While the speeds of airplanes and cars have made significant advancements, the speed of warships, particularly aircraft carriers, seems to have “stagnated” at around 30 knots (equivalent to 55.56 km/h). What has created this “barrier”?
In 1903, the Wright brothers invented the airplane, and just 44 years later, the first aircraft surpassed the speed of sound. Similarly, the automobile was invented in 1885, and just 14 years later, its speed exceeded 100 km/h. However, for more than 100 years, the speed of warships, especially aircraft carriers, has remained at approximately 30 knots. So, what has limited the speed development of warships, and what does the unit “knot” mean in maritime terms?
The primary reason limiting the speed of warships is water resistance.
The unit “knot” originates from the 16th century. At that time, sailors calculated the speed of ships by dropping a rope with evenly spaced knots into the sea. By counting the number of knots pulled out in a fixed time period, they could determine the ship’s speed. One “knot” is equivalent to 1 nautical mile per hour, and 1 nautical mile equals 1,852 meters, or approximately 1.852 km/h. This unit is widely used in maritime contexts because it corresponds with maps and positioning systems that use latitude and longitude.
Aircraft carriers, with speeds of around 30 knots, equivalent to 55.56 km/h, are slower than personal cars. The main reason limiting the speed of warships is water resistance. When an object moves through water, the resistance is significantly greater than when moving through air. For example, a bullet shot into water loses its kinetic energy after just 1 meter. This illustrates the challenges of increasing ship speeds due to the need to overcome substantial water resistance.
Moreover, the weight of warships, often exceeding 10,000 tons, along with powerful propulsion systems, is also a limiting factor. Increasing engine power to boost speed requires larger and heavier engines, which complicates design and space on the ship. For instance, the United States’ Lexington-class aircraft carrier in World War II had a displacement of 43,000 tons and an engine of 180,000 horsepower, yet its maximum speed was only 33 knots. The Iowa-class battleship, despite having a more powerful engine (210,000 horsepower), also only reached similar speeds due to energy efficiency limitations.
To increase speed from 30 to 50 knots, engine power would need to increase sevenfold, but the current propulsion system lacks the capability to support this. Additionally, higher speeds mean greater fuel consumption, reducing operational efficiency and range. Therefore, modern aircraft carriers like the U.S. Nimitz-class, while capable of higher speeds, typically maintain around 30 knots to ensure efficiency and economy.
Finally, modern combat models have changed, focusing not on speed but on the integration of radar technology, anti-ship weaponry, and defensive capabilities. This explains why speed is no longer a decisive factor in the design of modern warships, and warships still maintain an average speed of about 30 knots. However, with advancements in technology, it is possible that the speed of warships will improve in the future.
