The Flying Crowbar

13 Apr

excerpts from  Air & Space Magazine, April/May 1990, Volume 5 No. 1, page 28. Written by Gregg Herken, illustrations by Paul DiMar


Full Article here (definitely worth the read):


 At the dawn of the atomic age, scientists began work on what might have been the nastiest weapon ever conceived.

Once it switched from booster rockets to nuclear power, Pluto would have been a danger to friend and foe alike

“Pluto’s namesake was Roman mythology’s ruler of the underworld — seemingly an apt inspiration for a locomotive-size missile that would travel at near-treetop level at three times the speed of sound, tossing out hydrogen bombs as it roared overhead. Pluto’s designers calculated that its shock wave alone might kill people on the ground. Then there was the problem of fallout. In addition to gamma and neutron radiation from the unshielded reactor, Pluto’s nuclear ramjet would spew fission fragments out in its exhaust as it flew by. (One enterprising weaponeer had a plan to turn an obvious peace-time liability into a wartime asset: he suggested flying the radioactive rocket back and forth over the Soviet Union after it had dropped its bombs.)”

“The idea behind any ramjet is relatively simple: air is drawn in at the front of the vehicle under ram pressure, heated to make it expand, and then exhausted out the back, providing thrust. But the notion of using a nuclear reactor to heat the air was something fundamentally new. Unlike commercial reactors, which are surrounded by hundreds of tons of concrete, Pluto’s reactor had to be small and compact enough to fly, but durable enough to survive the several thousand-mile trip to targets in the Soviet Union.

The success of Project Pluto depended upon a whole series of technological advances in metallurgy and materials science. Pneumatic motors necessary to control the reactor in flight had to operate while red-hot and in the presence of intense radioactivity. The need to maintain supersonic speed at low altitude and in all kinds of weather meant that Pluto’s reactor had to survive conditions that would melt or disintegrate the metals used in most jet and rocket engines. Engineers calculated that the aerodynamic pressures upon the missile might be five times those the hypersonic X-15 had to endure. Pluto was “pretty close to the limits in all respects,” says Ethan Platt, an engineer who worked on the project. “We were tickling the dragon’s tail all the way,” says Blake Myers, head of Livermore’s propulsion engineering division.”

“so many unknowns surrounded Pluto that Merkle decided that it would take a static test of the full-scale ramjet reactor to resolve them all. To carry out the tests, Livermore built a special facility in a desolate stretch of Nevada desert close to where the lab had exploded many of its nuclear weapons. Designated Site 401, the facility — built on eight square miles of Jackass Flats — rivaled Project Pluto itself in ambition and cost.”

“Just to supply the concrete for the six- to eight-foot-thick walls of the disassembly building, the U.S. government had to buy an aggregate mine. It took 25 miles of oil well casing to store the million pounds of pressurized air used to simulate ramjet flight conditions for Pluto. To supply the high-pressure air, the lab borrowed giant compressors from the Navy’s submarine base in Groton, Connecticut. For a five-minute, full power test, as much as a ton of air a second had to be forced over 14 million one-inch steel balls in four huge steel tanks raised to 1,350 degrees Fahrenheit by oil-burning heaters.”

The 25 miles of oil well casing needed to store air for ramject simulations dominated Pluto's test site at Jackass Flats.

“Meanwhile, at the Pentagon, Pluto’s sponsors were having second thoughts about the project. Since the missile would be launched from U.S. territory and had to fly low over America’s allies in order to avoid detection on its way to the Soviet Union, some military planners began to wonder if it might not be almost as much a threat to the allies. Even before it began dropping bombs on our enemies Pluto would have deafened, flattened, and irradiated our friends. (The noise level on the ground as Pluto went by overhead was expected to be about 150 decibels; by comparison, the Saturn V rocket, which sent astronauts to the moon, produced 200 decibels at full thrust.) Ruptured eardrums, of course, would have been the least of your problems if you were unlucky enough to be underneath the unshielded reactor when it went by, literally roasting chickens in the barnyard. Pluto had begun to look like something only Goofy could love.”

“The Navy, which had originally expressed an interest in firing the missile from ships or submarines, also began to back away from the project after successful tests of its Polaris missile. Finally, at $50 million apiece, there were doubts that SLAM was worth the price. Pluto was suddenly a technology without an application, a weapon without a mission.”


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