SpaceX sent another batch of satellites to orbit for the U.S. military early Saturday, launching 21 data-transport spacecraft for the Space Force's Space Development Agency after a five-day delay.
A Falcon 9 rocket lifted off from Space Launch Complex 4 East at Vandenberg Space Force Base in California at 3:39 a.m. EDT, hauling the Northrop Grumman-built satellites into low Earth orbit. The satellites were successfully deployed, Northrop Grumman confirmed.
The launch was five days late. SpaceX tried to fly the mission on Monday, October 5, but the Falcon 9's automated systems halted the countdown in the final minute. The company has not disclosed the reason for the abort.
Saturday's mission was the fourth of nine Tranche 1 launches SpaceX will fly for the SDA — and it brought the number of data-transport satellites now in orbit to 84 of the 126 planned. The full Tranche 1 constellation will eventually number 154 operational satellites: 126 for data transport and 28 for missile tracking, plus four missile-defense test vehicles carrying higher-fidelity infrared sensors.
The satellites are building blocks of the Proliferated Warfighter Space Architecture — a mesh network of optically linked spacecraft designed to give U.S. forces resilient, low-latency tactical communications and missile warning, tracking and targeting from orbit. The idea is strength in numbers: spreading capabilities across many satellites instead of a few big, vulnerable ones.
The mission also showed off SpaceX's reusability. About seven and a half minutes after liftoff, the Falcon 9's first stage — booster B1103, on its sixth flight — touched down back at Vandenberg's Landing Zone 4. Its previous missions included another SDA launch in July and the NROL-179 national security flight.
SpaceX ended its webcast shortly after the booster landing at the SDA's request — standard practice for national security launches, where the payload deployment happens off-camera.
Tranche 1 is meant to deliver an "initial warfighting capability" beginning in 2027: persistent tactical data links, missile tracking and warning, beyond-line-of-sight targeting and battlefield connectivity. And as the name suggests, Tranche 1 is only the start — the SDA plans a new, more capable tranche every two years.
Saturday's flight was the 111th Falcon 9 launch of the year. More than 70 percent of them have gone to building out Starlink, now over 11,000 satellites strong.