SpaceX successfully launched 21 satellites into low Earth orbit (LEO) on September 10, 2025, for the U.S. Space Development Agency's (SDA) Tranche 1 Transport Layer mission. The launch occurred at 7:12 a.m. PT from Vandenberg Space Force Base in California, marking a significant step in enhancing the U.S. military's satellite communication capabilities.
The Falcon 9 rocket's first stage, booster B1093, completed its sixth flight and successfully landed on the 'Of Course I Still Love You' drone ship. This mission is part of the SDA's Proliferated Warfighter Space Architecture (PWSA), a network designed to provide global communication access and persistent, encrypted regional connectivity for military operations worldwide. The PWSA aims to comprise hundreds of small satellites in LEO.
These 21 satellites were manufactured by York Space Systems, a Denver-based company. York, along with Northrop Grumman and Lockheed Martin, is contracted by the SDA to produce 42 satellites each for this initial tranche. This launch represents the first operational deployment for the PWSA's Tranche 1 program, which will offer capabilities such as Link-16, Ka-bands, and optical downlinks for space-based data transport.
The SDA, established in March 2019, focuses on rapidly developing and deploying cost-effective space-based assets for the Department of Defense. The Tranche 1 Transport Layer is the agency's first operational network, with plans to refresh the constellation every two years through new tranche launches. The satellites are expected to provide initial warfighting capabilities, including regional persistence for tactical military data channels, advanced missile tracking, and beyond-line-of-sight targeting, starting in 2027.
The SDA's development model incorporates new technology every two years to continuously improve coverage and capabilities. The agency has a history of collaboration with York Space Systems, having previously awarded contracts for Tranche 0 and experimental systems. The complete Tranche 1 constellation is planned to include 154 satellites, with 126 for the Transport Layer and 28 for the Tracking Layer, plus four missile defense demonstration vehicles. The SDA anticipates launching approximately one mission per month to finalize the Tranche 1 constellation.