From H. Wroe
Moulsford, Oxfordshire
Philip Chien states that arc welding in the vacuum of space is impossible (“There’s a hole in my spacecraft”, 19 April, p 42). This is not so. I published a paper almost forty years ago (British Journal of Applied Physics, vol 9, p 488) based on work done at the Metropolitan-Vickers Electrical Company, describing a method of stabilising an arc discharge in vacuum using shaped magnetic fields. The field confined the electron emission sites, the cathode spots, to a small area of a cold cathode, and confined the arc column so that the energy density at the anode was high enough to melt it.
Several welds were made in a vacuum chamber and the method could have been perfected had anyone been interested at the time. It is potentially a much simpler and cheaper method than the hand-held electron gun described in the article.
Perhaps NASA could have saved a lot of money by searching the old literature.
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