The US Space Force has made a $2.29 billion deal with SpaceX for the development of a proliferated low-Earth orbit (LEO) constellation called the Space Data Network (SDN) to reinforce future American military space-based communications.

The system is expected to produce an operational prototype by the end of 2027, according to Space Systems Command.

“The SDN Backbone leverages the best of commercial innovation and delivers a strong foundation for the SDN mission set — a huge benefit and enabler for our warfighters,” Col. Ryan Frazier, acting Space Force portfolio acquisition executive for space-based sensing and targeting, said in a statement.

SpaceX’s “Starshield” offering, serving US and allied governments, builds on Starlink technology to deliver optical and radio reconnaissance, early missile warning, and target tracking. COO Gwynne Shotwell has previously implied that SpaceX is not allowed to disclose much information about Starshield.

The Space Force also recently awarded Viasat and SES contracts worth a combined $437.6 million to build a small geostationary (GEO) X-band and military Ka-band military communication satellite network designed to withstand jamming and cyber threats, as part of the Protected Tactical Satcom-Global (PTS-G) program.

The first batch, referred to as “Swarm 1,” comprises four satellites, with each company responsible for two, and is scheduled for delivery in March 2029.

“Our dual-band X/Ka-band design, combined with Viasat’s extensive understanding of capacity economics, maneuverable GEO architectures, and heritage of delivering secure communication solutions to Department of War users, will provide critical capabilities to enable global connectivity and enhance warfighters’ situational awareness and operational effectiveness to meet emerging threats,” John Reeves, vice president of Space and Mission Systems, Viasat Government, said in a statement.

Viasat and SES were chosen from a shortlist of five drawn up in July to develop demonstration payloads for PTS-G, which included Astranis, Boeing, and Northrop Grumman.

Transport layers

The SDN backbone with Starlink will be expected to provide data transport, tactical communications, and satellite broadband to joint armed forces, particularly on major Pentagon projects like Golden Dome and the scary new acronym CJADC2, combined joint all-domain command and control. The Pentagon said it has established a consortium of industry partners working on the technical challenges and integration of the SDN.

“Our acquisition strategy is designed to foster competition and broaden our industrial base,” Lt. Col. Jeffrey Fry, SDN Backbone system program manager, said in a statement. “We aren’t trading speed for scale; we are demanding both. By using rapid prototyping and Other Transaction Authorities, we are ensuring our advanced solutions are integrated and delivered to the warfighter as fast as possible.”

The news reclassifies SDN Backbone from its prior classification, MILNET, a program to field a satcom constellation for the Space Force and National Reconnaissance Office. Additionally, the SDN Backbone program, if approved by Congress, will comprise Tranche 3 of the existing Transport Layer program from the Space Development Agency, a program that the agency was all but founded by DARPA to develop in 2018.

DARPA (the Defense Advanced Research Projects Agency) also initiated the Blackjack constellation program in 2017, which possessed very similar goals to the SDN Backbone – establishing tactical communications by satellite through commercial contracts. Developed by Lockheed Martin and launched by SpaceX, the first four Blackjack satellites flew in June 2023.

The US Space Force awarded an additional $30m contract to Parsons Corporation in 2025 to expand the program.