Mach diamonds appear beneath Space Shuttle Discovery's engines as the vehicle roars after liftoff on STS-116.

Mach diamonds appear beneath Space Shuttle Discovery's main engines as the vehicle roars into the night sky after liftoff on mission STS-116. Mach diamonds are a formation of shock waves in the exhaust plume of an aerospace propulsion system. Liftoff occurred on time at 8:47 p.m. EST. This was the second launch attempt for mission STS-116. The first launch attempt on Dec. 7 was postponed due a low cloud ceiling over Kennedy Space Center. This is Discovery's 33rd mission and the first night launch since 2002. The 20th shuttle mission to the International Space Station, STS-116 carries another truss segment, P5. It will serve as a spacer, mated to the P4 truss that was attached in September. After installing the P5, the crew will reconfigure and redistribute the power generated by two pairs of U.S. solar arrays. Landing is expected Dec. 21 at KSC. Photo credit: NASA/Tony Gray & Don Kight