World’s Outer Space Treaty Came 55 Years Ago

First and largest nuclear detonation in space played a role

Tim Gebhart
7 min readJan 23, 2022


An aerial view of the aurora created by the Starfish Prime nuclear test (Los Alamos National Laboratory)

OnOn November 15, Russia fired an anti-satellite missile at one of its old satellites. When hit, the satellite shattered into hundreds of thousands of pieces, of which only 1,500 or so are trackable. The only international treaty governing humanity’s activities in outer space turns 55 this month. It was sparked in part by the first test of a nuclear weapon in space.

The Starfish Prime Nuclear Test

From 1951 through 1966, the US conducted more than 475 nuclear weapons tests. During the same period, the Soviet Union conducted more than 250 tests. In 1962 alone, they conducted 174, more than twice the annual average during the Cold War. One US test, called Starfish Prime, drew worldwide attention — and condemnation — because it was not only the first nuclear detonation in space but also the largest.

Around 11 pm local time on July 8, 1962, (July 9 in the continental US), the US launched a Thor rocket from Johnston Atoll, about 900 miles west-southwest of Hawaii. It reached some 660 miles and when it descended to 250 miles just more than 13 minutes after launch, a 1.4-megaton hydrogen bomb exploded above the Pacific Ocean. (Outer space is commonly defined to begin 62 miles above the Earth.) The warhead was 100 times more powerful than the atomic bomb dropped on Hiroshima 17 years before.

The explosion produced a dramatic light show. According to a 1983 report by the Defense Nuclear Agency, the energy it released “caused widespread auroras” throughout the Pacific, some lasting up to 15 15 minutes. They were seen on both sides of the equator. “In Honolulu,” the report says, “an overcast, nighttime sky turned into day for about 6 minutes.” Almost as an aside, the description concluded with, “The Earth’s geomagnetic field also was observed to respond to the burst.”

That was an understatement as scientists were surprised by the effects. For example, according to a 2000 report on anti-satellite weapons by the US Air Force Academy:

The test produced a visual extravaganza as well as several unintended effects that reverberated in Washington. The nuclear blast knocked out electrical systems…



Tim Gebhart

Retired Lawyer. Book Addict. History Buff. Lifelong South Dakotan. Blog: