How to stop a 4000km/h vac-train with an elephant and a rubber band

Some time ago, when I started talking about blowing things up, I made an off the cuff remark about “…  if you want to bring down a flying city with exploding pigs, or stop a 4000km/h (mph … whatever) vac-train with an elephant and a rubber band.”  As it turns out high speed vac-trains present an enormous number of safety hazards. This is excellent news for the writers but not so great for anyone on board. There was a nice article on Gizmag that made a nice bridge between the physics (not too much) of what was going on and an intuition of why we don’t have these beauties yet. But you’re a writer – why worry about these details?

Elephant, Scifi explosion, Modern Cavedweller Actually, I think that this article could provide a good guide for writers. It identifies the technical details, that your audience may not necessarily want or need, and goes straight to the intuitive understanding of the current limitations or fundamental, and potential fun-depriving, problems facing this concept. Obviously, the enormous cost is a second order problem if you’re writing, so unless capital expenditure is central to your WIP, let’s move on. Take a look at the article and keep it in mind when you are researching anything related to use in your writing. I tend to think about science and technology, as this is my background but I would say the same applies nearly all the time. A solid high school level of whatever subject you’re researching is enough to make sure that your reader doesn’t stop suspending belief.

OK. So today’s challenge is an elephant and a rubber band vs a Vac-train. Obviously, there are many things that we could do, so the first step is to put some constraints on how we want this to pan out. Do we want the character(s) to die? What about the elephant – is it expendable? Let’s go for total destruction because that’s always the most fun! Have you ever been in the back of the bus and slid back and forth as the bus goes around the hairpin bends when you’re coming down icy mountain roads? The trick is to give a little impulse to the bus’ outward momentum and see when we lose traction and fall down the mountain …

Contrary to popular belief an elephant’s skin is quite sensitive. Really! What we need then is a long clear section of the Vac-train and take the elephant to one end – some grass will help coax it along. Once there, aim the elephant at the end of the carriage and wait for the next corner. Now, take out your rubber band and flick that elephant in the arse. You can shout as well but that is primarily to make you feel more like you’re actually doing something. The elephant will take off and even over a relatively short distance, 20-30 meters, it should reach a speed of over 20km/h. If you got yourself a good African elephant, you now have around 5 tonnes running through your Vac-train at a little over 5m/s – this means we have a kinetic energy of nearly 80kJ. That’s not as much as it sounds – around 20 grams of TNT – if that makes any sense, or the equivalent of driving your car into a wall at 45km/h (28mph). Also, the elephant and the train are going in the same direction. Is this enough? Probably not, and in any case, we’re already thinking about things in too much detail.

Let’s try plan B. Turn the elephant around to face the front of the train. Flick the elephant again with your rubber band. Now the elephant may not have had enough of an impact to derail the Vac-train but the chance that the driver’s cabin is solid enough to hold back your charging beast is minimal. In this instance we find a beautiful marriage between science and nature as the elephant crashes through the wall crushing the driver and initiating the emergency braking system. This has the added advantage, possibly, that your characters survive to annoy you another day. There is also a small chance for the elephant as well, which is always nice. All that remains is for you to work out how to get the elephant on the train in the first instance.

About Harry Tuttle

Harry Tuttle, part enigma, part machine, mostly confused and trapped in modern life. I think. I read. I write. Science Facts to Science Fiction and Beyond.
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