Ever fancied making yourself a pocket rocket engine for your homemade jetpack? Yeah, me neither, but it's totally possible, apparently. Ben Krasnow, one of Valve's awesome hacking engineers, shows you how.
What Krasnow made here was a hybrid engine, one that uses a solid fuel controlled by a flow of oxygen (two fuels in two different states), which regulates the burn rate, meaning you can easily throttle it up and down like you might a jet engine. It's the kind of thing that you could easily build into something like a jetpack, because it allows you to precisely control the amount of thrust, unlike your traditional ignite-and-watch-it-go rockets.