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Dear Evil Engineer: Could I engineer a storm of giant hailstones to teach my ex a lesson?

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The evil engineer gives advice on whipping up a storm of vengeance against a villain’s unfaithful ex-husband.

Dear Evil Engineer,

I recently divorced my unfaithful husband. I was given primary custody of the children in the settlement, as well as the shared missile arsenal and the megapython. However, my ex-husband has walked away with our rare koi carp collection, which we spent many years and tens of thousands of pounds curating together. Flying a drone over his new property, I discovered that he’s building a pleasure garden filled with koi ponds to show off to his lover.

I am even more furious than before. I’d like to get my revenge by killing the carp, but I need to make it look like an accident so I won’t look guilty and lose custody of the children. I’ve heard that it is possible to engineer the weather – would it be possible to generate a storm of giant hailstones above his property to kill the carp?


A jilted villain


Dear villain,

I’m pleased to hear your attitude towards your ex-husband has been so healthy since your separation. Some of the most memorable villainous schemes emerge from challenging personal circumstances like yours.

You are right to say that weather can be engineered, to a limited degree. In the 1940s, Bernard Vonnegut discovered that introducing silver iodide (normally used as an antiseptic) to a cloud chamber produces ice crystals, as cool water clings to these particles to form ice crystals at less frigid temperatures than would be required otherwise.

This sparked decades of weather modification efforts centred around cloud seeding: releasing silver iodide or other materials into clouds to trigger formation of rain, snow, and hail. Although weather modification is normally used to mitigate damaging weather, it has been used as a weapon in the past. This has been an exclusively villainous area of R&D since 1977, when it was forbidden by the UN under the Environmental Modification Convention.

If you want to harness hail as a weapon, it is useful to begin with understanding how it is formed naturally. Hail forms in cold, vigorous thunderstorms when an ‘embryo’ (such as a piece of dust) is lifted by a strong updraught and water freezes into layers of ice around it. This continues until its weight is greater than the force of the updraught and it falls towards Earth.

Larger hailstones form in stronger storms with large upward forces to support growing hailstones; you find stones of around 2cm forming in 40mph updraughts, 4cm stones in 55mph updraughts, and 10cm stones in 100mph updraughts. Giant hail is associated with ‘supercell’ thunderstorms, which are characterised by strong, rotating updraughts.

The larger the hailstone, the greater its kinetic energy and the greater the force exerted upon impact as it suddenly decelerates. A 4cm hailstone falling at a typical terminal velocity of 25ms-1 has about 10J of kinetic energy. An airsoft gun, which fires pellets with comparable energy, would be well beyond the acceptable limit for military simulation events and is anecdotally powerful enough to kill or injure a fish (depending on the fish). This is probably the smallest size you should aim for, given that a hailstone can be compressed more than a plastic pellet, and will therefore exert less force on its target than a pellet with comparable kinetic energy.

Now, plenty of effort has gone into altering the size of hailstones. Most attempts involve cloud seeding to multiply the number of embryos, distributing the water among more hailstones and resulting in smaller hailstones. However, while there is a precedent for artificially induced storms (the US attempted to prolong monsoons during the Vietnam War using cloud seeding and there are allegations that cloudionisation technology was deployed more recently to generate storms in the Arab Peninsula) there is no known technology for generating hailstorms specifically, let alone for generating giant hailstones.

A hypothetical hailstoneboosting technology would work by 1) decreasing the number of embryos (the opposite of cloud seeding); 2) increasing the volume of supercooled water in a storm; or 3) increasing the strength of the updraughts; or some combination of these. The most practical of these three very impractical options is probably option 2, although given the unpredictability of weather, there is no guarantee that you would get the result you hope for.

You already have access to a drone, so perhaps you’d consider using that to kill the fish? There are various substances deadly to koi carp which you could release into the ponds. For instance, carp are very sensitive to water conditions, so a small swing in pH (induced by adding some acid) could prove deadly, as would a small amount of copper, chlorine, iron, lead, or zinc. An investigation would probably attribute the deaths to carelessness on your ex-husband’s part.

You could also freeze the ponds with liquid nitrogen, or (if your drone can carry the load) release predators such as herons into the garden. If you are still wedded to the idea of killing the fish with hailstones, why not try dropping blocks of ice into the ponds via drone?

Although it is unlikely that the killing of the carp will unfold exactly as you hoped, this is a rare opportunity to get creative and execute a really ‘you’ evil plan, so above all remember to have fun!

The Evil Engineer

PS: Recent research suggests that climate change may already be causing more giant hail events, in addition to other types of extreme weather. It brings a tear to my eye to see humanity come together to slowly render the planet uninhabitable! It’s the sort of villainy I once thought confined to dystopian novels.

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