Sometimes you just build a rocket in your spare time. Or at least that’s what you do if you’re Valve hardware hacker Ben Krasnow.
In it, Krasnow shows off the “hybrid rocket engine” he built from an acrylic rod (which serves as the fuel source) and a few other parts. The way the engine is built allows Krasnow to throttle it and shut it off, something you can’t usually do with solid-fuel rockets. He writes:
I built a small rocket engine for demonstration purposes. The engine is built from a 2″ diameter acrylic rod through which I drilled a 0.5″ hole. The oxygen at 80 psi or less is passed through the hole and then is forced through a convergent-divergent nozzle at the tail end. The nozzle’s throat is about 0.25″ and expands to 0.625″. I lit the engine by inserting a burning cotton swab (with wooden stick) while a small amount of oxygen was flowing. The acrylic catches fire very easily in a pure oxygen environment. The engine can be throttled and shut off completely, which is a major benefit to hybrid engine designs. Solid-fuel rockets cannot be throttled or shut off, which makes them difficult to control.
Check out the awesome video above.