The SST (Sea Scout Twin) class of non-rigid airship or "blimp" was developed in Great Britain during World War I from the earlier SS class airship. The main role of these craft was to escort convoys and scout or search for German U-boats. A secondary purpose was to detect and destroy mines. Experiments involving SSTs were carried out at the end of the war; one notable example being SSE.3 (SS Experimental) that had an envelope design known as shape "U.271", the shape from which the hulls of both R100 and R101 were derived.