Nuclear Weapons: what you need to know

After thirty years in hiding, the possibility of nuclear war is back in the news. You’re hearing about Russian threats and the Chinese build-up, while minimizing our own problematic actions such as the W76-2 program. Over the last 30 years there has been an under-the-table arms race while at the same time the arms control framework of the late Cold War has been abandoned. I’ve done another podcast with Nate Hagens you can find here, this time discussing in more detail why nuclear weapons are so dangerous, and most importantly what we can start to do about it. This post is an introduction to the subject and preview of that discussion.

I worry that the general public (and many of our political leaders) seem to have lost touch with just how different nukes are from conventional bombs. The days of “duck and cover” exercises in schools are long gone (even before my time!), and if you’re much under 50 you never saw movies like War Games or The Day After, or recall the scares when President Reagan joked about bombing the Soviet Union (or know why that rhetoric was suddenly toned down). I would also guess that there is “doom fatigue,” between COVID and Climate Change, as well as the constant drumbeat of disaster news of various kinds. Nuclear war seemed, until the Ukraine SMO/invasion, a problem of the past. Another factor is complexity. The topic of nuclear weapons can’t be separated from a discussion of doctrine – how these weapons fit into our war plans and their intended use, and involves a topic many Americans don’t know much about and mostly don’t seem to care: foreign policy. So this is a difficult-to-understand interplay of physics, military strategy and tactics, politics, international relations, and of course morality and ethics. And like most complex subjects, the news media, increasingly fueled by social media, oversimplifies, dramatizes, and politicizes stories to “engage and enrage” viewers. So concise information is hard to find.

What follows is a bit of an introduction to this horrible topic. I’m sure subject area experts will find simplifications and interpretations to disagree with, and of course this area is obscured with security aspects that are often used to hide issues that should in fact be publicly disclosed and debated, like doctrine. But here’s a “short” 😛 introduction from my point of view.

For perspective let’s start by looking at the largest conventional bomb routinely dropped from aircraft by the US in combat. That is the GBU-31, which is a 2000 pound bomb that weighs about 2036 pounds. Conventional bombs are destructive primarily through the blast wave and fragmentation. The blast radius (defined as significant structure damage) of the GBU-31 is about 60 meters (66 yards – a meter is about 10% longer than a yard), but fragmentation means the bomb is often deadly to unprotected people at 350 meters. Put another way, a GBU-31 basically wrecks a high school football stadium sized area.

Nuclear weapons are so powerful that we needed a new language to discuss them. Rather than pounds of explosive, we normally use thousands of tons of TNT equivalent. The GBU-31 on that scale is about a 1 ton explosive, or 0.001 kilotons. The largest conventional combat bomb used by the US is the GBU-43 “Massive Ordinance Air Burst” or MOAB. It has only been used once, in Afghanistan, against the Tora Bora tunnel complex. The GBU-43 bomb itself weighs about 21,600 pounds, has an explosive force of about 11 tons (0.011kt) of TNT, and a blast radius of about 150 meters, although it can cause severe injury at much greater distances. About the scale of wrecking a pro football team stadium and parking lot. You’ll notice that although the GBU-43 is 10 times larger than the GBU-31, the blast radius is only twice as big. I’ll spare you the math, but all things being equal to double the blast effects takes about eight times the energy.

Most people think of nukes in terms of wrecking entire cities (continuing with our football stadium analogy). But it’s not so simple. Before examining the raw explosive force of a nuke, we need to explore another difference between nuclear weapons and conventional bombs. A key feature of modern nuclear weapons is they are not limited to one fixed explosive force (the “yield” of the bomb). Modern nuclear weapons are known as boosted devices. In basic terms, the yield of a nuclear bomb is a race between the nuclear reactions in the bomb releasing energy, and the bomb blowing itself apart, stopping the reaction. Typically only a fraction of the material in a fission bomb is utilized in a nuclear weapon, thus releasing energy. The bomb dropped on Hiroshima only consumed about 1.4% of its nuclear fuel. Adding tritium and deuterium gas into the core of the bomb – known as boosting – has enabled amazing improvements in the size and efficiency of nuclear weapons. It also allows the yield of the bomb to be controlled by adding different amounts of gas to the core before detonation. While this variable yield has operational military advantages, as will be discussed it is also a considerable danger with respect to doctrine and how an adversary might respond.

