HOUSTON—After days of delay, Orbital ATK's CRS Orb-4 (for “commercial resupply services”) launched successfully from Space Launch Complex 41 at the Kennedy Space Center in Florida this afternoon. The Cygnus spacecraft took flight atop a ULA-produced Atlas V rocket—an older launch vehicle with a relatively high success rate.
The launch is the first for Orbital since their disastrous CRS-3 launch last year, where a turbopump fault in one of the Soviet-built NK-33 engines powering the rocket’s first stage triggered an explosion that destroyed the launch vehicle and its cargo and also caused significant damage to the launch pad at Wallops Island, Virginia. Orbital switched its launch plans over to utilize an Atlas rocket (which uses more modern, but still Russian-sourced, RD-180 engines) while retrofitting its Atlas rocket design.
Sunday’s successful launch was the fourth attempt this week to get CRS Orb-4 into space. Three previous launch attempts—one per day since Thursday—were scrubbed due to foul weather at Cape Canaveral. The CRS-4 Cygnus capsule is currently en route to the ISS, carrying about 7300 pounds (about 3300kg) of food, hardware, and scientific equipment for the Expedition 44 crew on board the ISS (which includes US astronaut Scott Kelly, who is more than halfway through a year-long stay aboard the station).