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After a brief hiatus in 2010, United Launch Alliance (ULA)

June 6, 2018 by Devin Jones

After a brief hiatus in 2010, United Launch Alliance (ULA) resumed the Apollo program in November 2011. Today's decision to retire the Thor rocket, and to abandon the Delta II, marks a bittersweet end to a remarkable American rocketry journey. While the launch of the Thor was an extremely significant milestone for US spaceflight, it still had a long way to go before it could accomplish more than 100% of its mission.

The Thor launch was the first in the program to be launched from the launch pad at Vandenberg Air Force Base. The Thor took off from the space center at 3:11 a.m. ET and landed in the desert at 4:12 a.m. ET. The launch marked the first time a rocket was deployed from a launch pad outside the United States in over nine years. The rocket used a rocket engine powered by the International Space Station (ISS) and was powered solely by the commercial launch vehicle RD-180 (the "DST-180" was also launched from the launch pad). During the initial stage burn, the engines ignited and began a series of thrust reversals on to the rocket's two main engines, the Atlas V-2 and the Delta II. During each reverse, an electrical charge ignited on the rocket's propellant tank which was ignited by the engine's combustion of the RD-180. The engine's secondary engine, the combustion chamber, was powered by the satellite's own lithium-ion battery pack.

From the launch pad to the launch pad at Vandenberg Air Force Base, the rocket is still powered by the RD-180, and the only way it can get to its final destination is from NASA's Cape Canaveral. The Atlas V-2 is the first launch vehicle to be delivered to the US by the Cape, and the second launched by the Falcon 9 rocket. The Atlas V-2 is based on a version of the Atlas V—the first commercial rocket to use the Atlas V—designed and built by SpaceX. It is the second to have the Atlas V-2 engine tested in orbit.

The Delta II rocket takes off from Cape Canaveral on the first day of its maiden flight in January 2012. The Delta II first traveled to the space center at Vandenberg Air Force Base on November 28, 2012, and landed at the Vandenberg launch pad on January 21, 2013. The second flight was delayed for 15 days after the first flight and also during the launch. The flight took place at the Cape-based International Space Station (ISS) at the end