Finding Nukes on the Final Frontier?
Doc, I saw an article in my feed to the effect that scientists can use cosmic rays to figure out if other countries are putting nuclear weapons in space (did I get that part right?). How does that work? And does it work?
I hadn’t heard of this one, so thanks for the opportunity to learn something new! Turns out there’s also a somewhat longer piece in Scientific American, and a link to the original paper, published in the respected journal Nature. Here’s what I was able to get from these pieces.
We need to start with the Outer Space Treaty of 1967, which flatly states that weapons of mass destruction – and specifically nuclear weapons – can’t be lofted into space or placed on any celestial body. The problem is that there’s no neutral organization to check payloads before a satellite goes up, nor to check any of what’s already in orbit – it’s all on the honor system. Which is OK as long as you trust the other guys; the problem is that we’re not quite sure how far they can be trusted, and it’d be nice to have a way to check on some of the satellites that are already up there. That’s why this work by nuclear scientist Areg Danagoulian is so intriguing.
One question, of course, is why any nation would want to put nuclear weapons in orbit. It doesn’t make much sense from the standpoint of launching a surprise attack on a rival; attacking a foe using an orbital weapon might be a little faster than launching one from halfway around the world, but submarine-launched missiles can reach their targets pretty quickly without breaking any treaties. On the other hand, the US and other nations have thousands of satellites in Earth orbit and setting off a nuclear weapon could knock many of these out of service. That could interfere with navigation and precision-guided munitions (by taking out some or all of our GPS satellites), information and battle management (by taking our satellite internet capabilities), and communications (by disabling or destroying communications satellites) – affecting not only American war-fighting capabilities, but the US economy as well.
This concern is more than hypothetical, by the way; it was first noted in a test detonation set off on July 9, 1962, during the Starfish Prime high-altitude nuclear test; a 1.4 MT thermonuclear weapon that was detonated at an altitude of 250 miles. There were only a few satellites in orbit at that time, but the electromagnetic pulse damaged two communications satellites and affected the Hawaiian electrical grid and disabled a telephone microwave relay station along with other adverse effects; since then our reliance on today’s far more numerous satellite fleets has grown tremendously. The bottom line is that keeping nuclear weapons on the surface of our planet is a good idea.
A few decades ago I’d first heard of using a type of cosmic ray called a muon for probing cargo containers for nuclear materials; muons are deflected by material they pass through and the higher the atomic number, the greater the scattering angle. So the uranium or plutonium in a nuclear weapon, for example, would scatter muons through a larger angle than the iron and aluminum of, say, a crate of auto parts. When I read this article’s title, then, I assumed they were going to talk about muons. The only problem is that muons are created when incoming cosmic rays slam into atoms in the atmosphere; in orbit there’s effectively no atmosphere and not much of a muon flux. Which had me scratching my head a little, until I read further. Turns out there are other particles that can be used to look for uranium and plutonium – particles that are present in abundance in Earth’s radiation belts.
The space near Earth is lousy with high-energy protons, and when protons encounter heavy atoms, they can produce spallation neutrons when they knock neutrons out of the nucleus. Most spacecraft are made of light atoms but, if a nuclear weapon is present the uranium or plutonium will spall, producing neutrons. So there are normally neutrons in space, but typically in low numbers; elevated neutron levels in the vicinity of a suspect satellite could indicate the presence of a nuclear weapon. Easy-peasy! In theory. Oh – and did I mention that the radiation detectors in the proposed satellite include a couple of layers of diamond?
The problem is that the number of “extra” neutrons is relatively low and “seeing” enough of them to give a high probability of making a correct assessment requires spending several days – perhaps as long as a week – in relatively close proximity (a few kilometers or closer) to the target satellite. And this could raise suspicions and cause tension with whichever nation, friend or foe, put it into orbit. So, as it stands now, this technology is a good start, but it’s not yet practical.