Comments about technological history, system fractures, and human resilience from James R. Chiles, the author of Inviting Disaster: Lessons from the Edge of Technology (HarperBusiness 2001; paperback 2002) and The God Machine: From Boomerangs to Black Hawks, the Story of the Helicopter (Random House, 2007, paperback 2008)

Monday, September 6, 2010

Shaped charges, and a call for new engineers

In the last five years when researching stories on technology I've commonly heard concerns from industries about a demographic crisis in getting enough people with specialized training, now that old hands are retiring: such as inert gas welding, underwater engineering, numerically controlled machinery, and explosives. Here's a Wash Post article where this concern has come up in air traffic control. Sort of a "human infrastructure" crisis.

When researching my piece on shaped charges, I heard from both the explosives companies and the mining school at Rolla, Missouri, that there's a strong demand for young explosive engineers. If you know of high-schoolers interested in the subject, have them take a look at Rolla's summer school in explosives. I interviewed Prof. Paul Worsey of Rolla ... very helpful! Here's a link to his series on explosives for Discovery.

Re: shaped charges, here's a Wikipedia link ... the penetrating effect comes not from a jet of "white hot plasma" but rather in how it forges a rod of metal from a sheet of metal (it's hot, but not necessarily molten) and projects it forward at supersonic speed. When striking armor plate, this rod actually shoves aside molecules of metal in the armor and opens a cavity in the direction of travel. In a 1997 military test, one shaped charge opened a hole through 11 feet of armor plate. Numerically, the vast majority of shaped charges now manufactured are pocket-sized devices used in the oil and gas industry, quite effective at perforating steel pipe and opening up rock formations to production.

For armchair historians interested in the history of the WWII bazooka (a marriage of the shaped charge warhead and the solid fuel recoilless rocket), here's an excerpt from my article. Two things to note: first, the M1 was not a great antitank weapon but still proved its worth in taking out pillboxes and giving heart to our infantry; second, how very quickly industry was able to produce the weapons in quantity (GE had 30 days from working out the first prototype manufacturing article, to finishing the production run). I might add some posts in the future on lessons in rapid production from WW2, by far the most productive period in US history.

By late 1941 the Army had a lightweight warhead able to destroy the era's lightly skinned tanks, but it lacked a delivery system with which an infantry-man could confront an oncoming tank. Meanwhile, two American Army officers had overcome all hurdles to build a workable shoulder-fired rocket launcher. But they had no lightweight, armor-busting warhead to fire. Soon thereafter these two projects would intersect and spawn almost a half-million offspring known as bazookas.

The search for an effective shoulder- fired rocket launcher had begun long before, most notably in 1866 with the pyrotechnics manufacturer Gustavus Adolphus Lilliendahl and the one- armed whaling captain Thomas Roys, who began selling a shoulder-launched rocket system. It fired an explosive- tipped rocket intended to harpoon whales at distances up to 130 feet. In both appearance and function, the whaling rocket was a closer kin to the eventual bazooka than the solid-fueled, man-portable launch weapon developed by the rocket pioneer Robert H. Goddard during the First World War.

Unfortunately for Goddard, the Armistice came less than a week after he demonstrated his rocket, and the Army declined to proceed. After recovering from tuberculosis, Goddard shifted to liquid-fueled rocket research. But his coworker, graduate student Clarence N. Hickman of Clark University, continued in the field. (During the war, the university would support more rocket research at its Allegany Ballistics Laboratory in Rocket Center, West Virginia.) And in 1931 the Army detailed Maj. Leslie Skinner to serve as a one-man rocket research center. Skinner's program doubled with the addition of Lt. Edward Uhl, expanding again in 1940 after Hickman pointed the new National Research Defense Committee toward rocket research. Working in a basement lab at George Washington University, Uhl and Skinner progressed from a closed launcher with tremendous recoil to an open- ended tube that allowed each rocket to discharge its exhaust out the back.

Top Army Ordnance officials happened to be visiting Aberdeen in May 1942, when Skinner and Uhl were firing their prototype at a moving target. Although the launcher only mounted dummy warheads, the flame and whoosh drew their attention. Skinner gamely let them test-drive it even with its rudimentary gunsight. On his first try, Gen. Gladeon Marcus Barnes, who headed weapons research and development at Ordnance, hit the target squarely. “The other staff people fired until all our rounds were gone,” Skinner would recall. “Right there and then the Bazooka was ordered into pilot production design.” In one of the fastest procurement decisions ever, the Army contracted a few days later with General Electric for 5,000 M1 launchers, and with Edward G. Budd Manufacturing Company for 25,000 M6 rockets employing a shaped charge like that in the M9 rifle grenade.

The companies had 30 days to deliver. By 1942 much American war production happened at a sprinter's pace, but this particular job gave a new meaning to “rush order.” Working 24 hours a day, General Electric engineers spent more than two weeks building and testing a dozen prototypes before the Army approved a production model. That left eight days for a converted refrigerator factory in Bridgeport, Connecticut, to turn out the goods. The supply chain included police officers who picked up pieces at the airport, hurled them in the trunks of their squad cars, and raced to the factory. General Electric finished with 89 minutes to spare.

At first the troops dubbed it the “Buck Rogers gun” but then settled on “bazooka,” because it resembled a musical instrument of the same name that movie and radio comedian Bob Burns had improvised out of pipe. The tube was made long so that the propellant would have burned out by the time the rocket left the tube, thus avoiding injury to the operator's face by exhaust flame. The Army's publicity machine was quick to celebrate this paragon of American ingenuity: the bazooka was a miracle weapon, Ordnance chief Gen. L. H. Campbell Jr. told reporters in March 1943, enabling any GI “to stand his ground with the certain knowledge that he is the master of any tank which may attack him.”

In truth the early bazookas fell short of actual panzer-stopping power. Commanding officers, including Lt. Gen. James Gavin, reported back to Ordnance that German tanks had flattened GIs who had stood their ground. Moreover, the rush of battle easily damaged the long tube. The battery circuit wasn't reliable, many troops lacked training, and some rockets misfired or bounced off their targets. But even the early M1 models were good pillbox wreckers; after the M9A1 was available, Allied soldiers were able to disable light and medium tanks, some-times working in concert with tracked tank destroyers. All told, American companies produced 441,000 bazookas and 15 million rocket warheads.

After the bazooka appeared, the Germans fielded their own tank- busting rockets: the shoulder-fired Panzerschreck (tank terror) and the short-range, single-use Panzerfaust (tank fist). Franz Thomanek insisted after the war that these were no mere knockoffs of the M1 and M9 bazookas. (This is probably true in the case of the Panzerfaust.) In any case, most GIs who tried both German and American models agreed that the bigger German weapons inflicted more damage than their 2.36-inch-diameter counterparts.

Reacting to the competition, the Army commissioned the M20 Super Bazooka, but this did not materialize in time for World War II, even arriving a bit tardily on Korean battlefields. Task Force Smith and other American units first thrown into action against the North Korean 105th Armored Brigade found that their war-surplus M9A1 bazookas had no effect on the Russian-built T-34s. On its arrival in September 1950, however, the Super Bazooka helped turn the tide, remaining in use until the one-shot, disposable M72 Light Antitank Weapon replaced it during the Vietnam War.

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