American Institute of Aeronautics and Astronautics
James A. Marusek (Nuclear Physicist & Engineer)
[Abstract] Disaster preparedness is the second line of defense for comet or asteroid impact events. If efforts to deflect or destroy the inbound threat fail or if the mitigation window is too short, disaster preparedness may be the only or last line of defense. Disaster preparedness consists of evacuation, sheltering and post impact recovery. In general, the majority of impacts are small, local events with a very limited area of destruction. Under these circumstances, a disaster preparedness plan will be similar to a hurricane evacuation plan. Initially the hurricane is spotted and assessed by aircraft, ships and satellites but its path is initially unknown. As the hurricanes path begins to be defined, the government will issue general warnings covering a large swath of land that might be potentially threatened. Individuals are informed of the threat and begin preparation. As data resolution becomes sufficiently accurate to make projections of where the hurricane will strike land, specific warnings are issued which describe a narrow band of coastline as the target. The affected area is then evacuated. The same approach will occur during a small to medium impact threat. A critical element for implementing disaster preparedness is identification of the point-of-impact with sufficient warning time to allow evacuation & sheltering plans to be implemented. In general, the delay Doppler radar sites at Goldstone and Arecibo are key. These capabilities can reduce trajectory uncertainty to the level required to make very accurate point-of-impact (location/time) predictions. The best course of action to survive an asteroid or comet impact is to evacuate the zone of destruction prior to the time of impact. The zone of destruction is defined as the area that will receive a blast wave 1-psi or greater overpressure and if the impactor strikes the ocean, the area affected by the tsunami. But evacuation may not always be an option. Geological and governmental barriers, point-of-impact uncertainty, limits on modes of transportation and limited time may preclude effective evacuation. Very large impactors (several miles in diameter) may rain destruction over the entire planet. Alternative options include sheltering in pre-existing man-made shelters or natural shelters or the construction of expedient blast shelter to survive the immediate effects of the impact. A 50-psi overpressure blast shelter can offer protection for approximately 98% of the area within the zone of destruction. Both the Soviet Union and the United States developed designs for construction of expedient blast shelters using commonly available material under short execution timeframe for protection against a nuclear threat. These designs should be updated, tested and the construction details incorporated into impact disaster preparedness plans. Large impact events may produce great damage to the infrastructure, making recovery operations extremely difficult and amplifying the level of the disaster. Most of the damage from the 1906 San Francisco earthquake came from the fire that followed. The plan will define steps that can be taken in advance of the impact to minimize secondary damage. Examples are: lowering the water level in major reservoirs/dams, closing off and securing all underground oil/gas mains, taking nuclear reactors off line, and individuals shutting off gas lines to residences. Other pre-impact planning discussed in this paper include: shelter provisioning, relocation of key industries and key assets, managing transportation choke-points, relaxation of border controls, mass migration, alternate evacuation routes, national shelter plan, roles and coordination of federal/state/local government and reliance on individuals & families, and threat mitigation from triggered secondary disasters.