With Second Delay, SpaceX’s SDA Tranche 0 Launch Is Expected Saturday Morning

SpaceX announced earlier this morning (September 1) that the planned launch of 13 observation and communication satellites for the Space Development Agency (SDA) on a Falcon 9 rocket into a polar orbit has been delayed until Saturday, September 2 at the earliest. 

This is the second delay for the launch, after a planned launch on August 31st was scrubbed due to engine issues, according to CBS News’s William Harwood. The reason for today’s scrub was unspecified.

The SDA is the US military’s “constructive disruptor for space,” born of an attempt to sidestep traditionally slow military procurement and provide the same kind of rapid deployment of space-based assets now seen in the private sector. It was started in 2019, and was then folded into the United States Space Force (USSF) in 2022.

The delayed launch is part of the SDA’s Proliferated Warfighter Space Architecture (PWSA) program, formerly known as the National Defense Space Architecture. PWSA is intended to be a constellation of LEO satellites aimed at supporting US military efforts to track hostile missile launches in much the same way that the military’s existing geosynchronous (GEO) and Medium Earth Orbit (MEO) satellites do. 

According to a Department of Defense quote in previous SpaceRef coverage, PWSA will eventually support “beyond line-of-sight targeting for ground and maritime time-sensitive targets.” The constellation will, the Defense Department said, “provide the ability to detect those targets, track them, calculate a fire control solution and then deliver that solution down to a weapons platform so that the target can be destroyed.” Part of the capability will be “for enemy missiles already in flight.”

The SDA’s site also describes it as a “proliferated LEO,” using redundant mesh networks of large satellite constellations to ensure that capabilities are “not compromised by disruption or defeat of a small number of assets”, reminiscent of DARPA’s original design for the Internet.

The satellite launches are split into a series of “Tranches”; each tranche being a discrete set of satellites built by several private sector contractors. The intent is that the capabilities of the overall constellation will improve with subsequent tranches, much as they do between generations of satellites in private-sector constellations like Starlink. That private-sector-style approach extends to procurement, with each Tranche providing new opportunities for vendors to compete for contracts to provide capabilities and components for the satellites. For example, the upcoming launch will be for Tranche 0, while the SDA recently signed contracts to procure Tranche 2 satellites.

Tranche 0 is a technology demonstration. It will, according to the SDA, demonstrate the “minimum viable product,“ and the “feasibility of the proliferated architecture in cost, schedule, and scalability towards necessary performance for beyond line of sight targeting and advanced missile detection and tracking.” Tranche 0 features a mix of 20 Transport Layer space vehicles (SVs) with both optical and RF-based communications capabilities, and 8 Tracking Layer SVs with optical comms and sensor payloads. Future tranches will add more satellites and more “warfighting capability.”

The first 10 satellites in Tranche 0 were launched in April into a polar orbit on a SpaceX Falcon 9. While all 18 remaining Tranche 0 satellites were originally going to be launched in this mission, only 13 were included and some of the remaining satellites will now be flying on a separate mission planned by the Missile Defense Agency. 

The satellites on this mission include 10 Transport Layer satellites made by Lockheed Martin, 2 Tracking Layer satellites by SpaceX, and one Transport Layer by York Space Systems.