designed to provide 165 minutes of pressure in the event of a half-inch diameter hole. An emergency reentry could be initiated within 20 minutes if the shuttle is not docked, 90 minutes if it is docked with Mir, and five hours if it is docked with the ISS. The shuttle takes approximately 60 minutes to land after reentry is initiated.

In the case of a penetration of the Spacehab or Spacelab, the crew would first isolate the damaged module and then decide whether to terminate the mission. If the penetration is not too large and if damaging effects of penetration, such as light flashes and pressure pulses, do not delay their response, the large volume of the Spacelab and the Spacehab provides reasonable time for the crew to evacuate the damaged area (Loftus, 1997a).

Hardware Modifications

To date, the only authorized hardware modifications to the orbiter specifically designed to mitigate the risk from meteoroid and orbital debris are modifications to the radiators in the payload bay doors and the insulation inside the leading edge of the wing. The radiator modifications will reduce the risk that the freon coolant loops will be penetrated by meteoroids or orbital debris, which would force the orbiter to return to Earth. As shown in Figure 6–3, strips of aluminum

FIGURE 6–3 Modification of radiator tube shielding. Source: NASA.

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