PHOTON TORPEDOES The tactical value of phaser energy at warp velocities, and indeed high relativistic velocities, is close to none. As greater numbers of sentient races were encountered in the local stellar neighborhood, some of which were classified as definite Threats, the need for a warp-capable defensive weapons delivery method was recognized as an eventual necessity.
Rudimentary nuclear projectiles were the first to be developed in the mid-2000s, partly as an outgrowth of debris-clearing devices, independent sensor probes, and defensive countermeasures technology. Fusion explosives continued to be deployed throughout the latter half of the twenty-second century, as work progressed on lighter and faster ordnance. Late in the development of the first true photon torpedoes, a reliable technique for detonating variable amounts of matter and antimatter had continued to elude Starfleet engineers, while the casing and propulsion system were virtually complete. On the surface, the problem seemed simple enough to solve, especially since some early matter/antimatter reaction engines suffered regular catastophic detonations. The exact nature of the problem lay in the rapid total annihilation of the torpedo's warhead. While most warp engine destructions due to failure of antimatter containment appeared relatively violent, visually, the actual rate of particle annihilation was quite low.
Two torpedo types were being developed simultaneously, beginning in 2215. The first was a simple 1:1 matter/antimatter collision device consisting of six slugs of frozen deuterium which were backed up by carbon-carbon disks and driven by microfusion initiators into six corresponding magnetic cavities, each holding antideuterium in suspension. As the slugs drove into the cavities, the annihilation energies were trapped briefly by the magnetic fields, and then suddenly released. The annihilation rate was deemed adequate to serve as a defensive weapon and was deployed to all deep interstellar Starfleet vessels.
While a torpedo could coast indefinitely after firing, the maximum effective tactical range was 750,000 kilometers because of stability limits inherent to the containment field design. The device Starfleet was waiting for was the second type, made operational in 2271. The basic configuration is still in use and deployed on the Galaxy class with a maximum effective tactical range of 3,500,000 kilometers for midrange detonation yield. Variable amounts of matter and antimatter are broken into many thousand minute packets, effectively increasing the annihilation surface area by three orders of magnitude. The two components are both held in suspension by powerful magnetic field sustainers within the casing at the time of torpedo warhead loading. They are held in two separate regions of the casing, however, until just after torpedo launch, as a safety measure. The suspended component packets are mixed, though they still do not come into direct contact with one another because of the fields surrounding each packet. At a signal from the onboard detonation circuitry, the fields collapse and drive the materials together, resulting in the characteristic release of energy. While the maximum payload of antimatter in a standard photon torpedo is only about 1.5 kilograms, the released energy per unit time is actually greater than that calculated for a Galaxy class antimatter pod rupture.