kmt-lnh

"It was true that increased heat load destroyed the modified sperm oil in the ATF faster. The problem was that its freshly developed synthetic analogs were performing even worse. Only in the 1980s, a chemical solution to this problem was found, and I highly doubt that it could have been found earlier. Now we have the pieces of the story:

Sperm whales use unusual rheological properties of wax esters in order to control buoyancy, and these properties also make such chemicals an ideal lubricant for extreme pressure applications. When the world relied on whales as a source of hydrocarbons, these were too expensive to use as fuels, and the demand was self-limiting. When the whales were “saved” by petrochemical industry, it was only a short respite. Petrol-powered machinery required new types of lubricants that increased rather than decreased the reliance on sperm oil. Petroleum was plentiful, the cars filled the world, and it is at that point that the whales began to disappear. Literally nothing was done to save these whales until the cars evolved to the point when the engines started to operate at a higher temperature; the latter was caused by the concern about human health and efficiency rather than the well being of these whales."

The Central and Voronezh Fronts each constructed three main defensive belts in their sectors, with each subdivided into several zones of fortification.[148][149][150] The Soviets employed the labour of over 300,000 civilians.[p] Fortifying each belt was an interconnected web of minefields, barbed-wire fences, anti-tank ditches, deep entrenchments for infantry, anti-tank obstacles, dug-in armoured vehicles, and machine-gun bunkers.[151] Behind the three main defensive belts were three more belts prepared as fallback positions; the first was not fully occupied or heavily fortified, and the last two, though sufficiently fortified, were unoccupied with the exception of a small area in the immediate environs of Kursk.[150][152] The combined depth of the three main defensive zones was about 40 kilometres (25 mi). The six defensive belts on either side of Kursk were 130–150 kilometres (81–93 mi) deep.[152] If the Germans managed to break through these defences they would still be confronted by additional defensive belts to the east, manned by the Steppe Front. These brought the total depth of the defences to nearly 300 kilometres (190 mi).