Launching Planes off Carriers

Some of the most valuable assets in any modern navy's fleet are its aircraft carriers. They give a nation the ability to patrol vast areas of the ocean, control the skies over its seas, and strike at the less armored decks of opposing ships. They are a symbol of naval might, but they would have been almost useless at their debut without a way to launch their planes into the air.

At the very beginning of aviation, most aircraft were incredibly light - build out of wood and canvas - and this meant that they needed very little space to take off. It was great for their use as a light and nimble reconnaissance platform, but didn't do very well when tasked to chase other planes down or take hits from a machine gun. With the introduction of larger aircraft and the use of heavier materials such as aluminum, however, this rapidly changed and larger runways had to be build in order support these more powerful machines. During WWI, the use of planes from the decks of ships was theorized but its implementation was very limited. Light canvas aircraft would take off from the ships with ease but would find landing impossible and as a result often had to crash into the sea. During this time the first aircraft catapults were also designed with the first successful catapult launch off the USS North Carolina in 1915.

A biplane takes off from a launching platform fitted to the USS Pennsylvania to return to an airfield, after the first shore-to-ship aircraft landing off San Francisco in early 1911. Hulton Archive/Getty Images

The metal planes of WWII with their longer runway requirements meant that the aircraft carriers and catapults had to advance if they were to remain competitive in the new war. In the interwar period the US had experimented with various catapult systems including compressed air ,gunpowder, and explosive charges. Most of their carriers during the war, however, used a hydraulic launching system. This was great for the purpose built carriers of the US and other large navies, but the British Royal Navy was stretched thin warding off the incessant German U-Boat attacks in the Atlantic. They even went as far as to arm some of their merchant ships with rocket powered catapults and sea hurricane fighter planes. These became known as the "Hurricats", and were incredibly dangerous to pilot. Since the rocket powered catapult had no means to safely land the plane, pilots would have to either fly back to land or bail out of the plane before crashing into the ocean and hope to be picked up by their ship. It was crude, but at a time when Britain needed more planes in the ocean than it could get, it worked well enough.

Test launch of a Hurricane using the rocket-catapult of a CAM ship, Greenock, Scotland, 31 May 1941

After the war, the UK started looking ahead to the next generation of Aircraft Carriers and how to best power their catapults. Their Commander Collin C. Mitchell suggested implementing a steam powered catapult, and after its successful development and testing on the HMS Perseus it entered service around the world in the 1950s. From then until now, this has continued to be the most popular method by which to launch planes from ships.

Perseus with two de Havilland Sea Hornets and a Short Sturgeon on deck

and the experimental steam catapult fitted during trials in the early 1950s.

Recently though, advances have been made in catapult technology. A new launch system has been developed and is being used on board the new USS Gerald R. Ford class aircraft carriers. This system is called the Electromagnetic Aircraft Launch System (EMALS for short). It uses Electromagnetic force in order to accelerate the catapult arm to speed and push the plane with incredible force. It's more smooth in its acceleration than the instantaneous acceleration provided by steam, which in turn means that EMALS does less damage to the air-frame than traditional stream powered catapults would. It also has more versatility as the power of the electromagnets can be adjusted to launch both smaller and larger aircraft than steam powered catapults can.

Gerald R. Ford Underway for Builder's Sea Trials on 8 April 2017

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