Getting Serious about the Threat of High Altitude Nuclear Detonations

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Aurora Borealis is the scientific term given to the natural light phenomenon of the Northern Lights. On July 9, 1962, the light phenomenon that Hawaiians watched was anything but natural. On that day, the Atomic Energy Commission, in collaboration with the Defense Atomic Support Agency, detonated a thermonuclear device in low Earth orbit. The test was codenamed Starfish Prime and it revealed an unfortunate lesson: Even one high altitude nuclear detonation is particularly effective at destroying satellites. Not only were satellites in the line of sight destroyed, but even satellites on the other side of Earth were damaged and rendered inoperable. Starfish Prime damaged or destroyed roughly one third of all satellites in low Earth orbit at the time.

The ongoing commercialization of space with cost effective bulk electronics presents a tantalizing target for nations with a space disadvantage to target long-before a conflict could escalate to nuclear exchange. Therefore, the Department of Defense should get serious about planning for and countering the threat of high altitude nuclear detonations, starting with its various science and technology funding organizations.

To do so, the Department of Defense should consider developing a coherent research portfolio with consolidated oversight that aims to maximize the survivability of military and commercial satellites from charged particle radiation. The portfolio should focus on rapidly characterizing the space radiation environment, disseminating this information for satellite countermeasures, vectoring excess charged particles out of orbit, and continuing to subsidize the ongoing commercialization of radiation resilient electronic components.

The threat of nuclear explosions in space is marginalized because the potency of their effects is not widely known and the likelihood of nuclear attack in space is assumed to be negligible. Despite this skepticism, war planners should recognize that the growing number of satellites in space may change the incentive structures to disable them in some sort of nuclear attack. The dynamics of escalation are also not straightforward. The use of a nuclear weapon in space may not invite a nuclear response. This means that the traditional way to deter nuclear use — the threat of catastrophic reprisal — may not be as straight forward as many think. Taken together, there is ample incentive to explore making American infrastructure in space more resilient to this on-going threat.

Lessons Learned from Nuclear Testing

The period from the 1940's through the early 1960's was a bonanza for nuclear testing in every exotic configuration and location imaginable. Approximately 84 percent of the total yield from all nuclear testing was detonated in Earth's atmosphere during this time period. Less well known are the sparse series of nuclear tests that the United States conducted underwater and at high altitudes. Operation Crossroads in 1946 detonated several nuclear weapons underwater to test their efficacy against ships and submarines, but the results revealed that the explosions dispersed radioactive water in the air that rained back down on every vessel with the dispersion area without destroying many ships.

The Starfish Prime test, in contrast, surprised everyone with how effective an exo-atmospheric nuclear explosion was at destroying satellites. Nobel Prize winner Glenn Seaborg, co-discoverer of plutonium and Chairman of the Atomic Energy Commission from 1961 to 1971, wrote that, "To our great surprise and dismay, it developed that Starfish added significantly to the electrons in the Van Allen belts. This result contravened all our predictions." Even more surprising was that the world's first commercial communications satellite, Telstar, was launched the day after the Starfish Prime test and still suffered significant operational damage from residual radiation. Telstar lasted only eight months until it stopped responding in February, 1963 due to damaged electronics. For these reasons along with the concern of increasing environmental radiation, the nations of the world decided that testing nuclear weapons both underwater and in space were bad ideas and banned such activities with the Limited Test Ban Treaty that the United States ratified on Aug. 5, 1963.

Soft Satellites

The Van Allen radiation belts perform a crucial task of sweeping charged particles from the sun away from Earth to create a shield against charged particle radiation from low Earth orbit to the surface (below 1,000 kilometers in altitude). Satellites launched higher than low Earth orbit face a harsher radiation environment and are electronically hardened to withstand the constant bombardment of charged particles. The base electrical units of satellites are typical of all electronics, such as resistors, conductors, diodes, transformers, and memory. In general, these electrical components transfer energy, perform logic operations, and relay information through parts of the electromagnetic spectrum while functioning in near vacuum conditions with a greater radiation background than on Earth.

