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Space Launch Complex 6
First launch of a Boeing Delta IV Medium+ (4,2) from SLC-6 on June 27, 2006 (Official photo by Thom Baur for Boeing)
Launch site Vandenberg AFB
Location 34.5813 N
120.6266 W
Short name SLC-6
Operator US Air Force
Total launches 6
Launch pad(s) 1
Minimum / maximum orbital inclination 51° - 145°
Launch history
Status Active
First launch Athena-1, 15 August 1995
Last launch DMSP-5D3 F-17, 4 November 2006
Associated rockets Titan III
Space Shuttle
Delta IV (current)

Space Launch Complex-6 (SLC-6, nicknamed "Slick Six") at Vandenberg Air Force Base in California is a launch pad and support area. It was originally designed for the launching of the Titan III in support of the cancelled Manned Orbiting Laboratory, and was later rebuilt for the Space Shuttle, which also never used it due to budget, safety and political considerations. It was subsequently used briefly by Athena rockets, before being remodified to support the Delta IV family of unmanned launchers, which have used the pad since 2006. Launches from SLC-6 fly southward into a polar orbit, not eastward as were typical launches from Florida.

Since polar orbits can allow full global coverage on a regular basis, they are often used for earth-mapping-, earth observation- and reconnaissance satellites, as well as some weather satellites. However, polar orbits require more energy than a typical eastward launch, as they do not benefit 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.



SLC-6, part of Vandenberg's "South Base," was originally part of the Sudden Ranch, prior to its purchase by the U.S. Air Force in the mid-1960s under the law of eminent domain. In addition to the ranch, the Point Arguello lighthouse was based there, which has since then been replaced by an off-shore LORAN tracker. With the purchase of the base, the Air Force started construction of the SLC-6 facility on March 12, 1966 to support launches of a modified Titan III for the Manned Orbiting Laboratory (MOL). After significant construction work was completed, the MOL program was cancelled on June 10, 1969, so further work on SLC-6 stopped as the facility was placed in mothball status.

Vandenberg's Space Launch Complex Six (SLC-6) under construction, March 1966.

With plans of launching civilian and military equatorial space shuttle flights from Kennedy Space Center (KSC) and military polar orbit flights from Vandenberg, NASA and the Air Force looked at different sites for launching the shuttle, finally deciding upon SLC-6, due to its dedicated manned spaceflight role that was leftover from the canceled MOL program.

In 1972, Vandenberg AFB was chosen as the western launch site for Air Force shuttle launches. Use of SLC-6 was approved in 1975, and re-construction of the former MOL launch facility occurred between January 1979 and July 1986 as SLC-6 was rebuilt to accommodate the space shuttle.

There were several reasons for using SLC-6:

  • Florida shuttle launches to polar orbit would have entailed a large payload penalty;
  • Florida shuttle launches to polar orbit would necessitate overflying South Carolina, and the External Tank would be jettisoned and overfly Canada and Russia, and
  • Use of the existing and partially constructed Titan III facilities at SLC-6 would reduce building costs for the shuttle launch complex.
Space Launch Complex Six (SLC-6) in 1980.

A Senate report summarized: "The Air Force originally justified the expenditure of such SLC-6 funding on the basis of a need to launch high-priority military payloads into polar orbits. After Defense Department officials testified that polar orbits could not be achieved by launching from Kennedy Space Center in Florida, the Congress initiated construction of... SLC-6."

There were significant layout differences between the shuttle launch complexes at KSC and SLC-6 at Vandenberg. KSC had the Orbiter Processing Facility, Shuttle Runway facility, Mate-Demate Device (for loading the Orbiter on the Shuttle Carrier Aircraft), the Vehicle Assembly Building, and Launch Complex 39. SLC-6 consolidated the VAB (stacking) and LC-39 (launching) functions, while a processing facility, located at North Base, handled the vehicle processing, along with providing a Mate-Demate Device, and a 13,000 ft (4,000 m) runway for Shuttle landings.

Space Shuttle

Enterprise at SLC-6 in launch configuration in October 1985. (Official USAF photo, TSgt James Pearson, 1369th Audiovisual Squadron)

Over $4 billion were spent on the new space shuttle modifications. The original Mobile Service Tower (MST) was lowered in height and two new flame ducts were added for the shuttle's Solid Rocket Boosters. Additional modifications or improvements included liquid hydrogen and liquid oxygen storage tanks, a payload preparation room, payload changeout room, a new launch tower with escape system for the shuttle crewmembers, sound suppression system and water reclamation area and a Shuttle Assembly Building were added to the original complex.

Additionally, the existing 5,500-foot (1,700 m) runway and overruns on the North Base flightline were lengthened to nearly three miles (15,000 ft) to accommodate end-of-mission landings. Turn-around servicing and refurbishing of the orbiter would be accomplished in the adjacent Orbiter Maintenance and Processing Facility (OMPF).

SLC-6 was declared operational during acceptance ceremonies held on October 15, 1985. However, much additional work and testing was still required. Enterprise was used for a series of fit checks like those conducted at LC-39 in 1980.

