Quirium Cascade Mine
Simply put, a Q-bomb (or to use its proper name, a quirium cascade mine) is a chain reaction device. It is a very small bomb, and has been described as being 'like a minature supernova, and just as deadly'. The gravitic shockwave it emits causes any matter caught within its range to be annihilated in another deadly gravitic flash, resulting in a 'domino topple' effect. This means the initial Q-bomb explosion is only the start. Secondary explosions (the strongest caused by the destruction of its victims hyperdrives) progress in much the same way, catching further objects - until there is no more significant matter to be consumed by the expanding waves of destruction.
The explosion expands in a sphere from the initial detonation. It is accompanied by the emission of high energy photons (from gamma rays to visible light, mostly in the upper end of the spectrum). The expansion of the sphere is easily observable (from a safe distance) and travels relatively slowly. The word 'relatively' is key here - most ships can't outrun the expanding sphere without witch space fuel injectors, and if a ship doesn't make good its escape early on, even injectors may not get the craft out of trouble.
The results of a Q-bombing can be extremely spectacular.
The Q-bomb is not a very effective offensive weapon. Pirates seldom carry the device as it destroys everything in its path - so it is no use for extracting cargo from a fleet of traders. Typically it is only carried by traders, and used as a last ditch defence: for many trading vessels, the use of a Q-bomb is suicide, even with the timer set to its longest launch to detonation interval.
Many commanders who have used a Q-bomb have not lived to tell the tale - even in a fast craft like a Fer de Lance, it is necessary to fly directly away from the device as soon as it is launched, otherwise the sinister blue sphere of energy will catch up and destroy the ship that launched the weapon. Most manufacturers recommend that the device is only carried on ships that have witch space fuel injectors.
The Q-bomb is carried on a standard missile mounting point. Select the Q-bomb like any other missile (T). It does not need to be fixed on any particular target (and cannot be targeted). Release it like a normal missile (M). Be sure to drop it as close to the centre of any action you wish to see an end to.