Airman 1st Class Tessa Lyde inspects the electrical system of a self-generating nitrogen servicing cart. U.S. Air Force Airman 1st Class Tessa Lyde, an aerospace ground equipment technician assigned to the 28th Maintenance Squadron, inspects the electrical system of a self-generating nitrogen servicing cart at Ellsworth Air Force Base, S.D., on Sept. 7, 2010. The use of nitrogen in B-1B Lancer aircraft tires prevents water vapor from freezing inside the tire at high altitudes. SHARE: Download: Full Size (0.03 MB) Credit: VIRIN: 970363-B-HUM08-925.jpg Photo Gallery