MEW
EASY,
I built one of those MEW co2 engine things that was featured in the back of a MECA newsletter about 4 years ago.
Had about -3 ounces thrust! I was afraid it was going to blow (going back to my younger days where a boy knew how to pack a Co2 cartridge with matchheads and gunpowder, doh!) but it just went "pssssssst" like a jetex but without the thrust.
Andrew