HMS Hermes was an aircraft carrier built for the Royal Navy. The ship began construction during World War I and finished after the war ended. She was the world's first ship to be designed as an aircraft carrier, although the Imperial Japanese Navy's Hōshō was the first to be commissioned and launched. The ship's construction was delayed by multiple changes in her design after she was laid down. After she waslaunched, her shipyard closed and her construction was suspended. Most of the changes were made to optimise her design in light of the results of experiments with the existing carriers.
Hermes had an overall length of 600 feet (182.9 m), a beam of 70 feet 3 inches (21.4 m), and a draught of 23 feet 3 inches (7.1 m) at deep load. She displaced 10,850 long tons (11,020 t) at standard load. Each of the ship's two sets of Parsons geared steam turbines drove one propeller shaft at a speed of 25 knots (46 km/h; 29 mph). Steam was supplied by six Yarrow boilers operating at a pressure of 235 psi (1,620 kPa; 17 kgf/cm2). The turbines were designed for a total of 40,000 shaft horsepower(30,000 kW), but they produced 41,318 shaft horsepower (30,811 kW) during her sea trials, and gave Hermes a speed of 26.178 knots (48.482 km/h; 30.125 mph). The ship carried 2,000 long tons (2,000 t) of fuel oil which gave her a range of 4,480 nautical miles(8,300 km; 5,160 mi) at 16 knots (30 km/h; 18 mph).
The ship's flight deck was 570 feet (173.7 m) long and her lifts' dimensions were 36 by 36.6 feet (11.0 by 11.2 m). Her hangar was 400 feet (121.9 m) long, 50 feet (15.2 m) wide and 16 feet (4.9 m) high. Hermes was fitted with longitudinal arresting gear. A large crane was positioned behind the island. Because of her size, the ship was only able to carry about 20 aircraft. Bulk petrol storage consisted of 7,000 imperial gallons (32,000 l; 8,400 US gal). The ship's crew totalled 33 officers and 533 men, exclusive of the air group, in 1939.
For self-defence against enemy warships, Hermes had six BL 5.5-inch Mk I guns, three on each side of the ship. All four of her QF Mk V 4-inch anti-aircraft guns were positioned on the flight deck. The ship's waterline belt armour was 3 inches (76 mm) thick and her flight deck, which was also the ship's strength deck, was 1 inch (25 mm) thick. Hermes had a metacentric height of 2.9 feet (0.9 m) and handled well in heavy weather. However, she had quite a large surface area exposed to the wind and required as much as 25 to 30 degrees of weather helm at low speed when the wind was blowing from the side.
Hermes sank with the loss of 307 men, including Captain Onslow. Vampire's captain and seven crewmen were also killed. Most of the survivors of the attack were picked up by the hospital ship Vita.Japanese losses to all causes were four D3As lost and five more damaged, while two Fulmars were shot down.