Operation Blowdown was an explosives test carried out in the Kutini-Payamu jungle of Australia's Cape York Peninsula in 1963, to simulate the effects of a nuclear weapon on tropical rainforest.

In addition, blast effects on military material, field fortifications, supply points, and foot and vehicle movement were examined in a rainforest environment.

The final sphere contained a total of 2,438 TNT and 70 CE/TNT booster canisters resting on 408 support blocks with a diameter of approximately 13 feet (4.0 m).

To understand the destructive forces, such an overpressure would correspond to wind speeds greater than 1,000 miles per hour (1,600 km/h),[4] and would be equivalent to a 1.0 megaton blast at 3,000 feet (910 m).

[5] This also helps in understanding how a test of 50 tons could be used to evaluate nuclear weapons which may be in the kiloton and megaton ranges by reducing the distance to ground zero for greater effect.