[bert]

These rockets use a launcher fabricated from light weight polyvinyl chloride tubing. One end is capped and has a pizoelectric ignighter installed. The projectile is commonly rammed down the tube until it rests against a stop at the combustion chamber. An alchol based pressurized mist is sprayed into the chamber and ignited by the pizo igniter.

[FreePaul]

Sounds like our sodium metal mortors. They were more like 75mm since we used 2 1/2" and 3" steel pipe (long before PVC came along) and launched cans sometimes filled with flour. Made a big "smoke" cloud.