God’s Van de Graaff Generator


The Van de Graaff generator is the most entertaining piece of kit in any high school physics lab.

In general, soldiers aren’t stupid. We weren’t necessarily the smartest kids on the block, but it never was really a lack of intelligence that got us into trouble. It was rather the synergistic combination of some fairly difficult technical tasks combined with a lot of pressure and a healthy sprinkling of testosterone. The pressure was an integral part of the equation. Combat is stressful, so the Big Green Machine did its utmost to prepare us for that.

Uncle Sam had lots of stress enhancement tools. Sleep deprivation was the most common. It didn’t cost anything, and it worked like a champ. A little hunger added flavor. The real engines behind the chaos, however, were the Black Hats, ranger instructors, drill sergeants, and the like. They were harder than woodpecker lips and absolutely merciless. These guys can smell weakness at a slant range of three clicks in hard dark. Tying a knot in a piece of rope while sitting in your living room watching Netflix is painless. That same task dangling from a cliff with these sadists screaming at you is another thing entirely. It’s supposed to be hard. It’s their job to make it so.

The Boeing CH47D Chinook helicopter is a lot of cool things. It is also the
mother of all Van der Graaf generators. Photo by Daniel Klein via Unsplash

The Setting

I was flying in support of Air Assault school. Air Assault teaches operations in and around combat helicopters. Descending out of a hovering helicopter on a rope is a perennial crowd pleaser. Learning how to prep an external sling load is another. There’s a great deal of physical training along with some legendary ruck marches thrown in just to keep things spicy.

If something is too bulky to fit inside the aircraft you just rig it up with some heavy nylon slings and hook it underneath the helicopter. This day, we were a flight of two CH47D Chinooks. The loads were Conexes, those big steel boxes the Army uses to hold just about everything.

The six 30-foot blades on a Chinook helicopter are made from fiberglass. When slaved to 9,000 shaft horsepower worth of Lycoming fortitude they will move a simply breathtaking volume of air. They also collect a fair number of electrons.

The physics lab counterpart is the Van de Graaff generator. American physicist Robert J. Van der Graaff thought this rascal up in 1929. This delightful trinket sports an electrically-driven belt and a big silver Kojak ball up top. Turn it on and the thing builds up a massive static electrical charge. Grab it and your hair will stand straight up. Put one hand on the ball and touch a buddy and that guy will reliably come to Jesus.

Lighting is undeniably pretty, but you really don’t want to get any of that on you.
Photo by Brandon Morgan via Unsplash

A Van de Graaff generator instantly transforms the skinniest Physics nerd into an acne-ridden, lightning bolt-shooting god of thunder. It was the highlight of my high school physics experience. A Chinook helicopter in dry air is the same thing — only way more so.

Uncle Sam knows this, so the first step whenever you are hooking up a sling load is to touch the cargo hook with a grounding pole. As the aircraft in flight isn’t grounded and the tires are rubber this zillion-volt electrical charge is harmless to the flight crew. However, grab that hook without grounding the aircraft and you’re in for the ride of your life.

We had been picking up those big boxes for an hour or more. Our station was shut down for a few minutes while they cycled in another group of trainees, so I pivoted the aircraft to give us a clear view of the other bird, set down, and pulled the engine condition levers back to save gas. That’s when I saw it.

There were two guys standing on top of the big steel box as our sister aircraft maneuvered into position. This was the era before Kevlar so they both wore WW2-vintage steel helmets. I noted to my fellow pilot that neither man had the grounding rod.

It’s not necessarily that these guys were stupid, though that could quite possibly have been the case. They were just stressed and forgot something important. Before I could get on the radio an arc of static electricity several times brighter than the sun leapt from the cargo hook into the nearest man’s head.

This poor slob convulsed and flew backwards like, well, he had been struck by lightning. He dropped off the tall metal box and began flopping about like a beached carp. I could swear his uniform was smoking.

After a few minutes they got him up and walking, albeit at a pronounced list. In classic Army fashion, the instructors put him at the back of the line to try once more. I bet he never forgot that grounding rod again.

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