Diary of a Pyro

Copyright © 1988 - 2005 John H. DuBois III

Chapter Twelve

On New Year's we made, among other things, a number of skyrockets with the CO2 cylinder sort of report on them. A couple were small engines with a single report, and two were large D engines with three reports and an extra long stick for guidance. We didn't have any tube to launch them from, and after a futile search for a good trough formation in the oceanside rocks, we ended up just leaning them against a rock. We suspected that this would not be sufficient, and indeed it wasn't. Both of the large rockets fell to the ground immediately after beginning their ascent, and fizzled at our feet. We were in a small triangular area bounded on two sides by small cliffs and on the third by the ocean, so we couldn't run. When the charges went off all we could do was cover our faces and turn away and hope we weren't hit by anything. We weren't. In the morning we found engine casings with metal shards blasted into them.

Later that month we received our first shipment of chemicals, particularly those necessary for making flash powder. Finally we had all of the flash powder we wanted, and would never again have to mess with metal containers. We eagerly mixed up our first batch of flash powder, hoping that we had it right. We set a spoonfull out and lit it, and were elated when it disappeared instantly in a flash and puff of smoke. Luke filled up some cardboard tube sections and we went out to Pebble Beach to test them.

They worked perfectly; our homemade powder was just as good as the commercial stuff. The last ones we tossed out the window of Scott's car as we were leaving, much to his displeasure since he kept seeing security patrol trucks. Then we saw one headed quickly in our direction, so Scott slammed down the pedal of his Mach One and we headed in the opposite direction. Of course the roads of Pebble Beach and 17 Mile Drive are among the twistiest in the world (they are supposed to be “scenic”.) And, unfortunately, this vehicle had one problem: there was a bad connection to the high beams, so every time we went over the slightest bump they went off for a moment! Thus, the choice was between flying along a road full of hairpin turns using only the low beams, or using the high beams and just praying every time they went off. Needless to say, we escaped (we exited via the gate, hoping they wouldn't be on the lookout for a blue Mach One.) That was an experience I will never forget.

Rocket Engines

Luke had also bought some ammonium perchlorate to make rocket fuel with. Years before he had bought some polyurethane, the other component, but had never acquired the perchlorate to mix it with. Finally we had it. I figured out the proportions, and he mixed some up and loaded it into three ¾″ pipe sections. He put spindles up the center to make cores that would extend the full length of the engines. Though he didn't tell me until later, as the fuel cured it expanded for some reason and oozed out of the ends. He didn't realize that this indicated a problem and so just cut off the excess when it was hard. When it was done he capped one end of each, and drilled various size holes in caps to make nozzles for the other ends since we had no idea what size hole would be appropriate.

The fuel somewhat resembled the mix used for the Space Shuttle's solid rocket boosters (SRBs), which use polybutadiene, ammonium perchlorate, and aluminum. I had told Luke that the SRBs are ignited from the top, so that the flame produced shoots down the length of the core and starts it all at once. I advised him that I thought it would make no difference with engines as small as his, but he decided to light them electrically instead of with a fuse so that the igniter could be put up near the top. I made some igniters with leads long enough that they would extend a few inches out of the nozzle, where the ignition cable could be clipped onto them.

We brought the engines and some sticks to tape them to out to Del Monte Beach to try them. We pointed a tube out to sea and put the rocket with the largest nozzle into it. Remembering my safety precaution, I clipped the cable onto the ignition leads before moving to the other end of it and plugging it into the pocket timer/igniter I had brought. I then moved away to get a good picture of it as it launched. Scott or Luke pressed the button and ran. I heard the beeps and prepared to take a picture but nothing happened. Apparently the battery was too low. After a few more attempts we gave up and went home.

The next day we went out with good batteries and set it up the same way. Obeying some corollary to Murphey's Law, I forgot my precaution and plugged the cable into the ignition system first. Scott, Luke, and Laurence stood close by, while Matthew, perhaps having learned something from our previous experiences, watched from a distant sand dune. I was standing right next to it, my fingers mere inches from the nozzle as I blithely clipped a lead on to a wire dangling from the engine. Then I took the other clip in hand, squeezed it to open its jaws, and touched it to the other wire.

The air was split by a thunderous explosion, and I was knocked backward by the blast. Incredibly, I was still standing as were the others. Pain stabbed at me from various parts of my body, particularly my hands and my left arm and leg. I numbly held my hands in front of my face and watched the blood flow and drip onto the sand. Though my ears rang deafeningly and I could hear nothing, I remember saying “Oh shit, what the fuck have I done now?!” I looked about and saw the shattered rocket stick lying with the shredded remnants of the tube.

The others, miraculously, had not been hit by so much as a speck of galvanizing zinc. They walked over and tried to help me. Luke gave me his shirt to wrap around my hands. We made our way back to Scott's VW Bug, which naturally refused to turn over and had to be push started. On the way to the emergency clinic, which was quite a distance, I began to get my hearing back and, since I could not think clearly, asked the others to come up with a story to tell the admissions people. Oddly, they didn't think I would even be asked what had happened, but I insisted. Since Scott had been working on his car, he suggested that I say that I had been working on the ignition system of an engine when the exhaust manifold exploded. Though Scott had certainly not intended it that way, I later realized that this was almost comically accurate; after all I had been hooking up the ignition leads to a rocket engine when it exploded, and the nozzle (exhaust system) that my hands were under had undoubtedly done the most damage to me as it was blasted into bits of hot shrapnel.

I remember walking in the entrance to the clinic with Luke's bloody shirt wrapped around my hands, dishevelled and wearing a windbreaker with newly ripped up sleeves, and saying, “Hi, I need some help.” The nurses took a look and called for a doctor. While waiting, one of them took down various information and questioned me several times on the status of my insurance. I had no doubt whatsoever that I was thoroughly insured and so repeatedly assured her of this.