The primary aircraft delivered nuclear bomb in the active US arsenal is the B61. It has over a dozen configurations (“mods”) and a confusing array of potential yields. The mod 7 has a yield ranging from 10,000 to 360,000 tons of TNT, while the mod 3 and soon to be deployed upgraded mod 12 has a selective yield ranging from 300 tons to 50,000 tons of TNT. At the smallest setting of 300 tons or 0.3 kilotons, the blast radius is about 320 meters. At the highest, the blast radius is over 6,000 meters. Compare this with the GBU-31’s blast radius of only 60 meters. These maps compare the impact of the GBU-31 with various nuclear weapons, using an aim point of Columbus Circle at the southwest corner of Central Park in New York City. The first map is zoomed in a bit to see the smaller areas …

And here is the full view showing the larger weapon blast radii:

Another consideration with nuclear weapons is that the blast wave isn’t the only source of destruction. A conventional bomb releases most of its energy in the form of the blast wave. Nuclear bombs release 50 per cent energy as blast, 35 per cent as thermal radiation or heat, and 15 per cent as nuclear radiation and EMP. Thermal radiation is essentially heat, and can trigger fires and cause severe burns to unprotected people well beyond the blast radius. Combined with the blast wave (which damages buildings and creates tons of flammable debris, then “blows on the fire” with wind), the thermal radiation triggers huge firestorms after the blast. The firestorms represent a considerable element in the destruction wrought by a nuclear bomb.

What most people think of as nuclear radiation is ionizing radiation cause by subatomic particles (technically both the thermal radiation and EMP are also “radiation” as well). Prompt radiation is the nuclear radiation generated by the nuclear reactions in the blast, and can extend beyond the blast radius at lower yields. Using the 0.3kt setting on the B61-3, the blast radius is 300 meters, but radiation is deadly at double that range (600 meters). One of the weapons discussed in the 1980’s was the so-called “neutron bomb” (more correctly an enhanced radiation weapon). It was one of several designs that were created around the concept that by minimizing blast and maximizing radiation, you could kill people but not be as destructive of property. The US began production of one (the W70), but it was controversial to say the least, fed the growing anti-nuclear movement, and the outcry in Europe was so intense it was never deployed there and on paper withdrawn from production. However, the B61 in low yield modes is almost the same in impact, and these are now stockpiled at European bases. The German Green Party was instrumental in those protests – yet current German Foreign Minister Baerbock, who was only three years old at the time of the Neutron Bomb and Pershing Missile controversies, is actually supporting the ongoing B61 upgrade and deployment. I wonder what her parents, who were active in those protests, think. This is a dramatic example of how nuclear weapons have both dropped out of public awareness and been politically normalized.

Delayed radiation is contained in the fallout from irradiated debris that are swept up in the blast as well as debris from bomb itself. This can be deadly at long distances – hundreds of miles, even farther is some cases – from the explosion site if carried by the wind, and have effects many decades after the blast. The Chernobyl reactor meltdown created radioactive hot spots across Europe that are problematic even 40 years later.

Another factor is the electromagnetic pulse (EMP) from a bomb, which can overload and destroy electrical systems hundreds of miles away from the blast and is a potentially major “secondary” effect from nuclear weapons. A single explosion in space can damage satellites around the entire planet due to high energy particles being trapped by the earth’s magnetic field. Both the US and Russia (and presumably China) have plans to do just that to disrupt GPS navigation and spy satellites in case of war. Some weapons are designed to be deployed in such a way as to enhance EMP.

By adjusting the height of the detonation, you can dramatically change the impacts on the ground. The detonation altitude depends on the target to be attacked. If the target is “hardened” like a missile silo or underground command center, you might set the detonation point as the surface (or even under it – some weapons are designed to penetrate the ground or concrete before going off). In this case, the fireball (which is on the order of 3000 C or over 5400 degrees F) will vaporize anything nearby, ensuring destruction. A key disadvantage of this is that a “surface burst” creates enormous amounts of radioactive debris to be scattered far downwind, as well as lifted into the stratosphere which can cause global impacts. If the objective is to maximize damage, you might set the altitude so as to optimize the radius of 5psi overpressure (the pressure at which most buildings collapse). In that case, for large yields, the fireball and most deadly “prompt radiation” effects might not even reach the surface! Likewise, if the objective is to kill the people in the target area but cause less damage, a low yield/high radiation configuration might be used, set to detonate above the ground.

So, again, nuclear weapons use is far more complex than conventional systems, and the potential impacts on the environment hard to predict without knowing how the device will be employed. While doctrine (the philosophy and plans behind the use of a weapon system or force) is always important, it is especially critical when discussing nuclear weapons.

With nuclear weapons there is often a distinction made between “tactical” and “strategic.” This terminology can be confusing because it means different things in different contexts. Sometimes it is used as a proxy for yields, with 50kt or less considered “tactical” and over that “strategic”. Sometimes the terms are used in arms control treaties based on the range of the delivery systems or other characteristics. And in military terms tactical, operational, and strategic are “terms of art” that refer to the scope of an operation. “Tactical” means battlefield use in support of specific military objectives and operations, whereas “Strategic” generally refers to objectives that are of importance to the overall warfighting ability or political/governmental structures but are not tied to a specific operation. For example, destroying a port would be strategic in the sense of limiting the ability of an enemy to move supplies or conduct commerce. The same strike might be considered tactical if you were doing it limit the ability of an enemy to resupply an ongoing battle. So even here the lines are blurry.