The inaugural polar-orbit flight, designated STS-62-A, and using Discovery with Shuttle veteran Robert Crippen as commander, was planned for October 15, 1986. However, the Challenger Disaster of January 28, 1986 grounded the Shuttle fleet as efforts were concentrated on recovery and returning the program to flight after a two year hiatus.

On July 31, 1986 Secretary of the Air Force Edward C. Aldridge Jr., announced that Vandenberg's space shuttle program would be placed in "operational caretaker status," six months after the space shuttle Challenger accident. A few months later, however, SLC-6 was placed in "minimum caretaker status" on February 20, 1987.

Eventually, on May 13, 1988, Secretary Aldridge then directed the Air Force to transfer space shuttle assets at Vandenberg to other organizations (specifically, the Kennedy Space Center) by September 30, 1989, the end of the fiscal year. The work was completed 10 days early on September 20, 1989 when SLC-6 was placed in mothball status.

Several factors accounted for this:

  • The Challenger disaster highlighted that sole dependency on the shuttle was unwise;
  • SLC-6 would have generated more contaminated waste water than originally envisioned, necessitating an expensive treatment plant;
  • Further study showed more sound suppression water would have been needed, requiring upgraded water supply facilities;
  • Vehicle icing would have been more problematic than in Florida, and it was unclear how well SLC-6 facilities would handle that;
  • Blast protection of nearby occupied buildings was unsatisfactory and more construction would have been required to safeguard them;
  • Post-Challenger, the more confined SLC-6 launch area raised concerns of entrapped gaseous hydrogen causing a fire or explosion;
  • Large construction cost overruns, and
  • Independent audits found significant construction quality problems which would have been expensive to fix.

The Air Force officially terminated the space shuttle program at Vandenberg on December 26, 1989. The estimated cost for the failed program was $4 billion.

Just six months later on July 6, 1990, Lockheed Space Operations Company (LSOC) was awarded an Air Force ground system contract to modify SLC-6 into a Titan IV/Centaur launch complex — essentially an uprated facility from the original MOL program that would have launched a Titan III vehicle. Site work was scheduled to begin in late-FY1992, and lead to an initial launch capability sometime in FY1996.

However, on March 22, 1991, HQ USAF reversed itself again by announcing the termination of the Titan IV/Centaur program at SLC-6. The reasons given for the project being canceled was due to "insufficient Titan IV launch requirements from the West Coast to support the construction of a new launch pad.". The contract with LSOC was closed out several months later.


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.

Nevertheless, the utilization of SLC-6 was far from over. In the early 1990s, Lockheed 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.

Lockheed-Martin's Athena 1 (LLV 1) sits atop a "milkstool" platform at SLC-6, August 1997. (Official USAF photo)

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.

Aerial view of SLC-6 as it looks today. (Photo: U.S. Air Force and Boeing)

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 rocket 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.

Some 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 M/V Delta Mariner cargo vessel that docks just south of SLC-6 at the same location originally constructed for receiving and offloading space shuttle external tanks.

Delta IV

Boeing Delta IV Medium+ (4,2) lifts off from SLC-6. (U.S. Air Force photo/Staff Sgt. Quinton Russ, 30th Communications Squadron)

Boeing developed the Delta IV class of vehicles as its entrant in the Department of Defense's Evolved Expendable Launch Vehicle (EELV) program. The main objective of EELV is aimed at cutting launch costs and simplifying the process of getting satellites into space. Boeing's main competitor, Lockheed Martin, has a similar class of vehicles known as the Atlas V that made its West Coast debut in early March 2008, flying from the modified Space Launch Complex-3 East on South Base.

After sitting on the pad since late-2003 and enduring technical issues with both the booster and the payload, the first of the Delta IV launch vehicles to fly from SLC-6 successfully lifted off at 8:33 p.m. PDT on June 27, 2006.

The Delta IV Medium+ (4,2) rocket lofted NROL-22, a classified satellite for the National Reconnaissance Office, into orbit. The payload was successfully deployed approximately 54 minutes later.

This first Delta IV launch from Vandenberg is an important achievement for Boeing and our NRO and Air Force customers. Today we successfully validated launching the Delta IV from SLC-6, providing the Air Force and the nation with the first operational West Coast launch site for the EELV program. With this launch, the Delta team has fulfilled all the EELV requirements outlined by the Air Force. We have a full family of launch vehicles, including a flight-proven, heavy-lift vehicle, a domestically produced first stage engine and now fully operational launch sites on both coasts.
-- Dan Collins, vice president of Boeing Launch Systems

According to a post-launch Boeing News press release, the mission was the first for the NRO aboard a Delta IV and the second aboard a Delta rocket. The first was the GeoLITE mission in 2001 aboard a Delta II.

Another Delta IV Medium vehicle flew a mission for the Air Force Defense Meteorological Satellite Program, orbiting DMSP-17, 4 November, 2006.


34°34′53″N 120°37′35″W / 34.58139°N 120.62639°W / 34.58139; -120.62639Coordinates: 34°34′53″N 120°37′35″W / 34.58139°N 120.62639°W / 34.58139; -120.62639



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