top of page

SpaceX launches US military constellation satellites

Mission Tranche 0 will serve as the warfighter immersion tranche and support military exercises.

Falcon 9 rocket takes off from Vandenberg

SpaceX launched on Sunday, April 2, 2023, ten satellites of the Tranche 0 (zero) Transport Layer group, using the Falcon9 v1.2 FT Block 5 rocket n° B1075.2 that took off from the SLC-4E platform at 14:29 UTC (10:29 EDT | 07:29 PDT) from Vandenberg base in California. Falcon 9 headed south in azimuth to achieve a circumpolar orbit inclined 80 degrees to the equator. The first stage 'core' landed in the LZ-4 landing zone near to launch site, and the fairing shells were recovered about 490km from the coast by the vessel NRC Quest. The re-entry of the second stage wreckage occurred over the South Pacific. The mission was sponsored by the Space Development Agency (SDA), an agency of the United States Department of Defense, under its National Defense Space Architecture (NDSA). The second stage placed the satellites in an orbit of 941 x 952 km, with an inclination of 81.00°.

The launch, originally scheduled for March 30, was postponed out of an abundance of caution to investigate technical issues with the rocket. York Space Systems built eight ' transport ' satellites and SpaceX built two ' tracking ' satellites based on its Starshield chassis. To fully populate Tranche 0, York Space Systems and Lockheed Martin will each produce ten transport satellites, for a total of twenty T Zero transport satellites. SpaceX and L3Harris will each deliver four tracking satellites, for a total of eight spacecraft. Ground support for Tranche 0 is provided by the United States Naval Research Laboratory.

Falcon 9 launches the SDA Tranche 0 mission to low-Earth orbit
“This is a major achievement for the SDA and the entire Department of Defense. It shows that our main pillars, proliferation and spiral development, can contribute to national security,” said Derek Tournear, director of the SDA. “Through this release, we have demonstrated that SDA can maintain a schedule to deliver enhanced capabilities every two years. This revolutionary approach is enabled by growth in the commercial market, allowing us to move forward to provide combat capabilities in every future trench.”

It was the second attempt to launch the B1075 with Tranche zero mission. The launch was scheduled for March 30th, but canceled close to T-zero due to unspecified technical problems that caused the automatic system to cancel the takeoff. Later options, in the following days, were postponed “…to allow for additional checks”, a phrase used by SpaceX to cover up breakdowns, logistical problems or procedural abnormalities in launch preparation.



The Space Development Agency plan

The plan is that a fleet of spacecraft, each smaller (at 150 kg) and cheaper than existing missile warning satellites, will improve the Pentagon's ability to detect and track emerging threats, such as hypersonic missile strikes, and then deliver the tracking data directly to ground, air, or naval forces. using existing tactical radio networks. US and allied forces hope to be able to shoot down the enemy missile - an area in which the Americans lag behind the Russians, which have the Kh-47M Kinzhal hypersonic missile as their star. There will be Transport class satellites and four Tracking class satellites.

Combining conventional tactical radio links, laser-satellite communications, and wide-view infrared sensors, hundreds of SDA spacecraft could be launched by the end of the decade as the Pentagon ramps up efforts to counter "new threats" from its enemy nations. Precisely the first ten prototypes – eight relay spacecraft and two missile tracking platforms – will be launched on this flight.

Launch summary

The “ warfighter immersion tranche 0” system will demonstrate the feasibility of “an architecture proliferated in cost, schedule and scalability for the performance required for beyond line-of-sight targeting and advanced missile detection and tracking. ” The program foresees twenty-eight satellites (SVs, for Space Vehicles) from Tranche 0 – twenty in the Transport Layer “Transport Layer” and eight from the Tracking Layer “Tracking Layer” in two launches, the first being this March and the other in June 2023 at a cost of approximately $15 million per spacecraft.




