I was around 15...
I grew up out in the country in Oklahoma and as a budding pyromaniac I LOVED model rockets... but 'normal' model rockets were boring to me... I had to weaponize them....
I had made a few small rockets using Estes rocket kits... and I had even put some small explosive charges in a few... In earlier years I had disassembled fireworks for my explosive endeavors, but since I had a beard I could go into a gun store and buy smokeless powder by the pound- (heck, given it was Oklahoma in the 80's I probably didn't need the beard), and my dad- A physics professor at the local university had given me permission to buy chemicals from the University chemistry storeroom (NOTHING like that could happen today, I am fairly certain)...
Armed with this capability I decided to build my masterpiece- A heavy lifter that could loft a truly massive pyrotechnic payload high up and detonate it...
I drew diagrams, and plans- looked up thrust and determined how massive the payload could be... I was looking to create a massive display- something between the destruction of the Death-star in 'A new Hope' and the the destruction of the Death star in 'Return of the Jedi' ...
I carefully constructed a massive rocket maybe 1.5 feet long... At its base were 7 D-class engines (1 central engine, 6 more in a hexagon around it)... The body was reinforced with epoxy, as were the balsa wood fins... a lot of work went into the rocket, but more went into the payload- The top 8" had a massive charge consisting of smokeless powder, various components salvaged from commercial fireworks, and- and this was the best part- hundreds of pieces of small magnesium metal shavings.
My friends and I gathered in my bedroom/workshop- and the consensus of the peer review was that the rocket was a revolutionary design, and technically 'kicked ass'... Not only was it flight-worthy, but it should launched with all due haste so that it's awesomeness could be carefully evaluated as soon as possible...
So we slipped it out of the house past my mother in a plain paper bag- and took the jeep out to the cow pasture and commenced to prepare the launch pad.
It was a cold day in early winter, the grass was brown... About 8 cattle followed us in hopes we were going to feed them a bag of cattle cubes- we drove to the middle of the main pasture which we judged to be a good spot with perfect view of the sky... this sucker was going to go REALLY high really fast!
Wiring the engine igniters took a while, and the cattle - having determined that we were not bearing any tasty treats- lost interest and started to graze nearby.
Once wired up, and the wires taped carefully in place we set up the launch pad- a metal plate for the rocket to sit on and a metal guide rod that slipped through a small straw affixed to the side of the rocket to ensure the lift off was vertical.
As we were pushing the guide rod int the dirt it hit a rock and bent... there was much cursing from the launch technicians and we spent many precious minutes of our launch window straightening out the rod as best we could... finally we got it mostly straight- with just a slight kink in it- the launch director (me) determined it was good enough and decided to proceed with the launch.
(The post-launch failure analysis determined that this decision was probably the cause of failure, and not only led to the loss of the vehicle, but nearly lead to the death and/or injury of the ground support crew. The review board noted that the chain of events that followed could have been largely avoided if the countdown had been paused until a new rod could be found.)
The rocket was transported to the launch pad with great ceremony, and slid down the rod- the ignition wires were hooked up to ~20 feet of speaker wire and the other end of the wire was brought back to the car. The hood was opened and the wire was brought up-- After a brief countdown the wires were touched to the battery terminals.
(NOTE: The following description of the sequence of events has been pieced together from eye-witness accounts, as well as careful analysis of the debris by the engineer)
T=0s : Massive sparks as the wires made contact with the battery- immediate ignition of most- but not all- of the 7 engines.
T=-0.267s The rocket, with unbalanced thrust, rapidly jumped up 8" and stopped as the straw got caught on the kink in the guide rod.
T=-0.267s to T=-1.5 s The super-heated rocket exhaust ignites the dry grass in a circle ~2 feet in diameter around the launch site, as well as ignites the remaining engines.
T=-1.5s The sudden increase in thrust allows the rocket to pull the guide rod out of the ground- liftoff proceeds...
T=-1.5s to T=-7s The rocket - now unbalanced because it has a metal javelin affixed to it's side- corkscrews wildly in the air, it's motion not only seems to defy laws of physics, but also seems to have malevolent intent as its zagging trajectory turns horizontal and turns toward the car. Teenage boys scream curses, lives flash before eyes as they dive down, some rolling under the jeep.
T=-7s just in time, the rocket takes an upward trajectory and then violently pitches down- it smacks down into the pasture abbout a 100 feet on other side of the car... driving the metal rod deep into the dirt.
The engines burn out, setting fire to more grass... then, after a split second of silence, the payload detonated with a "WHUMP!" White hot magnesium shavings spectacularly fly out and ignite everything in a 20 foot diameter circle.
The next 10 minutes were a blur during which teenage boys fight the resulting grass-fires... and cattle wisely ran away...
Once fires were extinguished, the launch personnel met to debrief, and to determine root cause of the failure... and MOST importantly to get our stories straight to explain our burned clothing to our parents.
The failure review board determined the likely cause of the launch failure, and all agreed that- despite the failure- that it was "Fuckin' Awesome", and that another heavy lifter should be constructed as soon as additional funds could be found...