Vandenberg Space Launch Complex 4

The first launch from PALC2-4 occurred on 14 August 1964, when a KH-7 satellite was launched by an Atlas-Agena D. After 27 Atlas-Agena launches, the last of which was on 4 June 1967, the complex was deactivated.[4]

Titan IIID launch from SLC-4E

During 1971 the complex was reactivated and refurbished for use by the Martin Marietta Titan III launch vehicles. The Titan IIID made its maiden flight from SLC-4E on 15 June 1971, launching the first KH-9 Hexagon satellite.[5] The first KH-11 Kennan satellite was launched from the complex on 19 December 1976.[6] All 22 Titan IIIDs were launched from SLC-4E, with the last occurring on 17 November 1982.

The complex was then refurbished to accommodate the Martin Marietta Titan 34D. Seven Titan 34Ds were launched between 20 June 1983, and 6 November 1988. SLC-4E hosted one of the most dramatic launch accidents in US history when a Titan 34D-9 carrying a KH-9 photoreconnaissance satellite exploded a few hundred feet above the pad on 18 April 1986. The enormous blast showered the launch complex with debris and toxic propellant (hydrazine and dinitrogen tetroxide), resulting in extensive damage. 16 months after the accident, the pad was back in commission when it hosted a successful launch of a KH-11 satellite.[7][8]

Final Titan IV launch from SLC-4E in 2005

The last Titan variant to use the complex was the Titan IV, starting on 8 March 1991, with the launch of Lacrosse 2. On 19 October 2005, the last flight of a Titan rocket occurred, when a Titan IVB was launched from SLC-4E, with an Improved Crystal satellite. Following this launch, the complex was deactivated, having been used for 68 launches.

Inaugural mission of the Falcon 9 v1.1 from SLC-4E in September 2013

SpaceX refurbished SLC–4E for Falcon 9 launches in a 24-month process that began in early 2011.[2] The draft environmental impact assessment with a finding of "no significant impact" was published in February 2011.[2] Demolition began on the pad's fixed and mobile service towers in summer 2011.[3]

By late 2012, SpaceX anticipated that the initial launch from the Vandenberg pad would be in 2013, with the larger variant Falcon 9 v1.1.[9] As the pad was nearing completion in February 2013, the first launch was scheduled for summer 2013,[10] but was delayed until September 2013.

The first launch to use what is now SLC-4 occurred on 12 July 1963, when an Atlas LV-3 Agena-D launched the first KH-7 Gambit reconnaissance satellite, from PALC-2-3. Twelve Atlas-Agenas launches were conducted from PALC-2-3, with the last occurring on 12 March 1965.

Following this, it was rebuilt as SLC-4W, a Titan launch complex. The first Titan launch from SLC-4W was a Titan IIIB, on 29 July 1966. All 68 Titan IIIB launches occurred from SLC-4W, with the last on 12 February 1987.

A Titan 23G on SLC-4W

After the retirement of the Titan IIIB, it became a Titan 23G launch site, and twelve Titan II launches, using the 23G orbital configuration, were conducted between 5 September 1988 and 18 October 2003. Following the retirement of the Titan 23G, SLC-4W was deactivated. 93 rockets were launched from SLC-4W.

SLC-4W was the site of the launch of Clementine, the only spacecraft to be launched from Vandenberg to the Moon, which was launched by a Titan 23G on 25 January 1994.

SpaceX signed a five-year lease of Launch Complex 4W in February 2015, in order to use the area to land reusable launch vehicles at the pad. The location is being used for vertical landing of Return-To-Launch-Site (RTLS) first-stage boosters of the Falcon 9 rockets that are launched from the adjacent SLC-4E launch pad.[31][32] This novel use of SLC-4W had initially surfaced in July 2014 when NASASpaceFlight.com published that SpaceX was considering leasing SLC-4W for use as a RTLS vertical-landing facility for reusable first-stage boosters.[33]

Principal structures on the pad were demolished in September 2014 as construction of the landing pad began and was completed sometime around 2017.[34]

For landings at sea, see Autonomous spaceport drone ship

SpaceX has perfected RTLS landings on two landing pads that it has built at Cape Canaveral Space Force Station.[32][35] It was initially thought that the booster used to launch a fourth batch of ten Iridium NEXT satellites in December 2017 would be the first to land at Vandenberg AFB [16] but this mission was ultimately performed in expendable mode.[36] In July 2018, SpaceX applied for a permit to the Federal Communications Commission (FCC) for post-landing communications with a first stage of a Falcon 9 rocket at SLC-4W, pointing to a possible landing sometime in September 2018, possibly for the SAOCOM 1A mission[37] although this was later rescheduled for 8 October 2018 (UTC). A few weeks prior to this first landing attempt it was known to the public, again via FCC permits and also public warnings about sonic booms in the area, that SpaceX had renamed this pad as Landing Zone 4.[31] Finally, this pad was first used for a rocket booster landing of a first stage of a Falcon 9 launch vehicle in October 2018, recovering the booster that had just launched the Argentinian SAOCOM 1A satellite.[31]

Date/Time (UTC)	Rocket body	Launch Site	Trajectory	Payload	Result	Remarks	Image
8 October 2018	Falcon 9 B5 first stage booster B1048.2	SLC-4E	SSO	SAOCOM 1A	Success	First landing at LZ-4
12 June 2019	Falcon 9 B5 first stage booster B1051.2	SLC-4E	SSO	RADARSAT Constellation	Success
21 November 2020	Falcon 9 B5 first stage booster B1063.1	SLC-4E	SSO	Sentinel-6 Michael Freilich	Success
2 February 2022	Falcon 9 B5 first stage booster B1071.1	SLC-4E	SSO	NROL-87	Success
17 April 2022	Falcon 9 B5 first stage booster B1071.2	SLC-4E	LEO	NROL-85	Success
18 June 2022	Falcon 9 B5 first stage booster B1071.3	SLC-4E	SSO	SARah 1	Success
16 December 2022	Falcon 9 B5 first stage booster B1071.6	SLC-4E	Polar Orbit (PO)	SWOT	Success
30 December 2022	Falcon 9 B5 first stage booster B1061.11	SLC-4E	LEO	EROS-C3	Success
2 April 2023	Falcon 9 B5 first stage booster B1075.2	SLC-4E	Polar Orbit (PO)	SDA Tranche 0A	Success
15 April 2023	Falcon 9 B5 first stage booster B1063.10	SLC-4E	SSO	Transporter 7	Success
12 June 2023	Falcon 9 B5 first stage booster B1071.9	SLC-4E	SSO	Transporter 8	Success
2 September 2023	Falcon 9 B5 first stage booster B1063.13	SLC-4E	Polar Orbit (PO)	SDA Tranche 0B	Success
December 2023	Falcon 9 B5 first stage booster B10??.?	SLC-4E	SSO	SARah 2 & 3	Planned
December 2023	Falcon 9 B5 first stage booster B10??.?	SLC-4E	SSO	WorldView Legion 1 & 2 (2 Sats)	Planned