One reasonably clear “strategic” use of a nuclear weapon would be to destroy a city. Note that bombing a city just for the sake of destroying it and killing people is illegal under international law and a war crime. Such attacks are often justified (as in World War II) as attacking the industrial capacity of the country, but everyone pretty much knows that is just an excuse, and the actual goal is to create political pressure to end the conflict and demoralize the enemy. If it gets to that point such legalities are unlikely to matter.

Although I try to be careful, I find myself unconsciously jumping from meaning to meaning depending on if the context is military or diplomatic, often without being clear about what is meant, and other analysts frequently do the same. Pavel Podvig, an analyst of Russian nuclear systems based in Geneva and one of the best public voices in the field, has a good twitter thread discussing this. His first point needs emphasis: A “Nuclear weapon is a nuclear weapon. It’s not the yield or the range of the delivery vehicle that counts. It’s the mission.” He later points out that any use of a nuclear weapon (and I would add especially a first use) is strategic in the sense that, as noted above, nuclear weapons are different for many reasons and represent a significant escalation and change in the nature of war. Given their destructive power and inevitable civilian impacts, they are inherently a moral and ethical line that is even greater in import than the decision to go to war itself.

Contrary to what Podvig is saying, I think some delivery systems such as land based Intercontinental Ballistic Missiles (ICBM) or submarine launched ballistic missiles (SLBM) are inherently strategic, while others are clearly geared more towards battlefield use. He is correct that technology and other trends are blurring that line. In my opinion this is perhaps the most dangerous and destablizing current trend. The decreasing practical differences between a submarine launched cruise or hypersonic missiles and SLBM is making that line less distinct, complicating treaty language, and making the world more dangerous. More precise targeting is good in that it means a given mission can be completed with lower yields; but that also means there is less warning and a greater temptation to resort to a nuclear attack.

I also disagree with Podvig (and more significantly so does the US Army Training and Doctrine Command) when he says “To achieve a militarily significant result you would have to use a lot of weapons against a lot of targets.” Once even a single a nuclear weapon is used and the “nuclear threshold” is crossed it changes the entire face of the battlefield. Tactics in both offense and defense must adapt to the potential threat. In a conventional war, you try to concentrate your forces to break through enemy defenses – something extremely difficult in a nuclear context as any concentration of forces becomes a lucrative target for a nuclear strike. Likewise, fixed defensive formations become much more dangerous as they too become targets. Another use of nuclear weapons is to block off lines of movement – the destruction, debris, and contamination makes movement through an area hit by a nuclear weapon difficult. There was extensive discussion of these tactical aspects and issues during the cold war. For a deeper dive in to this you can read this 1980 Army Staff College study: Tactical Nuclear Operations: the Doctrinal Dilemma or dig in to US Army Field Manual 100-30.

The big fear during the Cold War was that any attempt to use a nuclear weapon on the battlefield (ie “tactical” use) would almost inevitably lead to “strategic” use. The problem with many modern weapon systems is that they are potentially making battlefield use more tempting, therefore starting the “escalation spiral.” Nate and I discuss this a bit in the podcast. At some point in a war one side or the other has to be willing to give up, or be forced to do so. With a strategic arsenal, another option is added: make sure both sides lose. While this is a deterrent before war starts, it becomes an existential risk once the bombs start flying. But that’s a topic for another post …

So it is vital to keep in mind that nuclear weapons are not just big radioactive explosions. They have secondary effects well beyond just the explosive force and prompt radiation. The operational characteristics (like selective yields) and plans to use them (doctrine) makes some kinds of nuclear weapons and their delivery systems inherently destabilizing. This is a danger we’ve ignored for the last 30 years, while the technology and doctrine has changed significantly over that time. The framework of treaties and lines of communications that existed at the end of the Cold War has fallen apart, and for all of those reasons the danger of nuclear war has probably never been greater. We need to quickly re-establish safeguards and step away from the brink. The future of humanity – and most other life on earth – literally depends on it.

3 thoughts on “Nuclear Weapons: what you need to know

  1. Thanks for the analysis. Just when I think that maybe saner heads (only in Russia) might prevail vis-a-vis Ukraine, you bring me back to the reality that we are in a dire predicament. One can only hope that no one uses any tactical nukes, because it would appear that an escalation spiral is almost guaranteed.

  2. I have the feeling that within all of the countries with nuclear weapons, there is a General Buck Turgidson character pushing for the use of these weapons. Global Thermonuclear War may unfortunately be inevitable. I guess it is either that or a climate catastrophe.

  3. I appreciate the deep dive you provide which can be attained nowhere else…you always change my thinking chuck

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