Explorer-class submarine
The Explorer-class submarines were two experimental Royal Navy boats built by Vickers-Armstrongs in Barrow-in-Furness to test a hydrogen peroxide (HTP) and diesel propulsion system. Based on the Porpoise-class hull and fitted with retractable streamlining gear, they had no torpedo tubes or radar—just one periscope—and backup diesel engines to recharge the batteries and surface.
The two boats, Excalibur and Explorer, were completed for about £2 million and served from 1958 to 1965. They were designed to run steam turbines underwater, with the steam produced by the reaction of HTP and diesel fuel. On the surface they used conventional diesel-electric propulsion. They could reach very high underwater speeds for the time—peaking above 30 knots (over 46 km/h), with a sustained underwater speed around 26.5 knots (about 49 km/h) for up to three hours, and about 22 km/h (12 knots) for 15 hours on a single turbine. Because of the peroxide used, they earned the nicknames Blonde class; there were also serious accidents, leading to the Exploder nickname for the class and Excalibur’s disparaging tag Excruciater.
The program proved the concept was dangerous and not reliable. The use of HTP to power torpedoes contributed to disastrous losses, including HMS Sidon and the Kursk, and when the United States developed a nuclear reactor for submarines, the HTP project was abandoned. The two boats were not converted to normal diesel submarines; Explorer was sold for scrap for £13,500, and Excalibur followed later.
In the years afterward, other countries developed air-independent propulsion, but hydrogen peroxide fell out of use, with liquid oxygen systems becoming the preferred option for such auxiliary power.
This page was last edited on 3 February 2026, at 07:48 (CET).