Remember When Australia Pretend-Nuked a Rainforest?

Operation Blowdown tested atomic effects on the Australian jungle

Remember When Australia Pretend-Nuked a Rainforest? Remember When Australia Pretend-Nuked a Rainforest?

WIB history September 10, 2018

This story originally appeared on Aug. 22, 2015. During the Cold War, nuclear states tested atomic weapons in almost every conceivable environment — deserts,... Remember When Australia Pretend-Nuked a Rainforest?

This story originally appeared on Aug. 22, 2015.

During the Cold War, nuclear states tested atomic weapons in almost every conceivable environment — deserts, oceans, space, islands. Scientist already knew nukes’ effects on cities. But how would they affect jungles?

The Australian government wanted to know. So in July 1963 Australia conducted a simulated nuclear test in order to find out.

The administration of Prime Minister Robert Menzies had looked north and saw trouble brewing. The previous decade had witnessed a brutal guerrilla campaign in Malaya and unrest in Indonesia. Communist insurgencies roiled Laos and South Vietnam. Mao Zedong’s China, not yet a nuclear power, loomed over the region.

As in World War II and the Korean War, the Aussies expected they’d wind up fighting with the Americans in Vietnam. If the United States jumped in with both feet, it just might use nukes.

Australia already had experience with The Bomb. In the 1950s, the country had hosted several British nuclear tests that contaminated lots of land and hurt a lot of people. The tests’ impacts remained classified until the end of the 20th century and, when revealed, caused serious tensions between the United Kingdom and its former colony.

Perhaps with those secret side-effects in mind, the Menzies government was reluctant to explode a real nuke in the ’63 test. Although atmospheric tests were legal then — the Partial Test Ban Treaty was signed a week after the blast — test planners chose conventional high explosives to simulate a low-altitude, 10-kiloton nuclear airburst.

Doing so required 51 tons of TNT.

The Australian army and the Department of Supply invited defense researchers from the United States, the United Kingdom and Canada to join the preparations and to observe the test in exchange for data. America provided advanced electronic measuring equipment and experts in nuclear blast effects. Some of the equipment the United States supplied had previously been used in connection with the Project Plowshare nuclear tests in Nevada.

Preparations for Operation Blowdown began with test workers cutting a path into the virgin rainforest and erecting a 156-foot-high steel tower. Atop the tower, workers very carefully stacked cubic cans of TNT into a 13-foot-diameter sphere. The tightly packed cans left no gaps to disturb the blast’s propagation.

The TNT came from expired 155-millimeter artillery shells, which testers extracted, melted and poured into the cans.

Given its name, it’s not surprising that Operation Blowdown focused primarily on how well a nuke could blow down a forest. To quantify that, researchers measured more than 17,000 trees near Ground Zero before the test, from saplings to jungle giants. After the explosion, they compared their measurements with what remained in order to gauge the bomb’s effects.

In addition to effects on forest cover and troop movements, defense scientists wanted data on hardware. Around the tower in the jungle below, test workers built simulated fortifications, set up communications lines and radios, stood up uniformed dummies and parked obsolete military vehicles.

On July 18, 1963 the hundreds of workers, soldiers and scientists at the Iron Range test site retreated to safe distances and meteorologists assessed the weather. With all signs good and the vast array of instruments and recorders running, the 51-ton bomb exploded with ripping force, instantly crushing the water out of the air and turning 100-foot-high eucalyptus to kindling. Thirty-seven acres of jungle became a matchstick pile of trunks and debris.

So how useful is a tactical nuke in the jungle? Well, less so than expected. Despite a lot of damage well-led sapper teams armed with machetes and axes still managed to chop their way through the flattened forest patch. Simulated combat patrols found their movements impeded but not stopped by debris.

A U.S. Army observer noted that the tree trunks and fallen vines offered cover to attackers and defenders. Both sides had to expose themselves to fire while clambering around the mess. Though platoon leaders enjoyed greater visibility for reconnaissance and command signals, they faced greater exposure. “It was obvious,” the officer wrote, “that the requirement for adequate covering fire would be of prime concern in the post-test operation.”

Apparently there were no attempts to simulate fallout or radiation effects, which would have made crawling around a woodpile much less pleasant.

The blast damaged the fortifications and vehicles, but not fatally. Machine-gun barrels bent, a mortar was thrown from its emplacement and a 25-pound gun sustained “some damage.” Radio masts and communications cables were hardly affected. Some supply caches broke open when struck by flying debris.

Since scientists previously knew so little about nuclear-weapons effects on tropical forests, those involved considered Operation Blowdown a success. The test demonstrated the limits of tactical nukes as barrier-creators in jungle environments. Three years later those limits resurfaced in a classified study on the potential use of tactical nukes in Vietnam.

Nukes, it turns out, just aren’t very useful in the jungle, unless you want to get rid of the jungle. Fifty years later, those 37 acres of flattened forest have never grown back.

One thing did grow out of Operation Blowdown. A decade before a U.S. nuclear test in Alaska galvanized the environmental movement, the Queensland test appalled Australians with the damage it inflicted on the rainforest. Australia conducted no more such tests.

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