structure fell on the passengers and they jumped from a height of 15 meters. The fire took just 32 seconds to completely destroy the LZ 129 Hindenburgse. 35 of the 97 people on board died. Hitler ordered the termination of the commercial airship fleet after the accident. In the US they continued to use them, thanks to helium.
Fat Man was the nuclear bomb that was dropped on Nagasaki, Japan, on August 9, 1945. It was the “Mark III” bomb and its ballistics had not turned out to be very good. For this reason, Los Alamos engineers rethought the design. And they were based on the C-class airships of the US Navy to create a new hull. With a flat nose of about 74 cm in diameter and a drag plate on the tail of about 84 cm in diameter. The maximum width was 1.5 m, with a length of 3 m. The result is the Mak IV, an improved Fat Man, although ultimately it is not exactly the same as a C airship.
