Photon Torpedoes
The photon torpedo was developed as a tactical weapon that could be used while a starship is traveling at warp - a situation in which phasers are useless.

First developed in 2215, photon torpedoes are explosive weapons which, unlike phasers, can be fired at warp speed. They are carried as standard on most Federation starships, and are often fitted to space stations such as Deep Space 9.

The photon torpedo took some time to fully develop. Casing and delivery systems were in place early in the 23rd century, but the first models had a range of just 750,000 kilometers and produced a relatively low explosive yield. A much more advanced photon torpedo now exists; this latest model has an upper range limit of 4,050,000 kilometers, as fire from a starship at warp. If launched from a stationary platform, the torpedo will never reach warp 1, and therefore cannot travel nearly as far. This range can be extended, but because the engine draws fuel from the matter-antimatter tanks, this can be done only at the expense of the torpedo's destructive power. The photon torpedo's explosive power comes from the matter and antimatter packets, which are usually delivered at warp speed by a small matter-antimatter fuel cell, then thrust together to cause an explosion. The torpedo has a lozenge-shaped casing made of molded gamma-expanded duranium and a plasma-bonded terminium outer skin. The latest casing measures 2.1 by 0.76 by 0.45 meters, an weighs 186.7 kilograms.

When used as a weapon, the torpedo contains explosive material, target acquisition, guidance, detonation assemblies, and a warp sustainer engine. Due to its small size, the warp sustainer engine is not a true warp engine, and is more accurately described as a matter-antimatter fuel cell. If the torpedo is launched at warp speed, the sustainer coils in the fuel cell acquire warp velocity from the torpedo launcher tube. The matter and antimatter are carried aboard the torpedo in tiny packets; this method increases the effective contact area by three orders of magnitude over the same amount of matter and antimatter safety measure, the packets are kept far apart within the torpedo until just after launch. The photon torpedo carries a maximum of only 1.5 kilograms of antimatter, but the use of packets yields destructive power greater than that caused by a Galaxy-class antimatter pod rupture. It is an impressive weapon in the Starfleet arsenal.