The Corner

Re: Dog Calculus

We have readers in EVERY line of work:

“Mr. Derbyshire—In The Corner, you asked ‘How on earth did he solve all those simultaneous differential equations so fast?’ He doesn’t. He does the same thing that we in the Ballistic Missile Defense world do – he approximates. In engineering, unlike math, there is such a thing as ‘close enough.’

“Shooting down a missile and catching a Frisbee in the air are remarkably similar tasks. The size of the opening of the dog’s mouth relative to the Frisbee’s edge profile, and the ability of his head to maneuver when he gets close to his target means that he only has to jump in the general vicinity of the Frisbee to maneuver his head into the path of the disk and snatch it from the sky. In BMD, we estimate the path of the ballistic missile we wish to intercept and shoot the missile to a point close enough to the trajectory of the target so that the maneuvering seeker head of the interceptor can guide itself into the target. We also back that up by supporting a multiple shot model to reduce the probability of a miss, sort of like sending two dogs at different intervals to catch the Frisbee.

“Of course, dogs have been catching Frisbees for decades, while we’ve only really just figured out how to shoot down ballistic missiles in the last few years.”

[Derb] Thanks for what you guys do. You hear a lot that rogue states, if they nuke us, will do so via truck or suitcase bombs. Possibly so. BM technology, however, like any other, gets cheaper and more available all the time. We need defending against it, and that need will only increase.

John Derbyshire — Mr. Derbyshire is a former contributing editor of National Review.

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