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If you have been following the news lately, you might have seen some rather alarming headlines like, “Russia Could Put a Nuclear Weapon Into Orbit This Year” [1] or “US Tells Allies Russia May Launch Anti-Satellite Nuclear Weapon Into Space This Year” [2]. While APELC is certainly in no place to comment on the credibility of these threats, we do have some expertise in the phenomena behind them—specifically, high-altitude nuclear EMP (HEMP) events. As we have mentioned in previous blog entries (see: INCREASED EMP THREATS AND TESTING STANDARDS PART 1: UNDERSTANDING THE THREAT), an HEMP is generated by a high-altitude nuclear burst interacting with the upper layers of the Earth’s atmosphere as well as the geomagnetic field.

One of the most well-documented HEMP events, known as “Starfish Prime”, occurred in 1962 above the mid-Pacific Ocean at an altitude of 400km above the surface of the Earth. By comparison, low-Earth orbit (LEO) is defined by NASA as 2000km above the Earth’s surface. If Russia is looking to launch a nuclear device into space as a means of disabling or destroying US satellites, we can assume that it would need to reach somewhere near this altitude to have the intended effect. Because APELC is much less familiar with the types of interactions that would occur at this altitude, we reached out to a colleague for some insight into this potential threat. Wallace T.“Wally” Clark III is presently a consultant for the National Nuclear Security Agency (NNSA) on nuclear explosives safety, a Senior Fellow of the National Institute for Deterrence Studies (NIDS:, and retired from his previous role as the Deputy Chief Scientist for the Air Force Nuclear Weapons Center. Dr. Clark was kind enough to give us some of his time and thoughts on the matter. Below is an excerpt from an email exchange with Dr. Clark:

In an atmosphere there are seven basic nuclear effects: Blast, Overpressure, Shock, Thermal, Electromagnetics, Radiation, and Dust. These effects can be easily remembered using the acronym BOSTERD. Several of these have sub-categories and several also have sub-sub-categories. Which of these effects would also “exist” in a space environment?

  • Blast: In the heart of a nuclear detonation pressures reach thousands of atmospheres but without an atmospheric medium to transmit this pressure there will be no blast effect unless the detonation is located within a very few meters of the target.
  • Overpressure and shock: Both depend on an atmosphere, so this is of little concern here.
  • Thermal: In the heart of a nuclear detonation temperatures can be in excess of one million degrees, but without an atmosphere, the heat will be localized.
  • Electromagnetics: EM effects will not be a localized phenomenon.

Electromagnetic Pulse (EMP)

EMP effects occur within a straight line-of-sight of the detonation. In an atmosphere nuclear EMP is generated by the detonation’s emitted gamma particles ionizing the oxygen and nitrogen molecules in the atmosphere, thus generating free electrons, which produce a burst of EMP energy .

System Generated EMP, or SGEMP, is of concern in a space environment. SGEMP refers to the electric field that can be generated by the interaction of gamma particles and X-rays with various solid materials present in and surrounding electronic systems, like satellites. The gammas and X-rays interact with the materials enclosing satellite electronics. SGEMP is generated within the enclosures and on the electronic components.

SGEMP is also called IEMP or Internal EMP. Consider a system designed to shield from the ravages of EMP. The electronics are placed within a metal case, possibly an EM signal-blocking Faraday Cage. Yet, gammas and X-rays striking the case, the electronics, and any material within the case produce electrons that interact with other solid materials to release yet more secondary electrons. So, an electric field is generated near the surfaces. In space or at high altitudes, the electric field on the interior walls can reach 100,000 to a million volts per meter. Large currents and voltages, capable of causing damage or disruption, can be developed just as with external EMP.

ECEMP is Electron Charging EMP, and it’s similar to SGEMP. Orbiting satellites are constantly exposed to the natural space plasma and charged particle environment. With sufficient charging, say from orbiting through a radioactive debris dust cloud, an electrical discharge can occur between different portions of the satellite which creates an electromagnetic transient that can couple into satellite electronics.

DEMP, or Dispersed EMP is the space bound EMP formed from a HEMP explosion where a satellite or other system passes through the far upper ionized atmosphere, collecting charge that can lead to an electrostatic discharge. DEMP is similar to electron charging ECEMP.Radiation: A non-localized phenomenon.

Radiation: Both the Soviet Project K and the U.S. Starfish Prime high-altitude detonations produced artificial radiation belts in space that soon destroyed satellites after the satellites traversed the belts

Dust: Another non-localized phenomenon.

Dust, in the form of weapon debris, is likely radioactive and may scour the exterior of satellites.

The seven BOSTERD effects in an atmosphere are reduced to three in space, but those three would wreak havoc on satellites, destroying and degrading their functionality. Four final points to consider:

  1. A nuclear detonation in space will not be a localized or an aimable effect. The aggressor will harm the adversary but quite likely himself as well.
  2. Compared to conventional explosives, nuclear is probably quite expensive.
  3. I suspect that the goal of placing a nuclear weapon in space is not limited to the Russians; don’t discount North Korea, China, or Iran.
  4. Even if a power does place a nuclear weapon in space they must account for the U.S. deterrence policy of Ability to retaliate, Resolve to retaliate, and an adversary’s knowledge and understanding of that ability and resolve.

If you would like to hear more of Dr. Clark’s thoughts on Nuclear Weapons Effects, you can find several podcasts he recorded at




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