You Might Want to Know: How accurate are our guided missiles? Part Two
You Might Want to Know: How accurate are our guided missiles? Part Two
After we had done a good bit of “weapons effects” testing of our nuclear weapons we calculated that doubling the accuracy of our nuclear missile warheads would increase the radiation damage by a factor of four and the blast damage by a factor of eight. Obviously, even though nuclear weapons damaged huge areas, we needed to keep working on accuracy.
By 1959, we had stationed over in Europe and aimed at Moscow, among other places, our Thor and Jupiter Intermediate Range Ballistic Missiles. The Thors we put in England, the Jupiters in Italy and Turkey. Those were the only countries in Europe that allowed us to station them there.
By 1960, here at home, we had Atlas ICBMs ready to go and were taking the Jupiters and Thors out of Europe.
After 1961, we could also call on Intermediate Range missiles called Polaris that could be launched from submerged submarines. The Polaris missiles had a shorter range than the ICBMs, about the same as the Thors and Jupiters, but they also could be launched from oceans much closer to the Soviet Union.
To begin with, the Polaris missiles were less accurate than the Atlas ICBMs. One problem here was that the submarines didn’t have a way of knowing exactly where they were when the missiles were launched.
Our ICBM guidance was better to begin with. By 1969, it had improved even more.
The measure we used for accuracy was the one the Army artillery used, the Circular Error Probable. The CEP is the radius of the area we figured the missiles, or the rounds, would land in half the time.
With every new ICBM the CEP we’d assigned to it had gotten smaller, sometimes by a little, in the end by a lot. The CEP of the Atlas D, our first ICBM, was almost two miles. The CEP of the Atlas E and F was only a mile. The CEP of the Titan I and Titan II ICBMs was only two-thirds of a mile. The CEP of the Minuteman I, our first solid-fueled ICBM, introduced in 1962, was about a mile. But the Minuteman II had a CEP of only about a fifth of a mile, the length of only two football fields. After flying more than six thousand miles.
All these missiles used some kind of “inertial guidance system” that used gyroscopes. These were supplemented by radio signals at first. Then entirely internal. And finally helped a lot by the new integrated circuits. Computers.
Some of our internal inertial guidance systems were improved with a “star tracker.” While the missile was flying, this system could use a photocell to look up through a window and locate certain stars. This information could be used to correct the path of the missile. I know. Pretty amazing.
By the late 70’s, the biggest improvement. Our military had in place a “Global Positioning System.” They’d put a number of GPS satellites into orbit, and if a GPS receiver on earth could get signals from four of them, it could locate itself very accurately indeed. Also amazing.
At first, this GPS system was reserved for our military. President Clinton made it available to the rest of us. Now, from anywhere, it can get us into our driveways.
Could it get the warhead of an ICBM into our driveways? Maybe not quite. When the warhead of an ICBM arrives, it is travelling at fifteen thousand miles an hour, maybe more. A cruise missile travels much more slowly. A lot more likely there.
In the 80’s, the multiple-warhead Peacekeeper ICBMs that we deployed for a short time used a greatly improved inertial guidance system called the Advanced Inertial Reference Sphere. This missile’s ten W87 or W88 warheads (with yields of three-hundred or four-hundred seventy-five kilotons, twenty- to more than thirty Hiroshimas) had a CEP of just over one-hundred thirty feet, it was claimed. And each of the Peacekeeper’s ten warheads could be independently targeted.
When the Cold War ended, we decided we didn’t need the Peacekeepers. Maybe we could save a little money there.
But we weren’t done. Later, a little while after the end of the Cold War, we went ahead and deployed some new Submarine-Launched Ballistic missiles we’d been developing for a while now called Trident II D5s. The D5 had a CEP of three hundred feet. For a warhead that yields four-hundred seventy-five kilotons, more than thirty Hiroshimas, a CEP of three hundred feet ought to be able to get the job done.
Fourteen great big Ohio-class submarines, each almost as long as two football fields, were built for the Trident IIs. Each of those submarines had twenty four missile tubes. Each Trident II missile could carry eight to ten W88 warheads. Two hundred-forty warheads, then, yielding four-hundred seventy-five kilotons each. That meant every one of those fourteen Trident submarines could deliver one-hundred fourteen-thousand kilotons on the enemy, seven-thousand six-hundred Hiroshimas, all within three hundred feet of the target.
Four other Ohio-class submarines we built could each launch one-hundred fifty-four cruise missiles from under water. Those missiles might be even more accurate.
Under wartime conditions, would our missiles turn out to have the accuracy that was being claimed for them? Impossible to know. But if we weren’t entirely confident that our missiles and warheads would have the accuracy we were claiming for them, or if we thought some of them might misfire or be shot down or something, we could just fire more missiles at a target.
In the 70’s and 80’s, we had bought and built more than enough warheads to fire more than one at the targets we now had on our Strategic Target List for communists, even though by now we had thousands of targets on the list.
When it came to Moscow, we weren’t going to take any chances, of course.
Still, in the late 80’s, civilian investigators from the Defense Department were more than a little surprised to discover that our secretive Strategic Air Command targeting committee had been assigning hundreds of nuclear warheads to Moscow alone. Really? Hundreds of strategic warheads many times more powerful than the bomb that destroyed Hiroshima? On one city?
Anyway, that was the plan they’d come up with, the Defense Department’s investigators learned.
The Soviets’ plan was probably a lot like ours.
Next: I. ICBMS arriving