However, commercial satellites in low Earth orbit take full advantage of the reduced particle radiation and may incorporate standard commercial electronics into their payloads. The use of these components sharply reduces costs. Radiation hardening of electronics is becoming more cost effective and compact, but this practice historically drives the component price up by roughly factors of 10 to 100 while potentially increasing size and mass of the total payload.

Military satellites are substantially more expensive than commercial satellites because they are normally designed to a higher level of electronic hardness, regardless of orbital altitude that increases their resiliency to periods of intense solar activity. The trend in space payload development for low Earth orbit is to launch small satellites, like CubeSats, which utilize low-power microelectronics that operate for only moths to a few years before deorbiting and getting replaced by their upgraded successor. This trend does not mean that small satellites should be thought of as attritable. It is very expensive to haul satellites into space on rockets. CubeSats may be affordable to manufacture but launching them remains costly. Replacement times from fabrication to orbit are at least several months to years, even for small satellites closer to Earth. Thus, the lower manufacturing costs se satellites are not immune from the potential use of high altitude nuclear detonation.

The Department of Defense relies heavily on space to transmit data around the world and uses this data to organize war planning. Take the current war between Russia and Ukraine as an example of the importance of space for war planning. At the outset of the invasion, Russian forces targeted Ukraine's land-based internet and mobile phone infrastructure, greatly reducing Kyiv's ability to maintain effective command and control to the frontlines along with basic informational relay to the populous. Fortuitously, the Starlink project, a developing constellation of small satellites in low Earth orbit delivering high-speed internet access, had the capability to provide internet connectivity to the bulk of Ukraine's forces.

Currently there are over 10,000 Starlink ground terminals in Ukraine, providing internet to over 150,000 people. The Ukrainian armed forces have access to a robust satellite-based internet service that is difficult for Russia to disrupt, absent targeting the satellites themselves. This recent case shows how space assets provide invaluable information products regardless of location.

Nuke Space, Nuke the Economy

To target these satellites, an adversary must have nuclear weapons and long-range missiles. This narrows the list of potential aggressors, but the list includes Russia, China, and North Korea. While the use of nuclear weapons is escalatory, an explosion in space would have a devastating economic impact on the United States. It would also degrade the space-based assets the Department of Defense uses for command and control.

A nuclear explosion in space disproportionately hurts the United States as the largest single investor in space capabilities. The United States nets almost $200 billion per year of real gross output from its space assets. Even though military satellites are designed to withstand a harsher charged particle environment, radiation hardening is not a magic cloak of invincibility. Military space assets will be degraded over time from the artificially amped radiation belt created from the nuclear detonation, meanwhile commercial satellites in low Earth orbit will be the first to fail from continually passing through these particle hot spots. Most satellites with a line of sight to the nuclear detonation will be destroyed from the resulting x-rays. Military space capabilities for command and control along with reconnaissance assets may still function for a period following the detonation, but the economic impact of degraded informational space products will be immediate.

Nuking Satellites is Escalatory, but the Response is not Straightforward

Targeting space with a thermonuclear weapon invites a significant retaliation, but not necessarily a nuclear response. Once an adversarial nation with a disadvantage in space capabilities detonates a nuclear weapon in this domain, there is no benefit to respond with a similar attack. This act would further degrade space-based assets. The use of a ground-based anti-satellite weapon does not have the same effect. It is trading one missile for one satellite, which is not equal to the destruction of a nuclear weapon.

The attacked nation, then, must consider responding with conventional or nuclear weapons on Earth. Targeting cities and military installations with nuclear weapons is not an in-kind response to the initial action of nuking space and represents another significant escalation in the conflict. Space assets are not on par with human lives. Further, the attacking nation will also have nuclear weapons in reserve, and with the right mix of forces can hold targets at risk. Therefore, the attacked nation would have to weigh escalating to nuclear weapons use, knowing that it would invite a nuclear response on targets in the homeland. The obvious response is to signal that the use of nuclear weapons in space would be treated as a nuclear attack on Earth, but an adversarial nation could consider such a threat non-credible.

A nation may also be deterred from acting because every nation in the world is dependent upon space products to some degree. Therefore, using a nuclear weapon in space would be "self-harm." However, as the history of war reveals, nations choose self-harm, such as when they collapse their own bridges and burn fields, to prevent an invader from gaining ground. Nuclear weapons are at the pinnacle of threat escalation, so the use of one is a sign of desperation with diminishing alternative options.

