We are fascinated by the hybrid rocket engine which [Ben
Krasnow] built and tested in his shop. It is actually using a
hollow cylinder of acrylic as the fuel, with gaseous oxygen as
an oxidizer. We’re already quite familiar with solid rocket
propellant, but this hybrid approach is much different. When a
rocket motor using solid propellant is lit it continues to burn
until all of the fuel is consumed. That is not the case with
this design. The acrylic is actually burning, but if the flow of
oxygen is cut off it will go out and can be ignited later. This
also opens up the possibility of adjusting thrust by regulating
the pressure of the oxygen feed. [Ben] milled the test rig in
his shop. It’s a fat acrylic rod through which he bored a hole.
There are two aluminum plates which complete either end of the
chamber. The intake has a fitting for a valve which connects to
the oxygen tank. There is a nozzle on the outflow end. Check out
the video after the break to see a full description. You’ll also
get a look at the