The U.S. Government Developed ‘Water Bombs’ After World War II
Surprise — it didn't work out
Aerial tankers dumping water on forest fires is now common practice, but in the early days, engineers tried different kinds of bizarre experiments … including exploding “water bombs.”
It’s not a bad idea … in theory.
During the 1940s, the U.S. Forest Service teamed up with the U.S. Air Force to find new ways to fight fires. The water bombs, had they ever been used, would contain forest fires that threatened timber supplies and rural communities, particularly in America’s western states.
The October 1947 issue of Popular Mechanics offers a small glimpse into this experiment. “Fighters and bombers that once spread fire and destruction are helping to drench blazes that yearly destroy 31,000,000 acres of valuable timber in The United States,” the magazine reported.
The Air Force and the Forest Service conducted the tests in Lola National Forest using two P-47 Thunderbolts and one B-29 Superfortress.
In contrast to meager pre-war efforts, like kicking five-gallon cans of water out of plane doors, the three planes at Lola drop water-filled auxiliary fuel tanks weighing 13,000 pounds and more on a single sweep. In the initial test three 4000 pound containers were attached beneath the B-29 and each P-47 carried a pair of 165-pounders under its wings. Tail fins and fuses added in Forest Service Shops converted the thin shelled tanks into bombs.
The tests involved several different kinds of bombs of different sizes, filled with water and various chemicals and set to explode at different times.
To evaluate aerial fire-fighting techniques, two of the big bombs had proximity fuses, set to explode over the target and saturate the flames. The third and all four and all four smaller fighter tanks, were fixed to shatter on impact, throwing water, dirt and debris in the inferno’s path … In all, some 200 modified fuel tanks will be dropped, along with 100-pound chemical bombs, 184 of which fit into a B-29 bomb bay.
In the end, the water bombs never saw action.
We don’t know the exact reason, but we’d hazard to guess that it was inefficient compared to other methods, not to mention the risk of shrapnel from the exploding bombs hitting nearby firefighters. Oh, and environmental threat that is littering America’s forests with hunks of metal.
But military aircraft and tactics continued to play an important role in wildland firefighting. During the 1950s and 1970s, the Forest Service and other agencies converted surplus wartime planes into “water tankers,” still in use today. Rather than dropping bombs, the planes carry internal tanks full of water or flame retardant chemicals.
There’s dangers in simply dumping chemicals, too. The tankers must swoop down at incredibly low altitude. Not only does this put aerodynamic stresses on the aircraft, they must fly close to intense heat … which rises. There’s also inevitable corrosion of the aircraft, since they’re carrying bellies full of liquid.
So the water bomb idea never fully went away. More than a decade ago, Boeing experimented with biodegradable beach balls filled with water that could be dropped en masse from Air Force C-17 transports at far higher altitudes. The little bomblets would burst apart on impact with the ground.
“A single C-17 PAFF mission could airdrop 140,000 pounds of water on multiple “hot spot” targets — equivalent to nearly 100 helicopter deliveries,” the company magazine Frontiers stated.
Either way, this year has been a sobering reminder that fire is a relentless enemy. As one of the worst fire seasons on record burns up wilderness and property in America’s western states, thousands of U.S. troops — many of them pilots and aviation crews — are mobilized to support civilian firefighters and assist threatened communities.