as the thermal control system compartment, the high-pressure oxygen/nitrogen tanks, the gyrodynes, or the plasma contactors.

If the code determines that a penetration will occur, it checks for seven possible failure modes that could result in crew or station loss. These are:

  • immediate critical crack propagation (unzipping)

  • loss of control or structural failure due to venting

  • penetration of critical equipment

  • crew injury from fragments

  • crew injury from light flash and overpressure

  • individual crew hypoxia and multiple crew hypoxia from rescue attempts

  • delayed loss of the station resulting from irreparable failures of critical systems

The code determines the overall likelihood of loss by dividing the number of penetration combinations resulting in a loss by the total number of penetrations.

This tool also has been used to perform preliminary evaluations of the effectiveness of various escape protocols and of the efficacy of having personal oxygen bottles readily available. Figure 5-1 depicts current MSCSurv predictions for the probability of loss in the event of a penetration under baseline assumptions for three cases: where hatch closure is used to isolate the half of the station in which the leak has occurred, where the individual leaking module can be isolated as the crew proceeds to the safe haven, and where the leak can be immediately located. Figure 5-2 shows MSCSurv predictions for the same cases if oxygen masks are readily available to the crew.

FIGURE 5-1 MSCSurv baseline predictions of probability of loss. Source: NASA.

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