How do you test submarine launched missiles?

They are electronically tested while still inside the launch tube by Missile Technicians, for Ballistic Missiles aboard FBM submarines. Aboard Fast-Attacks, Torpedomen perform the same test on Tomahawk, Harpoon or Subroc missiles with an electronic diagnostic device. They are also actively tested by shooting exercise weapons at Naval ocean test ranges. This is how the boat and crew is certified for handling and launching the weapons it carries.

All test are performed inside the torpedo or launch tube. This is a direct result of the sinking of the submarine Scorpion in 1969. Though there continues to be speculation concerning her fate, one major conclusion was that she experienced a torpedo "hot run" - the term for a torpedo activating inside the torpedo room. In those days, the old Mk 37 torpedoes were also electronically checked, but they had problems with hot runs. Until the Scorpion accident, no previous occurrence had led to a casualty.

The primary evidence for a hot run scenario was her location and course on the bottom of the ocean. At the time, she was transiting home after a long Mediterranean deployment; when found, she was almost 180 degrees off course. This is consistent with torpedo shut-down procedures in a hot run scenario. All torpedoes have range activation features to keep them from becoming active too close to the shooting submarine - being sunk by your own torpedo was a big problem for US boats in WW2. In fact, the USS Tang was sunk by an errant torpedo.

One feature to deactivate the torpedo is to turn 180 degrees - if a torpedo errantly turns 180 degrees, it will automatically shut down before arming. The fact that every compartment of the Scorpion except the Torpedo Room was crushed meant that the TR was already flooded - meaning that they failed to shut it down before it armed and detonated.

After that, testing procedures for all weapons were changed so that required checks had to be performed inside a tube to eject a hot running weapon. However, the safety record of the current Mk-48 torpedo led the Navy to remove HR procedures over 20 years ago, when I was still riding boats.