| Unit Name: | 4th Space Launch Squadron |
| Dates: | 1994-1998; 2003-2019 |
| Role: | Space Launch |
| Command Structure: | Air Force Space Command |
| Garrison: | Vandenberg AFB, California |
| Decorations: | Air Force Outstanding Unit Award[1] |
| Identification Symbol Label: | 4th Space Launch Squadron emblem (approved 31 March 1995) |
The United States Air Force's 4th Space Launch Squadron was a space launch unit located at Vandenberg Air Force Base, California. It was active at Vandenberg from 1994 to 1998 and again from 2003 to 2019. It launched various satellites into orbit from the complex of launch pads at Vandenberg.
The 4th Space Launch Squadron was the Air Force's Evolved Expendable Launch Vehicle (EELV) launch agency for the West Coast. The EELV system is a liquid-fueled first stage Common Booster Core (CBC) that can be used alone, with strap-on solid fuel rocket boosters, or as a configuration of three CBCs acting as a more powerful booster.[2]
The squadron was activated at Vandenberg Air Force Base, California on 15 April 1994. Until it was inactivated in June 1998, it launched surveillance and meteorological satellites into polar orbit.[1]
After reactivation in 2003, the squadron managed operations for EELVs.[1] The EELV program was intended to develop provide alternatives to older and expensive heavy-lift launch vehicles, such as the Titan IV. EELVs include:
The Boeing Delta IV. There are different configurations for the Delta IV, which can lift payloads from 9,000 lb to over 13,000 lb into Geosynchronous Orbit.
The Lockheed Martin Atlas V. This system also has different available configurations, and can lift payloads between 10,000 lb and 30,000 lb to Geosynchronous Transfer Orbit.
The Delta II, a heritage vehicle smaller than the newer Delta IV. The Delta II can have up to nine external rockets strapped to its main stage, increasing lift capability. It can send approximately 4,000 lb into Geosynchronous Transfer Orbit.[2]
Activated on 15 April 1994
Inactivated on 29 June 1998
Activated on 1 December 2003[1]
Inactivated on 31 May 2019 (in merger with 1st Air and Space Test Squadron as 2nd Space Launch Squadron)