Tranche 0 consists of a total of 28 optically connected satellites: those of “Transport” are 20, forming the mesh of the satellite communications network. These spacecraft are deployed in two configurations: Group A (SVA): 14 units in a mesh equipped with two optical communications terminals (OCTs) each and radio frequency receiving and transmitting capabilities. Group B (SVB) consists of six spacecraft, in SVA configuration, with a tactical data link (TDL) receive/transmit capability. In the “Tracking” function, eight spacecraft equipped with wide field of view (WFOV) infrared sensors and two OCTs each. The vehicles will always be distributed in two orbital planes with an inclination of 80° in the circular orbit of 950 km. This SDA constellation is expected to operate in Ka-band, have stereo coverage and be 'dynamically networked' for simpler transfers, higher bandwidth and fault tolerance. Initially, the Tranche 0 constellation is expected to have limited network capacity. Future enhancements (from Tranche 1 onwards) will significantly increase data routing over a larger satellite network. The constellation will also have the ability to integrate with Link-16 and the Integrated Broadcast System (IBS). The integration of Link-16 and IBS into the Transport Layer will modernize current capabilities to better serve warfighters' needs for worldwide threat alerts and situational awareness information across the full range of military operations. have stereo coverage and are 'dynamically networked' for simpler transfers, higher bandwidth and fault tolerance. Initially, the Tranche 0 constellation is expected to have limited network capacity. Future enhancements (from Tranche 1 onwards) will significantly increase data routing over a larger satellite network. The constellation will also have the ability to integrate with Link-16 and the Integrated Broadcast System (IBS). The integration of Link-16 and IBS into the Transport Layer will modernize current capabilities to better serve warfighters' needs for worldwide threat alerts and situational awareness information across the full range of military operations. have stereo coverage and are 'dynamically networked' for simpler transfers, higher bandwidth and fault tolerance. Initially, the Tranche 0 constellation is expected to have limited network capacity. Future enhancements (from Tranche 1 onwards) will significantly increase data routing over a larger satellite network. The constellation will also have the ability to integrate with Link-16 and the Integrated Broadcast System (IBS). The integration of Link-16 and IBS into the Transport Layer will modernize current capabilities to better serve warfighters' needs for worldwide threat alerts and situational awareness information across the full range of military operations. Constellation Tranche 0 is expected to have limited network capacity. Future enhancements (from Tranche 1 onwards) will significantly increase data routing over a larger satellite network. The constellation will also have the ability to integrate with Link-16 and the Integrated Broadcast System (IBS). The integration of Link-16 and IBS into the Transport Layer will modernize current capabilities to better serve warfighters' needs for worldwide threat alerts and situational awareness information across the full range of military operations. Constellation Tranche 0 is expected to have limited network capacity. Future enhancements (from Tranche 1 onwards) will significantly increase data routing over a larger satellite network. The constellation will also have the ability to integrate with Link-16 and the Integrated Broadcast System (IBS). The integration of Link-16 and IBS into the Transport Layer will modernize current capabilities to better serve warfighters' needs for worldwide threat alerts and situational awareness information across the full range of military operations. The constellation will also have the ability to integrate with Link-16 and the Integrated Broadcast System (IBS). The integration of Link-16 and IBS into the Transport Layer will modernize current capabilities to better serve warfighters' needs for worldwide threat alerts and situational awareness information across the full range of military operations. The constellation will also have the ability to integrate with Link-16 and the Integrated Broadcast System (IBS). The integration of Link-16 and IBS into the Transport Layer will modernize current capabilities to better serve warfighters' needs for worldwide threat alerts and situational awareness information across the full range of military operations.

According to plans, SDA will ship the “minimum viable product” (minimum operating system) to Tranche zero by summer this year, with the role of demonstrating low latency data transport capabilities for alerting and missile tracking and allowing troops to integrate PWSA capabilities into their planning for future exercises and operations (“warfighter immersion”). Warfighter immersion opportunities will occur prior to the launch of Tranche 1 in late 2024.

“It's an exciting time,” Derek Tournir, director of the agency, said on a conference call with reporters on Wednesday. “The Space Development Agency was established just over four years ago, this month, and tomorrow will be the first release of our Space Architecture Tranche 0. The “SDA Proliferated Warfighter” space architecture will consist of 28 satellites scheduled for launch this year as a 'proof of concept' for a missile tracking and data relay network, followed by more than 150 additional satellites launched in 2024 and 2025 to provide initial operational. The new early warning system will consist of a multilayer network of satellites and supporting elements that will provide global military communications and missile warning, indication and tracking capabilities in low orbit.

The SDA Transport Layer is exploring technical areas including: Optimized control of modulation techniques (including wideband or narrowband operations), simultaneous transmit and receive technologies, communications security functions (e.g., frequency hopping) , proprietary state-of-the-art waveforms, spatial deployment of tactical data links, automated dynamic networking and routing techniques, commercial cryptographic systems, Blockchain technologies, and multiband Phased Array antennas.


Terran Orbital Corporation transported ten chassis last December to Lockheed Martin in support of Tranche 0 Transport Layer. Manufacturing the chassis proved that the company could produce at a rate in excess of one per week over a period of approximately six weeks. “The delivery of all chassis marked an important milestone and we are excited to continue the effective teamwork as Terran Orbital will also design and build the chassis for Lockheed Martin's Tranche 1 Transport Layer satellites,” said co-founder and Terran President and CEO Marc Bell. “We are always excited to work with Lockheed Martin and look forward to transporting the Tranche 1 satellites.”


launch schedule

hh min ss Event

  • 00:00:00 Take off

  • 00:01:12 Max Q (maximum stress moment on the rocket)

  • 00:02:17 Cutting of the 1st stage engines (MECO)

  • 00:02:20 Second stage separation

  • 00:02:28 2nd stage engine ignition (SES-1)

  • 00:02:33 Core B1975 'boostback' ignition

  • 00:03:02 Fairing separation

  • 00:03:28 End of boostback ignition

  • 00:06:09 Start of 1st stage re-entry ignition

  • 00:06:25 Re-entry ignition completed

  • 00:07:15 Start of 1st stage landing ignition

  • 00:07:48 B1075 landing

(Second stage flight sequence is classified as per SDA request)

95 views0 comments
bottom of page