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SS (Submarine Scout or Sea Scout) class airships were simple, cheap and easily assembled small non-rigid airships or "blimps" that were developed as a matter of some urgency to counter the German U-boat threat to British shipping during World War I. A secondary purpose was to detect and destroy mines. The class proved to be versatile and effective, with a total of 158 being built in several versions.
Soon after the outbreak of World War I, the threat to British shipping from German submarines became increasingly apparent, with numerous losses occurring during October and November 1914. Then, on 4 February 1915, a communiqué issued by the Imperial German Admiralty declared that: "All the waters surrounding Great Britain and Ireland, are hereby declared to be a war zone. From 18 February onwards every enemy merchant vessel found within this war zone will be destroyed."
The situation had become critical and the Admiralty recognised that airships would be effective at spotting submarines and useful for Fleet observations, but at that time Britain's airship fleet consisted of just seven craft - four RNAS airships (HMA 17, 18, 19, and 20), two continental ships and a small Willows training craft - with only four airfields existing that possessed hangars capable of housing them. Consequently, on 28 February the First Sea Lord, Admiral Lord Fisher, called a meeting with Commander E. A. D. Masterman (Officer Commanding the Naval Airship Section) and representatives from Vickers and the London-based firm of Airships Limited to discuss the possibilities of creating a fleet of suitable patrol airships, sometimes referred to as "scouts".
The type was to have a speed of 40-50 mph (64-80 km/h), carry a crew of two, 160 lb (73 kg) of bombs, wireless equipment, fuel for eight hours flying, and capable of reaching an altitude of 5,000 ft (1,500 m). Most importantly the design had to be simple, in order to ease production and to facilitate training of the crews, since the new airships, designated the "Submarine Scout" or "Sea Scout" (SS) class, needed to be operational within weeks rather than months.
Prototype
The prototype SS craft was created at RNAS Kingsnorth on the Hoo Peninsula,[6] and was effectively a B.E.2c aeroplane fuselage and engine minus wings, tailfin and elevators, slung below the disused envelope from airship HMA No. 2 (Willows No. 4) that had been lying deflated at the Royal Aircraft Establishment (RAE), Farnborough Airfield. It was ready for evaluation trials within a fortnight of approval being granted for the scheme, and on 18 March 1915 the first SS class airship entered service. The whole process had taken less than three weeks, and voicing his approval, Admiral Fisher made the famous comment: "Now I must have forty!"
The officer commanding the Kingsnorth facility was Wing-Commander N. F. Usborne, who also assisted in the design of the airship. In recognition of his contributions the following comment was made: "Admiral Sueter desires to place on record his high appreciation of the hard work and devotion to the airship cause displayed by Commander Usborne. Far into the night and the early hours of the morning this scientific officer worked to make these airships a success and due to him in large part their wonderful success was due."
Two private firms, Armstrong Whitworth and Airships Ltd., were also invited to submit designs and consequently three versions of the SS class blimp were produced: the SS "B.E.2c", the SS "Armstrong Whitworth" and the SS "Maurice Farman" (thus named because the car designed by Airships Ltd. resembled a Farman aeroplane body).
Envelope
The envelope of the experimental prototype had a volume of 20,500 cu ft (580 m3) of hydrogen gas, but production models used a 60,000 cu ft (1,700 m3) envelope of similar shape that provided a typical gross lift of 4,180 lb (1,900 kg),[8] a net lift of 1,434 lb (650 kg) and a disposable lift of 659 lb (299 kg) with full fuel tanks and a crew of two on board. Each of the SS versions used similar envelopes that were composed of four layers: two of rubber-proofed fabric with a layer of rubber between them, and a further rubber layer on the inner, or gas surface. The external surface had five coats of dope applied to it to protect it from the elements and to render the envelope completely gastight. The first two coats were of "Delta dope" (a flexible dope used for the first time in 1913 on the British Army semi-rigid airship Delta[10]), followed by two of aluminium dope and finally one of aluminium varnish. To stiffen the nose of the envelope and to prevent it blowing in, 24 canes were arranged radially from its centre and covered with an aluminium cap.