Flank speed
Encyclopedia
Flank speed is a nautical term referring to a ship
's true maximum speed, beyond the speed that can be reached by traveling at full speed. Usually, flank speed is reserved for situations in which a ship finds itself in imminent danger, such as coming under attack by aircraft. Flank speed is very fuel-inefficient and often unsustainable because of engine overheating issues.
For example, the most economic speed of the Littoral combat ship
is 20 knots (10.9 m/s) providing a range of 4300 nautical miles (7,963.6 km), and endurance of 215 hours. This ship has a flank speed of 50 knots (27.2 m/s) but can only travel 1500 nautical miles (2,778 km) at flank speed, exhausting its fuel in 30 hours. Thus, its "flank speed" consumes fuel over seven times faster than most economic.
Other speeds include one-third, two-thirds, standard, and full. One-third and two-thirds are the respective fractions of standard speed. Full is greater than standard, but not as great as flank. Emergency may not be any faster than flank, but indicates the ship should be brought up to maximum speed in the shortest possible time.
In surface ship nuclear marine propulsion
, the differentiation between full speed and flank speed is of lesser significance, because these machines can be run at or very near their true maximum speed for virtually unlimited periods of time. In US Nuclear Submarine propulsion, full speed is 50% reactor power. Flank speed is 100% power, although depending upon the specifics of the individual propulsion plant, limits for the propulsion turbine first stage pressure, or limits for reactor thermal power (in MW) may be reached before 100% reactor power is reached. In addition, for flank speed, the reactor's main coolant pumps must also be shifted into fast speed.
Ship
Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...
's true maximum speed, beyond the speed that can be reached by traveling at full speed. Usually, flank speed is reserved for situations in which a ship finds itself in imminent danger, such as coming under attack by aircraft. Flank speed is very fuel-inefficient and often unsustainable because of engine overheating issues.
For example, the most economic speed of the Littoral combat ship
Littoral combat ship
A Littoral Combat Ship is a type of relatively small surface vessel intended for operations in the littoral zone . It is "envisioned to be a networked, agile, stealthy surface combatant capable of defeating anti-access and asymmetric threats in the littorals." Two ship classes are the first...
is 20 knots (10.9 m/s) providing a range of 4300 nautical miles (7,963.6 km), and endurance of 215 hours. This ship has a flank speed of 50 knots (27.2 m/s) but can only travel 1500 nautical miles (2,778 km) at flank speed, exhausting its fuel in 30 hours. Thus, its "flank speed" consumes fuel over seven times faster than most economic.
Other speeds include one-third, two-thirds, standard, and full. One-third and two-thirds are the respective fractions of standard speed. Full is greater than standard, but not as great as flank. Emergency may not be any faster than flank, but indicates the ship should be brought up to maximum speed in the shortest possible time.
In surface ship nuclear marine propulsion
Nuclear marine propulsion
Nuclear marine propulsion is propulsion of a ship by a nuclear reactor. Naval nuclear propulsion is propulsion that specifically refers to naval warships...
, the differentiation between full speed and flank speed is of lesser significance, because these machines can be run at or very near their true maximum speed for virtually unlimited periods of time. In US Nuclear Submarine propulsion, full speed is 50% reactor power. Flank speed is 100% power, although depending upon the specifics of the individual propulsion plant, limits for the propulsion turbine first stage pressure, or limits for reactor thermal power (in MW) may be reached before 100% reactor power is reached. In addition, for flank speed, the reactor's main coolant pumps must also be shifted into fast speed.