Wednesday, July 10, 2013

The R-36


The largest intercontinental ballistic missile ever fielded was a two-stage Soviet rocket called the R-36, which was later upgraded and re-dubbed the R-36M. Both variants were powered by a hypergolic mixture of unsymmetrical dimethylhydrazine and nitrogen tetroxide, could carry a payload of 8 metric tons across the globe in less than an hour, and are among the most terrifying engines of war ever put into mass production. You can read more about the vehicle family here:
R-36

Large rockets are always spectacular when they leave Earth, but the R-36 launches with particular flair. Unlike American ICBMs, which light their engines in the silo and emerge from the ground under their own power, the R-36 is hurled forth with a large black-powder-driven piston like a giant mortar shot. Once the missile clears the surface, the protective piston is thrown away under rocket power, the main engines ignite, and the the R-36's powered flight begins. This may seem excessively baroque, especially for a design from an engineering culture better known for robust simplicity, but it protects the missile and silo from thermal and acoustic damage from running mind-blowingly loud and hot rocket engines in an underground tube. It's also mesmerizing to watch on video:

The payload carried by the R-36 is the stuff that night terrors are made of. Early models carried a single warhead with a yield of up to 25 megatons, while later versions are capable of launching a flotilla of up to 10 warheads in the 500 kiloton range and dozens of decoys, jammers, and other penetration aids. Large single bombs are useful for destroying hardened targets or for causing continent-scale blackouts with electromagnetic pulses in the ionosphere, but clusters of smaller bombs (each still at least 30 times as powerful as the atomic bombs dropped on Japan in World War II) are more useful for destroying large areas like cities.

It's important to understand just how different large thermonuclear bombs are from the relatively small fission bombs deployed in the 1940s. The bombs dropped on Hiroshima and Nagasaki were awe-inspiring devices, but the large single warheads carried by early R-36s were able to unleash a thousand times more energy. James Cameron was a physics major in college, and unsurprisingly the most accurate depiction of large thermonuclear weapons that I know of appears in his movie Terminator 2. It's easy to find on youtube if you want to see it. Suffice it to say that because of the way physics works small bombs deliver much of their energy in pressure waves while big bombs are dominated by a star-like pulse of heat energy. There's an interesting discussion to be had on why this is the case, but the more relevant question is "Why do you want this?"

I'm not suggesting that anyone (or at least any sane person in a position of power) actually wants to burn Moscow, Washington, or Beijing to the ground, but the superpowers have spent trillions of dollars over the last half century to be able to set any city of their choice on fire in 45 minutes or less. Clearly this capability is wanted, and not just by a select few. There's a plausible argument to made that big bombs and fast delivery systems discourage anyone from being dumb enough to start a peer-to-peer war among Earth's armed forces, but it's disingenuous to think of these systems as direct engines of peace. Global diplomatic harmony doesn't emerge in the law of mass action when UDMH is burned with nitrogen tetroxide.

The R-36's history as an enabling device for thermonuclear madness is troubled, to say the least, but out of this thuggish background a much more practical second life has emerged for those missiles decommissioned by the START weapons reduction treaties. For a time during the Cold War some R-36s were equipped not to ride straight to their targets but to linger in Earth orbit for a short time before descending to their destinations. This reduces the missiles' payload, but enables a strike anywhere in the world on any heading from any launch site, confounding the adversary's defenses. This makes nuclear war profoundly confusing in addition to its basic hellishness. When the parking of nuclear weapons on orbit was explicitly banned by the SALT II treaty, this system was phased out, but the R-36 remained a creature worthy of plying the space beyond Earth.

When the statues of Lenin fell, first in Berlin, then in Moscow, and Americans and Russians began sharing space stations and the other fruits of advanced technology, the machines made to drive fright into the heart of every American began lofting their spacecraft into orbit, at a reasonable price. Among other payloads, two experimental space stations designed by Bigelow Aerospace have been launched so far. Weapons of mass destruction remain an infection we'd do well to eradicate, but for now at least there's some progress that shows a more civilized world ahead.

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