Vandenberg AFB Space Launch Complex 3

Space Launch Complex 3 (SLC-3) is a launch site at Vandenberg Air Force Base that has been used by Atlas and Thor rockets. It was built in the early 1960s and consists of two pads, SLC-3E (East) and SLC-3W (West). The East-West coastline at Vandenberg allows SLC-3 to launch over-ocean polar trajectories that avoid landfall until passing over Antarctica. By contrast, Cape Canaveral has a North-South coastline permitting over-ocean launches into standard orbits.

SLC-3E
Three successful Atlas IIAS missions were flown from SLC-3E. The first mission, flown on December 18, 1999, launched the Terra satellite. The other two launched satellites in the Naval Ocean Surveillance System, USA 160 and USA 173. The final Atlas IIAS mission from SLC-3E was launched on December 2, 2003.

It was reported in 2003 that SLC-3E would be overhauled to serve as a launch platform for the Atlas V rocket after plans to build two Delta IV launch platforms were put on hold. Renovations of SLC-3E, which began after a January 2004 ground breaking ceremony, included raising the Mobile Service Tower roof by approximately 30 ft, to a height of 239 ft. The tower can thus accommodate an Atlas V 500 series vehicle with its larger payload fairing. In July 2004 Lockheed Martin announced the arrival of the fourth and final segment of the fixed launch platform (FLP). The segments had been transported from a fabrication facility in Oak Hill, FL, 3500 mi away. The largest segment weighed 90 tons and, "is thought to be the biggest over-the-road shipment ever attempted cross-country." In February 2005 the activations team handed over the launch pad to the operational team, marking the end of major reconstruction. The first Atlas V launch from SLC-3E took place at 10:02 GMT on March 13, 2008.

SLC-3W
SLC-3W was used briefly by SpaceX during the early development of the Falcon 1 launch vehicle.

Several test firings of the Falcon 1 were accomplished before SpaceX discovered that due to the overflight risk they would not be allowed to launch from SLC-3W while launch vehicles were standing on adjacent launch sites. As one of the adjacent sites was at the time occupied by a "pad queen" (a launch vehicle that sits on its launch pad for months or years before launch) the restriction caused SpaceX to abandon SLC-3W and instead develop their Omelek Island launch site for Falcon 1. SpaceX co-founder Elon Musk has stated that no compensation was paid to SpaceX over this issue.

It was announced in mid-2010 that from mid-2012 SpaceX is to use SLC-4 for Falcon 9 launches from Vandenberg.

SpaceX announced in April 2011 that they would launch the first flight of Falcon Heavy from Vandenberg SLC-4, anticipated in 2013.