Rocket Science and Deterrence

A Minuteman III Launches out of Vandenberg AFB at night, photo USAF

Most of my posts to date have been “War Stories” from my days as a USAF pilot. There are reasons for this. Airplane stories are inherently interesting, easy to follow, and therefore seem to be what my readers like the most.

However, I have expended many more years as a Cold Warrior in the role of “Rocket Scientist”. My expertise has been Intercontinental Ballistic Missiles (ICBMs) -- mainly in propulsion and guidance.

So why not a few rocket stories? Well, really, ICBM stories can be hard to follow, complicated, and complex. Bernard Quatermass aside, they are not nearly as adventurous as jet airplane stories. (Thank goodness!)

As you get ready to tell the story, the first thing you have to explain is that the ICBM mission is to make sure it is never used. (Er, what?)

The ICBM mission cannot be fully understood without talking about Sea Launched Ballistic Missiles and nuclear bombers. So that gets complicated. 

The engineering is complex and interrelated on many dimensions. You cannot replace any single component in the weapon system without considering the effects on the whole. 

So how can I explain rocket science to my broad audience in just a few words, and make it interesting?

Yet, when I go to universities and engineering societies and speak on this subject, folks seem to be entertained and enlightened. So I will give it a go here as well.

The mission is deterrence. That is, we are telling our adversaries that a large-scale attack on our country will carry an unacceptable price: We will retaliate with our own nuclear weapons. For this strategy to work, we have to have a weapon system that has this ability. And we need to have a government willing to make the implicit threat. 

Another way to look at this mission is that we are aiming a gun at the person that is aiming a gun at us. A standoff. You’ve watched Westerns, right?

Name that Movie!

Yeow! That doesn't sound good! How’d we get into this fix, anyway?

At the end of World War II, we faced a very different future for our country than the one we envisioned before the War. In fact, we were participants in creating this new reality. After the war, anyone paying attention knew that any country anywhere in the world could be successfully bombed from the skies. You might be able to fight off a few bomber aircraft, but most would probably get through. And if the enemy used V-2 rockets, there was really no way to defend against those. 

Starting in the early days of the war, many dozens of aircraft sorties were needed to do even minor damage to a nation. However, by the end of the war, we had nuclear weapons. One city, one bomb, one airplane.

On top of that, any remaining illusions that our country was protected by two great oceans was completely destroyed when the Soviet Union launched Sputnik. This was a feat that we had yet to accomplish at that point in time. And, by the way, why should we think we would win a race with other countries in developing intercontinental rocket weapons? Our rockets had been blowing up on the launching pads!

History had taught us that any country that is caught with its defenses down will be taken — or at least lose a great deal of its national sovereignty and its citizens’ freedom. And there were no defenses against the threat we now saw in nuclear weapons descending from the skies.

The only solution we could come up with was to be as well-armed as our adversary, and be prepared to use it, so as to deter them from using it. 

As it turns out (yes, President Kennedy understood this) in a mutually helpful situation, our race to the Moon occurred in parallel with a race to develop ICBMs. To create ICBMs, we had to overcome a dozen truly major technical hurdles such as inventing precision on-board guidance, formulating stable high-energy fuels, figuring out how to re-enter Earth’s atmosphere without burning up, and so on. You may recall that in our race to the Moon we had a lot of help from former Nazi rocket scientists. These were the same scientists who created and employed V-1 and V-2 rockets in attacks on Great Britain. A major difference between the Moon race and ICBMs was that we were producing hundreds of ICBMs, creating a need for a high rate of production of cutting edge technologies such as the newly created integrated circuits. (For extra bonus points, anyone remember what rocket pushed the Gemini astronauts into orbit? Yes, a Titan ICBM.)

There are those who think a flying saucer crash at Roswell gave us integrated circuits and other futuristic tech. The press of history and the necessity to create ICBMs pushed technology ahead, not little green men.

