Seems like the comments are very technical so for those in the know enjoy.  (I just think this is cool regardless!)

Here is a bit of an intro from the inventor:

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.