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USS X-1's hull under construction, unknown date. Fairchild Archives via Warbird Information Exchange.org

USS X-1's control room, date unkown. Fairchild Archives via Warbird Information Exchange.org

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Arguably the main distinction between USS X-1 and its Royal Navy counterparts relates to its engine. Unlike the standard diesel engines of the X class and XE class, USS X-1 featured a more advanced, closed-cycle hydrogen peroxide diesel engine, similar in principle to the engine on the German Type-XVII coastal submarine. When submerged, USS X-1’s engine relied on the catalytic decomposition of the hydrogen peroxide to generate oxygen (on the surface, a small air inlet was used to operate the engine).

The hydrogen peroxide – a colorless liquid that is often used as a bleaching agent in high quantities and can cause irritation to the eyes, nose, skin, and throat if ingested – was transported onto the vessel in rubber bags, surrounded by seawater. In using hydrogen peroxide, it was envisaged that USS X-1 would be able to travel at faster speeds without the need to resurface.

When the vessel was placed into service in October 1955, it began work in a research capacity in order to test the Navy’s ability to defend harbors against small, adversary submarines. The vessel was also designed for more offensive purposes – principally, as a means of attacking enemy ships using its side-mounted charges which, according to Sutton, would be dropped below the target vessel.

USS X-1 in Long Island Sound, 1955. U.S. Naval Institute via Naval History and Heritage Command