Inventions: Plasma Torch
Photograph courtesy of Dartmouth College archives
Inventor: Professor James Browning ’44
By Lee Michaelides
Half a century ago Thayer Professor James Browning ’44 was nicknamed Hanover’s firebug for his study of flame stability and combustion. In early work on Project Squid, a government-funded study of propulsion, Browning experimented with methyl naphthalene, which smells like gasoline-soaked mothballs. Not only did his lab reek, but news clips from the era reported that as Browning “passed people on the street on his way homeward, he was the subject of many curious glances from people who suddenly realized who was defiling the usually ‘pine-scented’ atmosphere of Hanover.”
Browning will be remembered best not for his smell but for inventions that fired up the Upper Valley economy. In the 1950s he created a plasma torch that produced flames twice as hot as the sun’s surface. Passing nitrogen or hydrogen through a high-intensity electric arc, the torch cut metal like butter. Browning and Thayer colleague Merle Thorpe founded Thermal Dynamics Corp. to manufacture the device. Within three years the start-up had sales of $1 million. A decade later, Thayer Professor Robert Dean and Richard Couch ’64, Th’65 formed Hypertherm Inc. to produce a water-injection plasma torch that was nine times hotter than the sun. Today that company employs 500 people.
Meanwhile, Browning invented a high-temperature rocket drill called the “Thermoblast.” In 1977 he used it to pierce Antarctica’s 1,400-foot-thick Ross Ice Shelf so scientists could study the water underneath. Drilling time: nine hours — a cool use of a hot technology.
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CORRECTION: “A decade later, Thayer Professor Robert Dean and Richard Couch ’64, Th’65 formed Hypertherm Inc. (AND USED MR. BROWNINGS’ IDEA) to produce a water-injection plasma torch that was nine times hotter than the sun. Today that company employs 500 people.”
Dean and Couch went beyond Browning’s idea.
According to Hypertherm’s history page:
Hypertherm’s roots date to 1968, when Hypertherm president Dick Couch and an associate, Bob Dean, made the greatest breakthrough since the initial discovery of plasma cutting fourteen years earlier. They discovered that by radially injecting water into a plasma cutting nozzle, they could create a narrower arc, capable of cutting metal with a speed and accuracy never before seen. In addition, two issues that had plagued the industry from the start–the accumulation of dross and a phenomenon called double-arcing–were virtually eliminated.
Improved Plasma Cutting
Hypertherm’s new water injection technique introduced another first to the industry. Instead of relying on several different types of gas for cutting, the Hypertherm system relied on only one: nitrogen. This single gas requirement made plasma cutting more economical and easier to use since customers no longer had to purchase and stock several different types of gas. Customers also saw a marked improvement in nozzle life because steam from the water helped to cool and protect the nozzle, significantly slowing down its wear rate.
Hypertherm Patents Technology
Mr. Couch quickly patented his new radially injected water technique and unveiled Hypertherm’s very first plasma cutter, the PAC400. For the first time, plasma was a real option for people needing to quickly and cost-effectively cut through metal.
—The Editors