National Security Space Launch
USSF program assuring military access to space.
Last updated
National Security Space Launch (NSSL) is a United States Space Force program that assures access to space for Department of Defense and other government payloads. Managed by the Assured Access to Space Directorate of the Space Systems Command, it evolved from the Evolved Expendable Launch Vehicle program. The program oversees launches of the nation's most valuable military satellites.
Quick Facts
- Program start
- 1994
- Original name
- Evolved Expendable Launch Vehicle (EELV)
- Name change to nssl
- 1 March 2019
- Managing organization
- Assured Access to Space Directorate (SSC/AA) of the Space Force's Space Systems Command
- Partner organization
- National Reconnaissance Office
- Initial launch vehicles developed
- Boeing Delta IV and Lockheed Martin Atlas V
- Later added vehicle
- Falcon 9 (SpaceX)
Facts from the source article.
History
The United States Air Force initiated the Evolved Expendable Launch Vehicle program in 1994 after years of government-funded studies into improved systems and architecture. The program aimed to replace legacy vehicles such as Delta II, Atlas II, and Titan IV by reducing costs through standardized fairings, liquid core vehicles, upper stages, and solid rocket boosters. A Standard Payload Interface bus was also proposed to save money and improve efficiency.
Reducing launch costs and ensuring national access to space were the two main goals. National Presidential Directive Number 40 states that access to space through U.S. space transportation capabilities is essential for placing critical government assets into space, augmenting space-based capabilities in a timely manner, and supporting government and commercial human space flight. Procurement of EELV boosters was intended to evolve toward commercial practice.
Initial bids came from Lockheed Martin, Boeing, McDonnell Douglas, and Alliant Techsystems; Boeing initially proposed using the RS-25 Space Shuttle main engine. In October 1998 two initial launch services contracts (Buy 1) were awarded, totaling more than $3 billion. Boeing received a contract for 19 of 28 launches and $1.38 billion; Lockheed Martin received a contract for 9 launches and $650 million. Both companies also received $500 million each for the final development phase.
Boeing developed the Delta IV based on Common Booster Cores and the Delta Cryogenic Second Stage, while Lockheed Martin developed the Atlas V based on Common Core Boosters and the Centaur upper stage. In 2002, both Delta IV and Atlas V delivered their first payloads to orbit: the commercial satellites Eutelsat 33B and Eutelsat 8 West C, respectively.
Launch vehicles
Since 2019, four vehicles have been certified by the Department of Defense for NSSL launches: Atlas V, Delta IV Heavy, Falcon 9, and Falcon Heavy. Delta IV Medium retired in August 2019, and Delta IV Heavy retired in April 2024. After a two-year solicitation and competition process in 2018–2020, the USSF selected SpaceX (Falcon 9 and Falcon Heavy) and ULA's yet-to-be-certified Vulcan Centaur to supply military launch requirements from 2022 to 2027.
New Glenn was considered for the first time in NSSL Phase 3 Lane 1 bidding. Delta IV Medium flew with two or four solid rocket boosters on a single Common Booster Core; the Delta Cryogenic Second Stage had 4-meter and 5-meter diameter versions. The Delta IV Medium retired after the 22 August 2019 launch of a GPS-III satellite using a Delta IV M+(4,2) with two SRBs and a 4-meter fairing. Delta IV Heavy used three Common Booster Cores each powered by an RS-68A engine, a 5-meter DCSS powered by an RL10, and a 5-meter fairing.
In 2020, ULA announced retirement of the Delta IV after five more launches; the final flight occurred in April 2024. Each Atlas V uses a Common Core Booster powered by one RD-180 engine, a Centaur upper stage with one or two RL10A-4-2 engines, up to five Graphite-Epoxy Motor SRBs, and two payload fairing diameters. A three-digit naming convention indicates fairing diameter (4.2 or 5.4 meters), number of SRBs (0 to 5), and number of RL-10 engines (1 or 2).
In August 2021, ULA announced Atlas V retirement with all 29 remaining launches sold; the last NSSL launch occurred on 30 July 2024. As of August 2025, 13 launches remain, all for non-DoD customers.
More in Space Launch Vehicles of the United States
Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: National Security Space Launch (CC BY-SA 4.0).
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