The extremely in-depth, informative and very geek-chic video entitled "Hybrid rocket engine with acrylic and gaseous oxygen" was posted by YouTube user Ben Krasnow who writes:
So, yeah, now you know how to create a hybrid rocket engine with acrylic and gaseous oxygen and can cross that item off of your bucket list. And if you'd like to check out more interesting and educational videos from Ben Krasnow, you can visit his YouTube page by clicking here.
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.