A doctor was soon picking bits of metal out of my hands as I lay on a table. He did indeed ask me what I had been doing that had put me in this state, and I made vague references to an exhaust system. I don't think he believed the story since he made various comments like “Hmmm… these almost look like pieces of a pipe bomb…” (that being precisely what the “rocket engine” had inadvertantly turned out to be).

Bandaged Arms

A couple of tendons had been cut by pieces of metal; he put a few stitches in one that was almost cut through before sewing up my hands. He put a splint on that finger to prevent me from moving it. Also, a slab of hot metal seemed to have shot down the left sleeve of my windbreaker. Certainly, something ripped up the sleeve near the wrist and took a large patch of skin off of the underside of my left forearm, so that that arm ended up being wrapped with bandages. However, there was no exit hole in my sleeve, so I'm not sure what really happened.


Bent Keys Though my left leg hurt quite a bit, there turned out to be nothing there but a bad bruise and slight cut. The doctor jut put a Band-Aid on it. I thought that perhaps a piece of metal had hit flat against it, preventing it from penetrating, until I was walking out of the dispensary with my codeine and felt bits of stuff falling down my pant leg. I pulled my keychain out of my pocket, which was directly over the bruise, and found that my keys had been mangled and the plastic cladding had been broken off of my pocketknife; it was pieces of cladding that I felt trickling down. Amazingly, I had been fortunate enough (given that a piece of explosively propelled metal was going to impact my body) to have it hit over my pocket, where my keys and pocketknife protected me. Although they had been rendered useless, I kept them for good luck.

Several weeks later, after the splint was removed, I noticed a bump that it had covered. It turned out to be the piece of metal, about ″ (1cm) square, that had entered my hand and cut the tendon. Apparently the doctor had not noticed it when he was working on me. By then my hand had healed, and when I pointed it out to the doctor he said “Oh, don't worry about it. People walk around all their lives with bullets in them without any problems.”

I ended up with $700 in medical bills (a lot of money for me at the time - remember, this was 1986!), and was surprised when my father told me that I had a $1000 deductible on my insurance. Perhaps the uneventful nature of my life (health-wise, at least) had lent a false sense of security. In any case, being of limited means (full-time student and unemployed), I offered the hospital monthly payments, and sent them an initial $50 payment. They found this unsatisfactory and were soon sending me dunning notices replete with friendly warnings about the state of my future credit record, etc., and letting me know that I would soon be the target of a collection agency. This went on for some time before they sent me, unsolicited, information on “Hill-Burton funds” which they could use to pay my bills. Apparently this was easier for them to deal with than my payments. I applied for them and didn't hear any more from their collections department.

I later found that a strong magnet would stick to my hand, and used this feature for demonstration purposes. Only once have I come across a magnet strong enough to be dangerous. While at a party, I was reading an article stuck to a refrigerator with a magnet. I wanted to read the part under the magnet so I tried to move it. It didn't budge. I pulled harder, and it pulled the 'fridge door open. I finally managed to push it over to the edge of the door and pry it off. It was amazingly powerful; probably a samarium cobalt magnet. Without a second thought, I applied it to my hand. Although it was much heavier than any other magnet I had succeeded in sticking to my hand, it held itself on quite well. I wandered around waggling my hand at people until it began to ache. Then I tried to remove it. After distending the surface of my hand several centimeters outward, I decided that I had a problem. It seemed that my skin was liable to give way before the magnet did. After experimenting and worrying for a while and having several people say “I told you so”, I managed to slide it off sideways. My hand hurt for long enough that I'm more careful with magnets now.

Luke eventually told me about the way the fuel had expanded. He called the company that he had bought the polyurethane from, and they told him that if there is moisture present in one of the compounds, carbon dioxide bubbles will form when the curing agent is added and will turn the result into polyurethane foam. The moisture may have gotten into the polyurethane itself in the years that Luke had it around, or it may have been present in the ammonium perchlorate. In our case the bubbles were so tiny that they could not be seen, but they effectively vastly increased the surface area of the fuel, making it burn so fast that it acted as an explosive. Oddly enough, the increased surface area leading to an explosion was similar to the problem I had had with the sulphur and sodium chlorate engine, the only other time I had been injured by a rocket.

I still don't know why the ignition system failed and fired the igniter as soon as I hooked it up. It may be that a stray static electric charge exceeded the dV/dt triggering threshold of the SCR, causing it to be activated as soon as the circuit was closed. It had never happened before, but then there would have been no point in a failure before since this was the first time I had used the ignition system with something that could seriously injure me. Forgetting my safety precaution, electronics that failed in the most disastrous way possible, and a rocket engine that turned out to be a pipe bomb… Murphey's Law in action.

Shortly after this episode, Luke and Scott went out to Fort Ord to hunt around again. Luke wanted some of the empty practice missiles to refill with various propellants; he hadn't been on the earlier trips. He brought back plenty of them, most of them ones with expended warheads but intact bodies. He also found two dud antitank missiles. He used pliers to peel off the metal from the warheads, and found in each a solid piece of high explosive (probably PETN) shaped like a diamond, but with an inverted cone-shaped section missing from the front. This was lined with a metal that looked like copper to form the shaped charge. One of the warheads, which had been badly damaged, had bits of rock embedded in the explosive. They also each had two detonators, which he removed. Since the explosives were not in a convenient form, Luke ground them up in his mother's meat grinder. I was far away when he did this. He mixed the powder with some picric acid he had around and we tried setting it off with one of the electrical detonators, but it didn't work.


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