SpaceX launches 21 satellites to orbit for the US military after 5-day delay (video)

SpaceX just sent another batch of satellites to orbit for the U.S. military.A Falcon 9 rocket lifted off from California's Vandenberg Space Force Base today (Oct. 10) at 3:39 a.m. EDT (0739 GMT; 12:39 a.m. local time), hauling 21 "data transport" satellites to orbit for the U.S. Space Force's Space Development Agency (SDA). That was five days later than originally planned. SpaceX tried to launch the mission on Monday (Oct. 5), but the Falcon 9 aborted that attempt in the countdown's final minute, for reasons that the company has not disclosed.The Falcon 9's first stage comes down for a landing at Vandenberg on Oct. 10, 2026. (Image credit: SpaceX)Today's launch helps build out the SDA's Proliferated Warfighter Space Architecture (PWSA), which SpaceX describes as "a mesh network of optically connected satellites in low Earth orbit [LEO] that enable global military tactical communications and missile warning, indication and tracking capabilities."The liftoff was the fourth of nine that SpaceX will conduct to help assemble the architecture's Tranche 1 — the "initial warfighting capability tranche," according to the SDA.Tranche 1 will eventually consist of 154 operational satellites in LEO — 126 data-transport spacecraft and 28 missile-tracking vehicles. There will also be four missile-defense test satellites, which will sport a "higher fidelity" infrared sensor than their tracking counterparts, SDA officials wrote. (Missile-tracking satellites generally hunt for the heat signatures these weapons produce during flight).Eighty-four of the 126 data-transport satellites have now launched to date, all of them on Falcon 9s, which lifted off from Vandenberg in September 2025, October 2025, July of this year and today.And, as its name suggests, Tranche 1 will be just the beginning, if all goes according to plan."SDA leverages spiral development to deploy and proliferate new capability into a new generation of the PWSA every two years, called a 'tranche,' to continually increase capability used by the warfighter," SDA officials wrote in a Tranche 1 fact sheet.Previous Booster 1103 launchesNROL-179 | SDA-T1TL-E | 3 Starlink missionsEverything seemed to go well on today's launch. The Falcon 9's first stage came back to Vandenberg for a landing a little over seven minutes after liftoff. It was the sixth mission for this particular booster, which is designated 1103. Its most recent flight was the July Tranche 1 mission for the SDA.SpaceX ended its webcast shortly after booster touchdown, at the request of the SDA, so we did not get to see satellite deployment. But that's the norm for national security launches.The satellites were successfully deployed in their target orbit, according to an Oct. 10 announcement by their builder, aerospace giant Northrop Grumman. The 21 spacecraft "will provide secure, resilient, low-latency communications and data transport in low Earth orbit," helping to connect warfighters with missile-tracking satellites, the company wrote.Today's mission was the 111th Falcon 9 flight of the year. The vast majority of these — more than 70% — have helped build out SpaceX's Starlink broadband megaconstellation, which currently consists of more than 11,000 satellites.Editor's note: This story was updated at 12:45 p.m. ET on Oct. 10 with news of successful satellite deployment.