.
In: 6
The simple answer is by using steam power to move a set of pistons in a long tube.
Interested bits start around 2:15
There’s a newer type that uses magnets, but old-school carrier catapults (from the 1950s to today) work with steam. Steam is easy to use on an aircraft carrier, because it’s powered by a nuclear reactor, which is basically a giant steam engine. Since the carrier is constantly making steam, you have a constant supply of steam that you can reroute to various systems around the ship to do stuff with. The catapult was one of those systems.
Steam can be pressurized to an incredible degree, as long as you build a strong enough steel tank to hold it. So the catapult is just a piston held inside a really really strong steel tank. You hook the airplane’s front wheel on top of the piston, then lock the piston in place. Then you pump steam into the tank – lots and lots and lots of steam, until the pressure rises to immense levels. Then you unlock the piston, and suddenly all that steam pressure has an escape route! It expands rapidly, forcing the piston forward at incredible speeds. The piston drags the airplane with it, and once it’s going fast enough, the airplane unhooks from the piston and flies away.
Since you’re five (or not)…
Water is really good at pushing things (because it’s a fluid that you can put under pressure but doesn’t shrink in size much if at all). Steam has that same ability to push things, but is much better at moving quickly in pipes and heating water to make steam is an easy way to add energy for pushing (pressure, up to 236 kg [520 lbs for fellow americans] of pressure *per square inch* in this system).
When the steam is released, it moves into the pushing pipe rapidly. It’s under a lot of pressure and has a lot of energy (the piston diameter is 18″ and π* r* r means the surface area of the piston is probably 254 sq in so it’s pushing with ~60,000 kg [~132,000 lbs] of force) and the airplane is free to roll forward. Given that the catapult is pushing 4 times harder than the airplane weighs, and it’s doing it for up to 250 feet, it’s going to go really fast somewhere.
Edit: sorry about mixing kg and sq in.
Steam pistons and hydraulic cylinders. A small volume of steam at extremely high pressure expands to many times it’s original volume when the pressure is reduced. That expansion pushes the cylinder which pulls the plane quickly down the flight deck.
Think of the fizzy overflow that happens when you shake a carbonated bottle. The small volume of co2 gas causes a large expansion when the bottle top releases the pressure inside the bottle.
Latest Answers