British invention of the angled flight deck by Capt D.R.F. Campbell RN in conjunction with Lewis Boddington of the Royal Aircraft Establishment at Farnborough. The runway was canted at an angle of a few degrees from the longitudinal axis of the ship. If an aircraft missed the arrestor cables (referred to as a "bolter"), the pilot only needed to increase engine power to maximum to get airborne again, and would not hit the parked aircraft because the angled deck pointed out over the sea. The angled flight deck was first tested on , by painting angled deck markings onto the centerline flight deck for touch and go landings. The modern steam-powered catapult, powered by steam from a ship's boilers or reactors, was invented by Commander C.C. Mitchell of the Royal Naval Reserve. It was widely adopted following trials on between 1950 and 1952 which showed it to be more powerful and reliable than the hydraulic catapults which had been introduced in the 1940s. The first Optical Landing System, the Mirror Landing Aid was invented by Lieutenant Commander H. C. N. Goodhart RN. The first trials of a mirror landing sight were conducted on HMS Illustrious in 1952. The US Navy built the first aircraft carrier to be powered by nuclear reactors. was powered by eight nuclear reactors and was the second surface warship (after ) to be powered in this way. The post-war years also saw the development of the helicopter, with a variety of useful roles and mission capability aboard aircraft carriers and other naval ships. In the late 1950s and early 1960s, the United Kingdom and the United States converted some older carriers into Commando Carriers or Landing Platform Helicopters (LPH); seagoing helicopter airfields like . To mitigate the expensive connotations of the term "aircraft carrier", the carriers were originally designated as "through deck cruisers" and were initially to operate as helicopter-only craft escort carriers. The arrival of the Sea Harrier VTOL/STOVL fast jet meant that the Invincible-class could carry fixed-wing aircraft, despite their short flight decks. The British also introduced the ski-jump ramp as an alternative to contemporary catapult systems. As the Royal Navy retired or sold the last of its World War II-era carriers, they were replaced with smaller ships designed to operate helicopters and the V/STOVL Sea Harrier jet. The ski-jump gave the Harriers an enhanced STOVL capability, allowing them to take off with heavier