A launch key is an electronic code key used in the activation of nuclear ordnance aboard a vessel or other military installation. Launch keys issued to seaQuest DSV 4600 command-level officers appear to be made of metal, featuring the picture of the wearer on the bow and an engraved barcode on the blade's front, with a circuit trace pattern on the reverse. They are typically hung on ball chains around the wearer's neck as part of their uniform.
In 2017, Captain Marilyn Stark made use of her launch key to arm the thermonuclear ordnance aboard the Nor-Pac submersible seaQuest DSV 4600 during what became known as the Livingston Trench Incident (DSV: "To Be or Not to Be").
In 2018, Dr. Rubin Zellar forces Captain Nathan Bridger and Commander Jonathan Ford to use their launch keys to activate seaQuest's nuclear ordnance, suggesting that a two-key system was established following the Livingston Trench Incident. Zellar is unaware that Bridger disabled the nuclear warheads prior, realizing that seaQuest's firepower was his goal (DSV: "Games").
Later, Bridger and Ford use their launch keys to activate the entire explosive ordnance of seaQuest to close a catastrophic schism in the sea floor caused by the World Power operation, resulting in the ship's destruction (DSV: "Higher Power").