ELLSWORTH AIR FORCE BASE, S.D. - Airman 1st Class Tessa Lyde, 28th Maintenance Squadron aerospace ground equipment technician, inspects the electrical system of a self generating nitrogen servicing cart, Sept. 7. The use of nitrogen in B-1B Lancer tires eliminates the potential for water vapor from freezing inside the tire at high altitudes. (U.S. Air Force photo/Staff Sgt. Marc I. Lane)