Investing in Mitigation Technologies

Current risk mitigation of the threat of high altitude nuclear detonations myopically focuses on radiation hardening of electronics, which is insufficient, and simply pretending the likelihood of attack is near zero. The Department of Defense should invigorate efforts to counter the threat of high altitude nuclear detonations and recognize that the ongoing commercialization of space will lead to an even greater dependency of low Earth orbiting platforms that will remain vulnerable to the charged particle outputs of nuclear explosions.

The line of utility between military and commercial space payloads will continue to blur. Radiation hardening of all payloads will not be economically feasible unless hardening practices become ubiquitous in commercial components. Recognition of this threat is not novel and should come as no surprise. The Defense Threat Reduction Agency conducted a detailed study of this topic that remains valid today. However, the potpourri of technical programs designed to mitigate the threat to space assets from high altitude nuclear detonations have not been properly funded. The Department of Defense should initiate a concerted research and development portfolio to mitigate this threat by ensuring the greatest number of space assets, both commercial and military, survive a high altitude nuclear detonation rather than just focusing on a few hardened military assets. Assuming an adversary can deliver a nuclear weapon into space uncontested, the following unprovocative focus areas may prove useful in partitioning research efforts.

First, develop radiation sensors that provide rapid assessment of the space environment post-detonation to map out swaths of damaging radiation due to charged particles trapped in the Van Allen belts. Commercial components for space application to characterize high energy electrons, x-rays, and total dose are already available for purchase.

Second, investigate and design a system to relay information from satellite to satellite of the hazardous radiation environment so individual satellites can attempt evasive maneuvers (change of orbit) or simply to enter a low-power mode for a portion of their orbits to improve survivability.

Third, advance satellite systems specifically designed to remove excess charged particles from the Van Allen belts by diverting the particles back into the atmosphere. Such systems are still exploratory but use low frequency radio waves to steer charged particles out of the magnetic field line. By steadily de-energizing amped orbits over time this action prevents prolonged damage to satellites, like the Telstar example, by reducing the total radiation dose.

Finally, the Department of Defense should continue radiation hardening research efforts, but with a focus on advancing hardened commercial components that are economically feasible and ubiquitous replacements to the standard electronics designed for the low radiation levels found on Earth's surface.

The two research and development organizations best suited to champion these efforts with orchestration are the Defense Threat Reduction Agency and the Air Force Research Laboratory due to their existing equities in countering weapons of mass destruction and advancing space systems, respectively. However, the mission of countering high altitude nuclear detonations straddles both thrust areas such that each could look to the other to take lead. Several additional organizations are also capable of leading these developmental efforts, to include the National Nuclear Security Administration and the Defense Advanced Research Projects Agency. The first step to counter this threat is simply assigning a Department of Defense organization to take the lead and initiate the first phase of the program, planning, budget, and execution process.

The possibility of high altitude nuclear weapons targeting space assets is not a novel threat, but one that is historically dismissed. The nature of orbiting around Earth means that space assets are periodically exposed in highly predictable patterns. In fact, delivering a nuclear weapon into low earth orbit is an easier engineering challenge for a nation like North Korea than targeting the continental United States because the missile's warhead has to survive the drag and heat of atmospheric reentry. Space assets are not just tempting targets but become more provocative with each supported military operation. Therefore, the Department of Defense needs to form a coherent research and development plan with a dedicated lead to champion the mission of countering high altitude nuclear detonations.

Lt. Col. "Tony" Vincent is an active duty scientist in the United States Air Force and is currently the Director of Advanced Physics Courses at the Air Force Academy. He received a Doctorate of Philosophy in Atmospheric Physics from the University of Oxford, a Master's of Military Operational Art and Science from the Air Command and Staff College, and a Master's of Applied Physics from the Air Force Institute of Technology. Lt. Col. Vincent was also a Nuclear Threats Program Manager at the Defense Threat Reduction Agency and the optics lead for the third deployment team with project AngelFire in Operation Iraqi Freedom. The views here are those of the author and do not represent those of U.S. Air Force, the U.S. Department of Defense, or any part of the U.S. government.

Image: Nuclear Weapon Archive