The door to the Survival Condo closes slowly, sending a resounding thud through the concrete parking garage. Those inside have surrounded themselves with walls up to 9 feet thick, ready to withstand a nuclear explosion, the eruption of Yellowstone's supervolcano or an outbreak of avian flu. Larry Hall, project manager and owner of the Luxury Survival Condo Project, says he feels safer with the doors closed. He says he's sold all 12 luxury condos in the former Atlas missile silo — which once housed a nuclear warhead — not far from Concordia, about two hours north of Wichita. He's working on a second silo. A full-floor unit is 1,820 square feet and costs $3 million. A half-floor unit, at 900 square feet, costs $1.5 million. Survival is a unifying cause. Hall said his owners come from a variety of political beliefs and include people in international business, architecture, law and medicine. He said the owners don't do interviews; efforts to reach them were unsuccessful. The survival