‘Huron King’ test on 24 June 1980: Exposing a satellite to an EMP blast

The Tinderbox - test chamber

24 June 1980 - Huron King

Telstar was not only the first commercial communication satellite ever, also one of the first to be damaged by an outer space nuclear explosion.

On 24 June 1980, the United States conducted the underground ‘Huron King’ nuclear test as part of ‘Operation Tinderbox’. This operation consisted of a series of 14 nuclear tests conducted in 1979-1980 at the Yucca Flats test range, which is part of the former Nevada Test Site. This unusual series of tests was aimed at ensuring that military satellites would be tough enough to withstand a nuclear Electromagnetic Pulse (EMP) attack.

Both the United States and the Soviet Union had conducted a limited number nuclear tests aimed at testing the effects of nuclear weapons in high altitudes/lower outer space. One of these was the ‘Starfish Prime’ test of 9 July 1962, which was later found to have damaged and disabled many of the early satellites in orbit at the time, including Telstar, the first commercial communications satellite.

By the 1970s, scientists had developed technologies capable of ‘hardening’ satellites from the effects of EMP, but with the Partial Test Ban Treaty (PTBT) coming into effect on 10 October 1963, it was prohibited to conduct nuclear weapons tests anywhere except underground. Thus the need to find a way to use an underground nuclear explosion to test whether the satellites’ new shielding worked.

They actually put missile warheads, satellites, et cetera in to see what the effects would be if there was a detonation nearby (…) in space, and to harden the warheads from the enemy shooting off missiles, trying to in any way make them ineffective.Joan McCarthy, junior laboratory technician at the Nevada Test Site
The Tinderbox - test chamber

The result was the Huron King test and its ‘Tinderbox’, a giant 50-ton vacuum chamber on tractor treads large enough to hold a military communications satellite. Under the Tinderbox, a 1,000-foot (around 300 metres) deep pipe was drilled into the ground that ran straight from the chamber where the satellite was suspended to the nuclear bomb at the bottom of the pipe.

Huron King was unique in that it was a VLOS [vertical line of sight] underground nuclear test, as opposed to the more common Horizontal Line of Site test, with a yield of less than 20 kilotons.U.S. Department of Energy National Nuclear Security Administration, Nevada Field Office
Huron King aerial view before the test

When the bomb detonated with a power of less than 20 kilotons, the satellite was exposed to the electromagnetic pulse for a fraction of a second through the pipe. After this, mechanical closures immediately sealed the pipe to prevent the shockwave accompanying the explosion from reaching the satellite. The test chamber was then disconnected from the pipe within seconds and moved back from ground zero to safety, before the ground subsided into a crater.

An inspection of the satellite after the test showed that the EMP shielding had worked as intended. The Huron King test chamber was never used again and can still be seen at the former Nevada Test Site.