You Might Want to Know: How accurate are our guided missiles? Part One
You Might Want to Know: How accurate are our guided missiles?
Part I
We’d like to believe our bombs and missiles will always hit their targets. Almost always. Or most of the time, anyway.
We’d like anyone who is thinking of picking a fight with us to believe this too. But it might be wishful thinking. We might have gotten the idea that our bombs and missiles are more accurate than they are.
After the end of World War II, our Strategic Bombing Survey revealed that more than 60% of the bombs dropped from airplanes in our “precision bombing” missions missed their targets, often by quite a lot. If you dropped a lot of them, your odds hitting your target would of course improve. You just had to hope that the ones that didn’t hit the target wouldn’t hit something you didn’t want to hit.
The inaccuracy of our “precision bombing” was why in March 1945 General Curtis LeMay started to fire-bomb Japan. In fire-bombing, the target is just an area, whatever and whoever is there, not anything more specific. You hope to kill everybody in the area. Soldiers can’t do that. It would be a war crime.
The atomic bombs we dropped that August did area bombing. Atomic bombs are so big they can’t not do area bombing. The bombardiers did have aim points for their single bombs but it wasn’t that important that they hit it. There was some talk about bombing military facilities and factories in those cities, but the target was the cities. It couldn’t be otherwise. Maybe some people didn’t realize that at the time, or even now.
In 1946, in our first nuclear test in the Pacific after World War II, a Nagasaki-type bomb was dropped by a bomber. On a clear day, with no one shooting at it, the bomber missed its target at Bikini atoll by half a mile.
The measure of accuracy our Air Force chose to use for our missiles was the one used by the Army’s artillery—the Circular Error Probable. The CEP is the radius of the circle in which the missile’s warhead, or the artillery round, can be expected to come down, half the time anyway. You can see that we don’t expect perfection, not even with artillery. Maybe our military didn’t mind if we in the public or our enemies had different expectations. In any case, when we came up with the CEP for a missile, whether it was a big area or a small one, we weren’t going to share the information with just anyone.
Our first missiles weren’t “guided.” They were “aimed,” like artillery rounds. We pointed them where we wanted to them to go. After artillery rounds shoot out of the tube, they are affected by gravity, of course, and also by wind and air temperature. The soldiers would try to allow for all these things. But the farther the unguided rounds have to travel, the less accurate you could expect them to be.
Missiles are affected by the same things that affect artillery rounds, but they travel much, much farther.
The first missile we developed that could carry a nuclear warhead was the Honest John, first tested in 1951 and deployed in Europe with our army in 1953. It was an unguided missile with a range of something over fifteen miles. It wasn’t even as accurate as an artillery round, but its W7 warhead would yield twenty kilotons, one Nagasaki, more than a thousand times what we might expect from an artillery round. That lack of accuracy might not matter much.
If you can figure out how to make a missile “guided,” its path can be altered after launch. This might allow for greater accuracy.
Our first Intercontinental Ballistic Missile, the Atlas, came into service in 1960. As an ICBM, it was aimed at targets in the Soviet Union that were over six thousand miles away. It would be guided by radio signals--for as long as we could get radio signals to it anyway.
For later versions of the Atlas, we developed “inertial guidance systems.” These were devices inside the missile that used gyroscopes to correct deviations from the intended paths. Since these guidance systems were inside the missile, they couldn’t be interfered with the way radio signals could be. Also they’d be able to communicate with the missile all the way there.
Our Air Force estimated the inertial guidance systems would give the Atlas ICBM, after a flight of over six-thousand miles, a CEP of 3.7 kilometers, about three miles. The warhead for the Atlas, the W49, had a yield of 1.44 megatons, a hundred Hiroshimas. The 100% fatality radius for the W49 was only a little less than its CEP.
Our second ICBM, the Titan I, still used a radio system. But the Titan II that we got not long afterwards used a newer inertial guidance system that gave it a CEP of about a thousand meters, less than a mile. Its warhead, the W53, had a yield of nine megatons. The radius of the 100% kill zone of the Titan II’s nine megaton warhead could approach four and a half miles, more than four times its CEP.
Our first solid-fueled ICBM, the Minuteman, deployed in 1962, had a CEP of about one-and-a-third miles, but by 1965 a new guidance system that used the new integrated circuits had improved the CEP to about two-thirds of a mile. The Minuteman’s W56 warhead yielded just over a megaton but its greater accuracy would give it more “killing power at the target” than the bigger W49, we thought.
Obviously, despite the fact that the idea of the CEP had some wiggle room in it, you wouldn’t have wanted to be at the target when one of these came in. You wouldn’t have wanted to be in the same county. Even the same country, if you thought about it for a second.
It wouldn’t be just one coming in.
Next: How accurate are our guided missiles? Part Two