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How to build railguns and coilguns, continued...
 
MIT Professor and Students Build Mass Driver Coilgun

Thus a 1976 NASA contract to build a coilgun, “Mass Driver I.” The coilgun team, led by M.I.T. magnetics professor Henry Kolm, unveiled it at O’Neill’s May 1977 Princeton Space Manufacturing Facilities Conference. It was eight meters long with a two meter propulsion section and a six meter braking section.

They set it up in the lobby of Chadwin Hall on the Princeton campus and a crowd of space enthusiasts, including me, gathered. A student fished the gun’s copper-coil-wrapped bucket out of a tub of liquid nitrogen, slid it into the barrel, and bang! The bucket reached a peak speed, they estimated, of 140 MPH (63 m/s) and appeared instantaneously, so it seemed, at the far end of the gun. We cheered and clapped.

After the Princeton event, Kolm’s team began building Mass Driver II with a goal of reaching 112 m/s. O’Neill’s nonprofit Space Studies Institute pledged some funding, but Kolm needed more, from NASA, he hoped, to complete it.

mass drivermass driver photo

Figure: Mass Driver I, a coil gun.

Later in 1977, Sen. William Proxmire, famed for his “Golden Fleece” awards for wasteful government spending, discovered O’Neill’s space colonies project. The Senator promptly appeared on the prime time TV show Nova, and thundered, “Not another penny for this nutty fantasy.” NASA reacted by pulling the plug on all its space colonies projects, including Kolm’s mass drivers.

It must have seemed like an act of Providence to O’Neill and Kolm when Fair contacted them and said he hoped to fund them.

And then, another act of Providence: Fair discovered Prof. Richard Marshall, a New Zealander who was a professor at Australian National University in Canberra.

Back in the 60s, Marshall had rescued the University’s 550 MJ homopolar generator project. These are so named because their magnetic fields have the same polarity at every point and this generates a DC output. The Canberra homopolar generator was designed to deliver its power in a pulse of two MA. Because of this ultra high current, in place of a typical generator’s brushes, the original design made electrical contact for the output with a liquid metal alloy of sodium and potassium that is liquid at room temperature. During testing, this incredibly corrosive liquid exploded, permanently blinding one of the experimenters.

Marshall persuaded them to let him rebuild it with brushes based upon the starters used by ordinary motor vehicles. Astonishingly enough, this worked. “I’m an engineer, not a scientist” he says, “and I’m good at finding lucky solutions to difficult problems.”

Now a hero, Marshall won funding to build the device of his dreams: a 5-m railgun, with the 550 MJ homopolar generator as the power source. In 1977 Marshall accelerated a 3-gm Lexan projectile to a world record 5.9 km/s. He says the projectile “looked like a meteorite” as it flew out the barrel.

Strangely enough, Marshall’s world record still stands. Therein lies quite a story. Perhaps one of you reading this is destined to finally break the record.

And then, Marshall promptly lost his funding. He went on leave from the University, moved to the U.S.  and joined a Westinghouse pulsed power project in Pittsburgh, which is where Harry Fair found him.

The 1977 collapse of Kolm’s and Marshall’s funding was not the first time that EML research had stalled, nor would it be the last.

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       © 2013 Carolyn Meinel