6. 51 nitrogen (N 2 ) was chosen as the inert gas. To comply with the physiological requirement of a partial pressure of oxygen equivalent to that of sea-level Earth (see Figure 5.3), the pressure was set at 2/5 of sea-level Earth, or 40530 N/m 2 . VI. 7.6: Leakdown Analysis: The ES group then studied the effects of a major leak on the atmospheric pressure and temperature. Scenario: a hole in the hull allows the air to escape into vacuum. It was assumed that the airflow through the hole would be choked, the process adiabatic, and the leak small enough that pressure shocks would not appear within the hull. The calculations appear in Appendix VI.D. The resulting equations relate the pressure and temperature in the hull to the time after the leak began and the area of the hole. The SDA and FT groups were proposing a plate construction for the hull: small (one meter by one meter) plates would be subassembled into larger sections, which would then be assembled to form the hull. The ES group suggested an accident scenario in which a projectile (meteorite, broken compressed gas bottle, turbine blade) would go through the joint between four plates, wrecking those plates and causing a 4m 2 hole. With this figure for the hole area, the pressure and temperature drops with time could be calculated. Figure 6.22 displays these: T 0 is the temperature in the hull; p 0 is the pressure in the hull. P 02 is the partial pressure of oxygen in the hull (half the total in this case). Time is measured from the start of the leak. Hypoxia begins at an altitude of 3050 meters (10000 feet) in the Earth's atmosphere (6.5). This corresponds to a P 02 of 14000 N/m 2 . As seen in Figure 6.22, P 02 in the colony would reach this value 40 minutes after the start of the leak (the line is dashed after this point). The study group felt that this was sufficient time to pinpoint the leak and take emergency measures. Such measures could include moving the population into pressure-tight shelters and sending a repair team to place a temporary patch over the leak inside the hull. If this team breathed pure oxygen from tanks through
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