Airman Magazine's official history of Cheyenne Mountain: 25-ton steel blast doors that seal in 40 seconds, and an underground city under about 2,000 feet of granite.
the station's iconic 25-ton steel doors remain the same, ready to seal the mountain in 40 seconds to protect it from any threat. The underground city beneath 2,000 feet of granite still provides the protection to keep the station relevant
Airman Magazine's official history of Cheyenne Mountain: 25-ton steel blast doors that seal in 40 seconds, and an underground city under about 2,000 feet of granite.