In the 1960’s, the Air Force was the major customer of Texas Instruments,

these new integrated circuits were critical to rocket nav

We did succeed in creating the weapons needed for deterring our adversaries. And, in parallel, we were refining our understanding of the mission of deterrence. The calculus of nuclear deterrence can get complicated. But here is a simple scenario to illustrate the basics.

With 450 land based nuclear-tipped missiles across the northwestern United States, any large-scale enemy attack would need to destroy these weapons immediately upon starting hostile actions. This would deplete even our largest enemy’s arsenal. And we would still have our bombers and submarines (and surviving missiles) available to retaliate. Thus, the attack will not come. 

And, by the way, such an attack would certainly leave no doubt about our enemy’s intentions and strategies.

This example is in today’s numbers. At one time there were many, many more ICBMs on duty. There are, of course, good reasons to want to reduce and eventually eliminate these weapons. The most important being, the nuclear bombs are environmental disasters beyond imagining. But we need to be careful that in reducing our numbers of nuclear weapons, we do not entice others to attack, thus bringing about the very disaster we are trying to avoid. 

It comes down to the question: Can we separate the mission of deterrence from the nasty weapons we use to ensure it?

I will leave the deterrence calculus for now, and let’s get to the rocket science question: How does an ICBM work?  Basketball.

Yes. Basketball. It is really that simple. If a basketball can be tipped off your fingers into the air in the right point going the right direction at the right speed, it will hit the hoop. An ICBM puts the warhead in the right place, in the right direction, going the right speed so that it will lob over half the Earth and hit its target. 

A notional drawing of an ICBM re-entry vehicle, containing a nuclear bomb, on a ballistic trajectory

Our current and only ICBM is the Minuteman III, deployed in 1972 and constantly tweaked piece by piece to make it viable well into the future. For instance, we have completely replaced the solid rocket fuel twice so far.

In this exaggerated photo, a platform inside the rocket keeps it’s position

despite the rocket turning around the Earth

The guidance system on this missile consists of a set of velocity sensors mounted on a platform that remains in one position relative to the Earth as the missile flies (see illustration). In the drawing, this is illustrated by showing a spring scale and weight measuring acceleration in one direction no matter how the rocket turns around the Earth. Thus, the on-board computer knows the direction of the sensors that measure speed. The same computer determines when the missile has reached the right place in the sky at the right speed and in the right direction, and then releases the bomb (encased in an atmospheric re-entry vehicle). This is exactly like the basketball player releasing the ball  when she knows it is headed in the right direction at the right speed to score.

Gyroscopes in the platform keep it pointed in the same alignment with respect to the earth. The real sensor we use to gauge speed is an gyroscope with a weight hanging off of one end. As it turns out, the precession of the gyroscope under acceleration directly measures velocity.

How accurate is it? Very. And spoof-proof. GPS, for instance, is only used during test flights to better measure the precision of the  guidance instruments.  

The Cold War is over, they tell me. But we still have nuclear tipped ICBMs on alert. And the Russians have theirs as well. The good news is we have been steadily reducing our inventory of these weapons. 

Graph from

http://www.defense.gov/npr/docs/10-05-03_Fact_Sheet_US_Nuclear_Transparency__FINAL_w_Date.pdf

We need to find a way to completely eliminate nuclear weapons. Nasty, dirty things. But  this should not be confused with abandoning the deterrence mission. The men and women and technology of deterrence has kept this nation safe and avoided another world war for almost 70 years.  

So what is the answer? You tell me.

Your comments requested below.

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Pop culture note: If you have not seen the movie “Dr. Strangelove”, you must stop what you are doing and watch it now. I have yet to find a person of any persuasion or political belief that does not love this parody of the Cold War and nuclear weapons. It contains much truth. One word of caution. Like all movies about nuclear crisis, the methods of releasing our nuclear weapons for use are not anywhere near as easy as depicted.