In the comments, someone asked how long it took for the Russians to develop VT Fuzes, after the Rosenbergs gave them plans1. In attempting to answer this question (which we still have not done), we came across an excellent study and engineering text on VT fuze development by Dr VK Arora. Dr Arora’s book is supposedly available from the Defense Research and Development Office in India ($45 in the USA); we can’t figure out how to buy it, though. If we could, we could arbitrage them on Amazon where they’re going for $99!
Fortunately, DRDO has put the first chapter, which includes the historical stuff, on their website. The rest of the book, the real meat of it, is tech and theory that you don’t really need if you’re in it for the history. (If you do want that stuff, even $99 is a good buy).
It took the US only 2-3 years from giving the project priority to the first Aichi Val down in flames alongside USS Helena. Dr VK Arora notes that India was able to develop VT fuzes and field them for its Army’s 75-mm and 105-mm field artillery over the nine years from 1966 to 1975. However, their first successful design was tested six months after the project started.
Of course, development is eased if you, like the Russians and Indians, but unlike the original British researchers or the Americans who took up their task, know for certain that the product is indeed feasible and practical. Russia knew that, and had some plans and documentation, but were far short of the process sheets they’d need to duplicate all the industrial processes that went into the intricate fuzes.
India had more than the Russians did, with samples of British naval fuzes to study and reverse engineer. But the naval fuzes were much too large for India’s compact WWII-vintage field artillery, which included the following:
- 75mm/L24 pack howitzers, an important mountain gun for India
- The British Royal Ordnance Quick Firing 25-pounder (3.45″/87.6mm) gun-howitzer. These guns were colonial leftovers, and this fuze appears not to have been fielded. (Pakistan, oddly enough, still fields these geriatric guns in quantity).
- The 105mm Indian Field Gun (a domestic development optimized for mobility in India’s varied terrain).
- The Russian D-46 130mm gun
In addition to the Army fuzes, the same Indian labs developed fuzes for the Navy:
- 76.2mm Naval Gun
- 4.5″ (actually 4.45″/113 mm, a British caliber) Naval Gun.
The initial 6-month success story in 1966 was substantially simplified and sped by a thorough understanding of how earlier fuzes, including the WWII vacuum-tube fuzes, worked. The Indian effort was organized much like the American one had been, with scientists in government-funded labs working with the support of the military for testing and industry (in India’s case, nationalized industry) for production. But in the 1960s, transistors offered a way to simplify and ruggedize the fuzes further, and the Indian engineers didn’t miss their chance. In March, 1966, Dr Arora himself at the Defense Research and Development Organization…
…with a team of three other young scientists, PC Nagpal, MN Sen, GJ Chaturvedi and two technicians commenced the work on electronics of the fuze. The team developed a prototype of CW proximity fuze in three months. The fuze electronics developed consisted of a Colpitts oscillator at 220 MHz using an epoxy encapsulated RF transistor, Doppler amplifier, a Schmitt threshold circuit and a transistor switch to ignite the detonator. The fuze oscillator detector was tested for its sensitivity by using a horizontally moving aluminium reflector in the vicinity of fuze. The complete electronics was encapsulated. The oscillator was encapsulated in low density polyethylene. The remaining circuit was encapsulated in an epoxy resin. The electronics was embedded in a plastic nose cone with a metal cap on top of the nose cone which in conjunction with shell body would work as a quarter wave monopole antenna.
The first tests were simple and practical, as the American ones had been, and showed room for further ruggedization. A wax-encapsulated battery turned out to be a weak point, as did the plastic nose cone; then-novel materials such as epoxy resins and fiber-reinforced epoxy solved those problems.
As for the Russian developments? Those still need research. But it’s unlikely it took them much longer than the Indians to get up and running.
- Rosenberg’s VT information was sourced, we believe, from Emerson Electric, where Julius had worked. Along with the atomic information, Julius gave up all of the classified programs Emerson worked on, including the VT fuze. Julius was always the active spy of the pair, Ethel was his partner and support agent but appears never to have had direct access, although she was able to recruit her brother David Greenglass for the atomic espionage task).