The Series-5 Long-range tactical armour unit is a weapon of mass destruction that appears in the Star Trek: Voyager episode "Warhead". Created by a race called the Druoda, this interstellar missile is guided by a sentient artificial intelligence for optimum effectiveness. The device is small - only a metre long - and light enough to be carried by human hands, yet is comprised of sophisticated systems that by Starfleet standards could not normally be packed into a mechanism of its size. It is capable of travelling at warp speeds with a maximum range of 80 light years and its AI allows it to navigate its way through various space hazards such as ion storms or even a fleet of hostile ships in order to find its assigned target.
In the year 2376, the Druoda had ceased hostilities with the denizens of Salina Prime. However, word of the war's end reached the Strategic Command Complex too little too late and several Series-5 missiles were launched accidentally. Strategic Command sent out an order to terminate the weapons' mission, but only two missiles were known to have recieved the order and crashed upon an uninhabited planet. One of the missiles detonated whereas the other became embedded in rock. The surviving missile sent out a distress signal that was picked up by the USS Voyager, still on its long journey home to the Alpha Quadrant. Ensign Harry Kim and The Doctor beamed down to the planet where they found the device, unsure of what it was, but the Doctor was able to communicate with it and stated that the machine believed itself to be organic and was in a state of panic, thinking that it had been blinded and lost its limbs. The Doctor had the device beamed to Voyager for analysis and managed to build a rapport with it, but he soon became outraged when the crew discovered what the device was and intended to destroy it so that it would no longer pose a threat to anyone. He argued that even though it was a machine, the weapon was still intelligent and had a right to live. Since the weapon had apparently lost all memory of its mission, it was decided that the crew would help to separate the intelligence from the missile and preserve it.
The warhead AI possessing the Doctor, played by Robert Picardo
A short while later, the Doctor, Ensign Kim and Lt. Torres attempted to separate the missile's AI from the warhead. The AI seemed to regard their actions as hostile and armed itself. The intelligence then hacked into the Doctor's holographic matrix, taking over his body. The missile seemed to recall its purpose and demanded that Voyager take it to its target: Salina Prime. Captain Janeway complied with the AI's demands but made every effort to stall its progress until the crew could find a way to outsmart this "smart bomb" and rid themselves of it without letting it reach its target.
Ensign Kim and Lt. Torres were trapped in sickbay with the missile and Kim attempted to convince the AI not to blindly follow its program. Eventually, he assisted the intelligence in finding an error within the missile circuitry that caused it to crash, which turned out to be a termination order stating that the Druoda's war was over. The AI verified the order and realised that it no longer had a mission, however Voyager had encountered several other Long-range tactical missiles that had intercepted the ship in order to retrieve their missing number. The AI relayed the termination order to the other missiles, but they had already recieved them after crossing their programmed targetting threshold, meaning that they could not be diverted from their target once they were within two light years of it.
The AI possessing the Doctor informed Ensign Kim that it could stop the other missiles by detonating itself and taking the others with it. Hesitantly, Kim reintegrated the AI matrix with its platform and beamed it into space. The missile was tractored by one of its fellows and they all jumped to warp. The missile then detonated, destroying itself and all the others, preventing another needless war.