Impulse power
Impulse power was source of  used to operate a ship's impulse engines. The amount of impulse power applied to an engine's output determined the impulse speed, i.e. velocity, at which a ship would travel. () 

Impulse power was generated by increasing the deuterium injection rate, then configuring the driver coils for impulse speed, by setting EPS taps to level three. () Operational primary ODN lines were also required to initiate impulse power. ()

Impluse power was a consumable, its availability could be measured by percentage. () Other systems could be rerouted to help boost impulse power, such as the auxiliary generators. (; ; ) As well, it could be combined with warp power to allow for a "massive thrust" in the direction traveled. ()  

Impulse power could also be applied to other systems, including the deflector array, sensors, shields, and tractor emitters. (; ; )

Uses of impulse power 
The  used "impulse power two" to break free from the tractor beam used by Balok's pilot vessel. ()

After the  had been critically damaged by the planet killer encountered in 2268, and the landing party, including Captain James T. Kirk and Lieutenant Commander Montgomery Scott, became stranded on the derelict ship as his ship, the Enterprise was under attack, Kirk complained that "[w]e're stuck, blind, and deaf," to which Scott added, "And paralyzed. No power." Though Scott had previously stated the ship's warp drive was "a hopeless pile of junk", he figured he could coax some maneuvering power out of the impulse engines after Kirk suggested that Scott get him impulse power: "Half-speed, quarter-speed, anything."  

At the same time, the Enterprise, which was also damaged by the planet killer was fast enough to stay ahead of it under emergency impulse power, but doing so would exhaust their fuel supplies in less than a day. ()

When the refit Enterprise first cleared spacedock, Admiral James T. Kirk ordered Sulu to engage impulse power: "Ahead, warp 0.5." ()

In 2285,  Saavik piloted the Enterprise out of spacedock at one-quarter impulse power. Later, the , under the command of Khan Noonien Singh, approached the Enterprise at one-half impulse power, under the guise of being "friends". Then, following the initial battle between the two vessels, the Enterprise was able to "proceed at impulse power" after its auxiliary power had been restored in order proceed at "[b]est speed to Regula I." The Reliant also lost impulse power in the battle, and after Khan was lead to believe that the Enterprise had neither main nor auxiliary power, he concluded that upon the restoration of their impulse power, they were "[m]ore than a match for poor Enterprise," as the two ships orbited the planetoid. Following the Enterprises escape and run for the nearby Mutara Nebula, Admiral Kirk taunted Khan, who responded by issuing "[f]ull impulse power!" to enhance his pursuit. ()

During the pursuit of Jarok's scout ship by a Romulan warbird, a review found that as a result of the scout sustaining engine damage, it was forced to slow to 0.615 impulse power. ()

After the  struck the first time by a quantum filament, in 2367, it lost both warp and impulse engines. Following a second strike, the ship lost the ship's computer but still had impulse power, "but not much else." After the engineering station was brought back online, a more specific analysis was made, and it was determined that the ship had "half impulse power available." () 

Physics