SpaceX Falcon 9 rocket lifts 13 military satellites to orbit

To do this, the SDA is building a space data network called the Proliferated Warfighter Space Architecture, which is made up of a transport layer and a missile-tracking sensor layer.

The Tranche 0 mission had originally been scheduled for August 31, but it was delayed due to an issue with one of the Merlin engines attached to the Falcon 9's first stage that was detected during the countdown to launch.

A second launch attempt on September 1 was also scrubbed minutes before T-0 when an issue was discovered with a valve on ground support equipment.

Falcon 9 launches @SemperCitiusSDA’s second Tranche 0 mission and the first stage returns to Earth, completing SpaceX’s 61st mission of 2023 and matching our total number of launches last year pic.twitter.com/VHFamcuIpH

— SpaceX (@SpaceX) September 2, 2023

The launch did go ahead as planned on September 2, though, and the Falcon 9 rocket's booster separated from the second stage approximately two and a half minutes into the mission.

The booster then went on to perform three engine burns, allowing it to return to Landin Zone 4 at Vandenberg roughly eight minutes after launch for one of SpaceX's iconic Falcon 9 booster landings.

The 13 spacecraft launched as part of the Tranche 0 constellation on Saturday included 11 communications satellites, 10 of which were built by Lockheed Martin and one by York Space, as well as two missile-tracking sensor satellites made by SpaceX.

A record year for Falcon 9 launches

Due to the secretive nature of the Tranche 0 mission, SpaceX showed the booster landing but then cut off its live webcast of the launch shortly afterward. It did not provide footage of the second stage flying toward orbit and did not provide payload updates.

However, shortly after the launch, SpaceX CEO Elon Musk wrote on X, formerly Twitter: "Great work by the SpaceX team successfully launching 61 Falcon rocket missions this year!"

"If tomorrow’s mission goes well, we will exceed last year's flight count," Musk added. "SpaceX has delivered ~80% of all Earth payload mass to orbit in 2023. China is ~10% & rest of world other ~10%."

Musk was referring to a Starlink satellite launch, which was successfully launched, meaning SpaceX has now launched more Falcon 9 launches than last year, making it a record year. The first-stage booster used for the Tranche 0 mission completed its 13th flight.

The two Tranche 0 missions launched by SpaceX so far were performed under a $150 million SDA contract awarded to SpaceX in December 2020. SpaceX is also scheduled to launch four more Tranche 0 missile-tracking satellites made by L3Harris later this year.