Space Launch Complex-6 (SLC-6, nicknamed "Slick Six") at Vandenberg Air Force Base in California was a launch pad and support area designed for the launching of the Titan III in support of the cancelled Manned Orbiting Laboratory and later for the Space Shuttle, which it was never used for, due to budget and political considerations.

It has since been remodified to support the Delta IV family of unmanned launchers. Launches from SLC-6 fly southward into a polar orbit, not eastward as were typical launches from Florida.

Polar orbits are required for many spy satellites, since it allows for covering all global areas of the planet every 24 hours on a regular basis. However, polar orbits require more energy than a typical eastward launch, due to not benefiting from the earth's rotational speed. Achieving a polar orbit from a Florida launch site is possible, but because Kennedy Space Center has major population centers to both the north and south, polar orbit flights must fly a "dog leg" route, greatly reducing payload capacity due to the extra propellant required.

Since the shutdown of SLC-6 for the shuttle program, the U.S. Air Force reverted to flying military polar orbit satellites using the Titan 34D and later Titan IV rockets.

However, the utilization of SLC-6 was far from over. In the early 1990s, Lockheed Missiles and Space Corporation began studies on the prospect of a new family of small launch vehicles for commercial and other users. Lockheed eventually approved the development of the Lockheed Launch Vehicle (LLV) program in January 1993. After the merger of Lockheed with Martin Marietta, the renamed Lockheed-Martin Launch Vehicle (LMLV) eventually would take on the moniker of Athena.



After another contract was issued in 1994 by the Air Force, modification work began on the existing SLC-6 shuttle launch mount for a small "milkstool" platform to be located over one of the two exhaust ducts originally intended for one of the large solid rocket boosters. The first operational launch from SLC-6 occurred on August 15, 1995 involving the Lockheed-Martin Launch Vehicle I (LMLV-1). Unfortunately, LMLV-1 was terminated in mid-flight after uncontrolled oscillations of the rocket were detected. This resulted in the loss of the vehicle and the payload. The cause of the mishap was later determined to be a guidance system failure coupled with overheating of the booster's first stage steering mechanism. The payload on board was GEMstar 1, a small communications satellite manufactured by CTA, Inc. for the Volunteers in Technical Assistance (VITA), a non-profit organization.

After some hardware redesign and testing, a newly rechristened Athena I successfully launched NASA's Lewis satellite into orbit from SLC-6 on August 22, 1997. Part of NASA's Small Spacecraft Technology Initiative (SSTI) and "Mission to Planet Earth" program, the $64.8 million satellite carried instruments to monitor pollution, the state of endangered-species habitats, soil resources, and the environmental impacts of energy pipelines. Designed to last three years, Lewis' thrusters misfired just four days after launch and went into a slow spin, its solar arrays unable to collect enough energy from the sun to charge its batteries. Within a month, it destroyed itself upon re-entry into the earth's atmosphere.



Another launch, on September 24, 1999 was successful as an Ikonos satellite operated by Space Imaging (later acquired by ORBIMAGE to form GeoEye) was successfully placed into a polar orbit using an Athena 2 booster.

However, with the advent of the Delta IV and Atlas V launch vehicles in the late 1990s, The Boeing Company received a lease from the Air Force on September 1, 1999 to modify SLC-6 once again to launch Boeing's Delta IV rocket family.

Most of the Shuttle-specific components at SLC-6 were removed, such as the mobile Payload Changeout Room, but the Assembly Building, Mobile Service Tower, Launch Tower, flame deflection trenches and sound suppression system and some other shuttle-oriented equipment were retained and made compatible for the new Delta IV rocket. The launch vehicle's Common Booster Core and associated flight hardware is transported from the Boeing factory in Decatur, Ala., to Vandenberg via the Delta Mariner ship that docks just south of SLC-6 at the same location originally constructed for receiving and offloading space shuttle external tanks.