At night, sometimes, when the room is dark, and you turn the switch to the porch light on or off, you see a small spark inside the switch, behind the cover plate. These things usually occur when there is too much light to see them, so we don't even notice them. We don't think about the fact that sparks happen most of the time when we flip a switch.
The switch to the garbage disposal in your kitchen at home probably gives off an even larger spark, especially when you turn it off.
On the submarine we turned very big switches on and off. Huge arcs jumped off the switch contacts. These arcs, much too big to be called sparks, were hot enough to ignite flesh.
Most of these special switches were located at the end of long levers, and the arcs were funneled through ceramic arc chutes, away from vulnerable equipment and people. This gave the energy of the arc a chance to dissipate.
DC, or Direct Current, circuits tend to arc at the switches more often than AC (Alternating Current) circuits such as the ones in your house. AC Voltages drop to zero 120 times each second, giving a spark a chance to die before the air in the gap ionizes. The submarine used DC, almost exclusively. We arced a lot. Most of the time, the arcs were contained by the arc chutes.
Sometimes we had to open or close a switch under extremely high loads from our main motors. A 2,400 horsepower motor running at full power carries a very large inductive load that just does not stop simply because a switch is opened. The rheostat on the motor field winding must be lowered to its lowest setting before the switch is opened. On the newer submarines, this process was automated. But on our old boat the only safety measure was a "Stop and Think" latch on the switch.
It was hectic in the maneuvering room when we entered port. The submarine, even with two propellers, was not very maneuverable on the surface. The main motors were often used with one running ahead full and one running back full, to try to twist the submarine around in the harbor without moving forward or astern. It was common to switch a motor from Ahead Two-Thirds to Stop to Full Astern in three seconds or so.
Sometimes, when one of the Maneuvering Electricians was running the field winding rheostat with one hand and the big lever switches with the other hand, and hitting the Stop and Think Latch at the same time, he got a little bit off in his timing. When that happened, we got fireballs.
The purists among you will say that these were technically known as plasma. We were not particular about the terminology. We just stayed the heck out of the way whenever a fireball wandered through for a visit.
A fireball took on a life of its own once a it escaped from the arc chute. A ball of ionized atoms, no longer in molecular form, gets to go anywhere it wants.
The first fireball that one experiences tends to create a sensation of mindless terror. As much as they warn you about it ahead of time, it is difficult to maintain composure as you watch your first non-atomic mass wander around unrestrained, especially in the confined environment of an old submarine. After you have seen several, though, you realize that it is possible to co-exist with them. It just takes a slightly different level of consciousness than you expected to have to use in the military.
The pattern that I noticed was that fireballs tend to follow the path of least electrical resistance. The stainless steel trim strips at the edge of all the equipment, and along the deck and around the walls, provided a good path for the fireball to wander around. It was possible to stand on the linoleum decking, perhaps steadying myself with a hand on a formica surface, and watch the fireball wander around the compartment.
As with many other things aboard the boat, we tended to anthropomorphize fireballs. They were mobile, and they were dynamic, and they seemed to follow a decision-making process. Whenever a fireball came to an intersection in the stainless steel trim strips, it had to decide which way to go next. It was actually sort of interesting to watch, if you could manage to avoid messing your pants.
Come to think of it, a fireball seemed to have the personality of an independent housecat.
When the full, and fully qualified, crew was running the boat at sea, fireballs were simply another survivable phenomenon in our admittedly bizarre existence. In port, at night, with only one watchstander on duty below decks, it was another situation entirely.
One evening in port, after the evening meal and before the movie, we needed to switch from ship's power to shore power. We were going to remain in port for a couple of weeks and we wanted to give our battery a rest. The only electrician in the duty section took the duty torpedoman along to help him make the switch. I was the duty officer, and I was busy doing some paperwork, so I decided not to go along.
A few minutes later the lights went out, as expected. However, the boat stayed dark. The lights did not come back on after a few seconds, when they were supposed to.
Five minutes or so later the electrician showed up with his head hanging down. He was leading the torpedoman by the hand. The torpedoman's eyes were bulging and glazed. His face was pale. His breathing was erratic.
I pointed to the torpedoman and I asked the electrician, "Is he all right?"
The electrician replied, "Oh, yes sir. He's fine."
After a long moment of silence I asked the electrician, "Do you need to tell me something?"
He hung his head even farther and he said, "Mr. Charlton, I, uh, I just melted the shore power connection."
Our torpedoman had just witnessed his very first fireball.