Twelve years ago, Hadrian Spooner founded the company HMS Engineering with his friend Mark Haile, deep in the Shire of Hereford. Hereford isn't exactly start-up country, but it's the perfect place to use inexpensive farmland as a base for working as a metalsmith, making extravagant metal instruments.
Hadrian, 49, had already told me on the phone what kind of stuff he and his friends were designing and building: amphibian snowmobiles that can traverse the Bering Strait, home-made locomotives, and hail-disruptive vortex cannons.
As a scientist at Oxford, I happily took the opportunity to leave my laboratory and take a tour through the hilly hinterland that inspired J.R.R. Tolkien's Shire (Middle-Earth). The plan was to visit the metal druid Hadrian, on assignment from Motherboard.
After driving through the enchanted valleys for several hours, I finally arrived at Hadrian's workshop in the hills of Herefordshire. Here, a world of wonderful prototypes, which totally could've been the work of tinkering gnomes, was revealed. I was greeted with Snowbird 6, the first to cross the frozen Bering Strait during the expedition Ice Challenger in 2002. In two giant halls, I found a stripped Hummer chassis, an ancient circus wagon, and a few decommissioned cruise missiles.
Of course you could use it as a weapon, but it's much more fun for shooting holes in the woods.
But the main reason I had come was something else: a cannon that can shoot gas rings at clouds.
The hail cannon is one of Hadrian's favorite projects. When asked, he enthusiastically explained the inner workings of his cannon, and he also proudly presented it at the annual Welland Steam Ralley, a meeting of steam engine enthusiasts in Worcestershire (the county known otherwise for its eponymous sauce):
The hail cannon's shots actually look completely nondescript at first; only upon closer inspection can you detect the almost majestically floating ring of air. But the sound is all the more impressive. It sounds like a sonic boom flying right past your ears.
The cannon creates an explosion by mixing the gases acetylene and oxygen. Once ignited, the hot, gaseous mixture expands in the barrel, forming a traveling ring. According to Hadrian, the rings from his cannon reach speeds of up to 300 kilometers per hour.
Hadrian told me that he's always been a hobby tinkerer and that he always loved extraordinary projects, from houseboats and special vehicles to vortex cannons. Studying anything other than engineering was out of question for him. While he learned his craft, he met his buddy Mark, with whom he later founded his tinkering company. The workshop has also become the final resting place for a few of his proudest inventions. Hadrian presented them to me during a tour of the premises:
When I asked why of all things he decided to build a vortex cannon, Hadrian replied: "We just like to play. And when the BBC asked us if we could build one for their space shuttle documentary, we didn't hesitate for a second. Of course we got to shoot at clouds with the cannon first!"
The main reason the vortex cannon is also called a hail cannon is that American farmers enjoy shooting at clouds with them. They believe the cannons can disrupt hail storms, which often ruin their crops.
The hail-vortex cannon also used to enjoy wide popularity in Europe. French winegrowers, in particular, used them in the early-20th century to protect their grapes from hail. In southern Germany, some vintners still have them in their fields.
Only one other specimen that can shoot with the same impact as his cannon can be found in Europe these days, Hadrian said. He designed and built both. And not because it hails a lot in his region (rather, it drizzles incessantly); he was contracted by the BBC for a TV production.
The tinkerer didn't think twice before designing the cone-shaped cannons. But the construction is not hazard-free. On one occasion the gas mixture exploded, causing fiery chaos on the courtyard, Hadrian recalled.
Acetylene is a highly explosive gas. A teeny-weeny spark from a zipper, for example, can be enough to ignite it, Hadrian explained. Acetylene is mixed with oxygen and filled into a little chamber at the bottom of the cannon. The the mixture is ignited by two spark plugs.
The ring is created in the same way that cool smokers make them when nobody's talking to them, just like the volcano Etna on Sicily (see video below): Air is pushed through a tube under pressure; the air drags on the walls of the tube. So the air flows faster in the middle than on near the walls. That's how the ring forms.
Here is a clip of one of Hadrian's cannons in action. You can clearly see the ring. On top of that you get to discover just how enthusiastic a BBC reporter can become:
These images show how much power the ring can generate. This rare video of Mt. Etna shows majestically floating vortex rings created by the volcano:
The successful abatement of hail by means of a vortex cannon is scientifically questionable and has never been demonstrated conclusively. However, the US Army began researching the potential use of vortex guns (vortex ring cannons) as a non-lethal weapon in 1998.
The Fraunhofer Institute was also contracted by the German Ministry of Defense and, until at least 2003, tested vortex generators as part of a project for the development of non-lethal weapons. The Ministry of Defense didn't reply to our inquiries into the current status of vortex research in Germany, but the website of the chemical technology division of the Fraunhofer Institute still lists a project to research non-lethal weapons. In response to our inquiries, the state-funded German Research Institute said that, to date, they are still researching vortex cannons for military use and for use by law enforcement in public spaces.
The US Army's research demonstrated that even if you could create rings that could reach their theoretical maximal velocity (the speed of sound), the vortex wouldn't be strong enough to impress people at a distance, as was hoped.
Hadrian and his crew don't care. Nobody has dared to stand in front of their cannons yet. "Of course you can use it as a weapon," he said. Mocking the military use of the vortex, he added, "It's way more fun to poke holes into a forest." But unless you build a vortex cannon, the rest of you amateur tinkerers will have to continue firing well-aimed smoke rings from a fat cigar as your only available vortex defense mechanism.