Construction of a B-21 Raider Environmental Protection Shelter prototype is completed at Ellsworth Air Force Base, S.D., Feb. 26, 2021. Ellsworth AFB was selected as the test site for the B-21 EPS as it provides the most extreme and diverse weather conditions to test the temporary structures. The testing for the EPS prototypes at Ellsworth AFB does not interfere with Air Force compliance to the National Environmental Protection Act/Environmental Impact Statement preparation for the first B-21 Main Operating Base. (U.S. Air Force photo by Airman First Class Quentin Marx)