Torpedo's are self propelled projectiles fired from atmospheric vehicles and space ships. They contain a warhead, fuel source (unspent fuel adds to the destructive force when impact occurs), and guidance thrusters. Forward momentum for Torpedoes comes primarily from the launcher. The inertia from the vehicle launching the torpedo combined with the additional thrust put behind the torpedo by the launcher equals the max speed the torpedo. The guidance thrusters on the torpedo are mearly to guide it to its target. If the torpedo misses its target, it will detonate at the closest point it can reach.
Some torpedoes can be equipped with multiple warheads that will spread out over its target. In order to accomplish that feat and not take up more space, means that the warheads are much less powerful than a torpedo with a concentrated warhead.
Mines are torpedoes that are designed to be left in place... they are not fired, but laid. They contain a warhead, period. Some mines are also equipped with guidance thrusters and fuel so that they can adjust their position in case they drift, or in order to move closer to an approaching ship. It is also possible to equip a mines with self replication hardware to replace any mines that may have been lost.
Due to their stationary nature it is possible to install multiple full size warheads onto mines, including special warheads that have been hollowed out for the emplacement of a cloaking device to hide the mine from view.
Missiles are much larger than torpedoes and include their own propulsion systems strong enough to leave a planets gravity field. They are constructed with a warhead section (this warhead section could be installed with a small space craft, or more than one warhead at a time), four times the fuel space of a torpedo, guidance thrusters, and a primary propulsion device of virtually any type.
Explosive warheads include chemical and fragmentary explosives, not dissimilar to what is used today.
Traditional nuclear warheads. Usually not used because the resulting explosion radiates the area, making it unlivable for many years to come. Any people not killed in the initial explosion does will usually die slowly of radiation poisoning.
Used in B5
When antimatter comes into contact with matter, the result is highly explosive. An electromagnetic field or some other form of force field can contain antimatter. When an antimatter warhead detonates it simply turns off the containment field, releasing the antimatter to mix with and detonate all the matter nearby.
Used in Star Trek
Gravity warheads are possible only after the development of artificial gravity. They detonate with an intense burst of gravity, acting as a temporary black hole, to destroy and crush anything nearby.
Used in B5
Plasma warheads explode and envelop their target in a ball of destructive plasma.
used in Star Trek.
This type of warheads are designed to release either a biological agent or a toxic gas into the nearby area. This type of a warhead is only useable in an atmosphere against ground troops. Nanites may also be released. A nanite filled warhead can be effective in space as well, working against ships as well as personnel.
Used in ST:Voyager with nanites
Some warheads have energy weapons mounted in them. The warhead only needs to come near the target, for it to fire its energy weapon into the target.
used in Honor Harrington books
ECM warheads emit strong electrical interference designed to disrupt the electrical and scanning systems of any nearby ships.
used in BSG
This type of "Warhead" is useful only on mines. It emits a massive flash of light designed to blind pilots. While ECM mines make it impossible to fly using instruments, Flash Mines make it impossible to fly without them by depriving the pilot from looking out of his craft.
used in BSG
This warhead is responsible for controling and guiding other mines or missiles, to assist hitting their targets.
Used in SB/Yamato