Up to Table of Contents


The first thing to remember about a submerged submarine firing a torpedo is that the stability of the boat is unlike the stability of a surface ship. On the surface, a ship is extremely stable fore and aft. Submerged, however, the stability fore and aft is almost non-existent. You never hear of a surface ship in good condition flipping end for end, even in the roughest of weather. A surface ship rolls from side to side, and on extremely rare occasion a surface ship in good condition rolls over so far that it sinks. A submarine on the surface has very similar stability characteristics to a regular surface ship.

Submerged, however, is a different world. The stability of a submerged, intact submarine cannot be described in the same terms as that of a surface craft. It has been a long time since I studied that particular course, and some of the terms are a bit vague right now. But what I mean is that the center of mass of the submerged submarine is below its center of buoyancy, instead of above it, as on surface ships. So the lateral stability of a submerged submarine is quite strongly positive.

All of which is to lead up to the fact that the longitudinal stability of a submerged submarine is minimal, and is always the diving officer’s second concern, with only the actual depth of the submarine of comparable importance. It is very easy for an inattentive submariner, using the diving planes, to tilt his boat fore and aft to an extreme degree, possibly losing control and sinking with all hands. It is also possible to get unbalanced fore and aft to an uncontrollable degree by shifting weight around inside the submarine.

Which means that shooting a 3,000-pound torpedo out of a bow tube or stern tube, if done improperly, could wreak havoc with control and survivability of the boat. So a strong water tank (the WRT tank) in each torpedo room is kept available for quick corrections to buoyancy problems caused by a torpedo shoot.


(This is from memory. This is not an approved checklist!)

(Kids, do not try this at home!)

(Also, this is for a WWII vintage, mechanically set steam-powered torpedo.)

(And please remember, I never actually did any of this. I just watched.)

1. Select the tube.

2. Wake up the three sailors whose racks are in your way.

3. Remove the racks, blankets, mattresses, pillows, etc.

4. Install the massive cradle supports. (Two strong people required.)

5. Unlatch the cradle containing the torpedo, and slide it into position directly aft (forward) of the tube bank.

6. Attach chainfalls to the cradle, fore and aft.

7. Hoist the two tons of cradle and torpedo, using manual effort on the chainfalls, into position inboard of the specific tube you are using.

8. Install another massive set of cradle supports.

9. Lower the cradle onto the supports and latch it into place.

10. Add the fuel (denatured alcohol) to the torpedo.

11. Add the oxidizer (compressed air) to the torpedo.

12. Remove the protective cover from the arming impeller.

13. Install the igniter in the warhead. Install the detonator.

14. Check the mechanical indicator to verify that the muzzle door of the tube is shut.

15. Open the valve to drain the tube to the WRT tank.

16. Listen to make sure that no water is flowing through the drain.

17. Check the sight glass in the breech door to verify that there is no water in the tube.

18. Have another qualified torpedoman verify your work to this point.

19. Call the Officer of the Deck, Submerged, (OOD) to request permission to open the breech door.

20. Wait for the OOD to obtain permission from the skipper to open the breech door, thereby breaking "rig for dive".

21. Shut the watertight door between the torpedo room and the forward battery compartment, just in case of a problem.

22. Use the approved wrench to turn the locking ring around the breech door until it no longer interferes with opening the door.

23. Use the large handwheel to undog the breech door.

24. Observe with relief (oops, I mean verify) that the tube is dry.

25. Send your most junior qualified person to quickly inspect a couple of important mechanical details inside the tube.

26. Remove the straps holding the torpedo to the cradle.

27. Using come-alongs, manually shove the torpedo into the tube.

28. Insert the target-setting shafts into the torpedo. Verify proper operation.

29. Shut the breech door and dog it.

30. Using the approved wrench, turn the locking ring to the locked position.

31. Open the tube drain valve (it should already be open, but you are just verifying it.)

32. Shut the vent valve on the WRT tank.

33. Open the vent valve on the tube.

34. Port compressed air to the WRT tank, forcing sea water from the WRT tank into the tube, filling the remaining void space in the tube.

35. Listen and watch for water to spill over from the tube vent valve, into the bilge.

36. Shut the compressed air valve to the WRT tank.

37. Shut the vent valve on the tube. (Note: Now the tube and the WRT tank are both connected via the tube drain line. But both are pressurized.)

38. Request permission from the OOD to open the muzzle door.

39. Using the approved wrench, turn the operating shaft to unlock the muzzle door. Move the hydraulic control valve lever to the OPEN position (Note: The muzzle door is no longer locked shut, but sea pressure is holding it shut.)

40. Using compressed air to the WRT tank, pressurize the tank/tube combination until the muzzle door swings open. (Note: We don't use compressed air directly to the tube, because we don't want to release a bubble of air from the muzzle door. That would give away our position.)

41. Shut the tube drain valve as soon as the muzzle door indicator shows fully open.

42. Shut off the compressed air to the WRT tank.

43. Open the vent valve to the WRT tank, releasing the air pressure into the torpedo room.

44. Open the compressed air valve to the firing mechanism.

45. Close the enable switch to the firing mechanism.

46. Notify the OOD that Tube #1 is ready to fire in all respects.

47. The OOD pushes the firing plunger in the conning tower.

48. The shafts that set running depth and angle of turn into the torpedo retract from the fish.

49. A pre-measured amount of compressed air forces the torpedo from the tube.

50. The engine-starting lever trips as the torpedo leaves the tube. It is easy to hear the torpedo engine startup. (Note: At this moment, the submarine loses 3,000 pounds of the weight of the torpedo, but gains 2,900 pounds of the weight of the water that rushes into the tube to replace the torpedo.)

51. The compressed air valve to the tube shuts quickly and automatically, and the automatic poppet valve opens, dumping the large air bubble to the WRT tank, which dumps the bubble into the torpedo room. Some water accompanies the bubble into the WRT tank.

52. Using the approved wrench handle, turn the operating shaft to shut the muzzle door.

53. Verify the indication that the muzzle door is shut.

54. Open the tube drain valve.

55. Open the tube vent valve. The tube now drains to the WRT tank.

56. Watch the sight glass in the breech door to verify that the water is draining from the tube.

57. Request permission from the OOD to open the breech door.

58. Request the trim manifold operator in the pump room to pump 3,000 pounds of water from the WRT tank to the forward trim tank.

59. Open the breech door, and begin drying and lubricating specific points inside the tube.

Note: The WRT tank could hold enough water for one or two shots. If three torpedoes were shot in quick succession, the WRT tank overflowed hundreds of gallons into the torpedo room bilge. A call to the watchstander in the maneuvering room could get your bilges pumped overboard (well, not directly overboard, but into the fuel oil expansion tank, a "soft" tank with sea water in the bottom and diesel fuel in the top.) But there is no meter on the bilge pump, so you don't know specifically how much water you need to flood into the forward trim tank to compensate for the weight of the water you are pumping out of the bilge. So you make an educated guess, and the diving officer must empirically determine the final correction, based on the action of the bow and stern planes in keeping the boat under control fore and aft.
Up to Table of Contents