D180-20236-1

One of the factors that limits the protective capability of the earth cover method is the soil motion that would be induced by a nuclear blast. At about 80-psi air overpressure, shock from the soil motion is sufficient to damage even massive machines. To prevent ground shock damage at higher overpressures, some method of shock isolation or shock mitigation is required. Of the several methods investigated, the cheapest and easiest way of protecting a machine was to completely surround it with a layer of crushable material such as foamed plastic or the metal chips from machining operations. (This protection method is exactly analogous to packing sensitive instruments in plastic foam for shipment.) In practice, during construction or relocation of machines, the foundation of each individual machine would be supported on a crushable pad such as styrene or polyurethane foam. (In the event of a crisis, machines that had not previously been shored up with crushable material would have to be jacked up and supported on wooden cribbing.) Prior to an attack, each machine would be covered with crushable material such as plastic foam, balsa wood, or metal chips. Since metal chips are a byproduct of normal machining operations, there would be no supply problem; Figure 25 illustrates the quantities of such chips produced in a couple of hours by one of the large skin mills at the Auburn facility. The crushable material would then be covered by a layer of soil or sandbags to protect the machine from fire, air blast, and debris. Figure 26 illustrates the application of this protective method to a five-axis milling machine; this protective treatment is also suitable for the spar mills. The autoclaves are somewhat easier to protect as they can be strengthened by internal pressurization and hence would not need a cushion of chips.

A few machines do not lend themselves to the hardening techniques described above. Thinwalled vessels such as the process line tanks would be crushed, and wide unsupported plates such as the skin mill beds could collapse. For these devices, some method is necessary that would permit equalization of the explosive pressures on all sides of the structural elements. To provide this protection, the study team used a technique extracted from the Russian literature whereby the machines are covered with grease to prevent corrosion and then submerged or flooded in water. Using this method, sandbags supported by cribbing could be placed immediately above the surface of the water to protect the machine from debris and limit displacement of the water by the blast wave. The application of this protection technique to the process tank line and to the skin mill is shown in Figures 27 and 28.

The vertical heat treat furnace required yet a different type of protection approach. This furnace is very large and relatively fragile. The furnace itself could be protected by either turning it on its side, packing it with sand, and then surrounding it with sandbags or earth, or by moving it