If Junior is looking for a spectacular science fair project that can be built at little expense, but still uses a slightly dangerous chemical, he can’t go wrong building this real submarine, according to plans contained in the August 1940 issue of Popular Science.

When released in the local pond, the submarine repeatedly submerges and surfaces, all the time moving forward in the water. The secret of all of this is a small amount of calcium carbide, the same chemical used in old-fashioned miner’s lamps. When the chemical is exposed to water, it generates a high pressure gas, which is used to propel the vessel and provide buoyancy. The chemical is readily available at Amazon, and probably at your friendly local hardware store.

School will eventually reopen, so your young submariners can take advantage of their summer vacation to build and test the craft, which can be made out of scraps of sheet metal and tin cans. Soldering is required, but kids naturally enjoy working with molten lead. When school reopens and the science fair is on, the submarine can be used for a variety of scientific experiments involving buoyancy, propulsion, or chemical reactions. The teacher has probably seen old movies with miners wearing headlamps, but this will probably be their first exposure to the actual chemical used. A blue ribbon is almost guaranteed.