ABGEBROCHEN - SpaceX - Falcon 9 - Tranche 1 Transport Layer A - SLC-4E - VSFB, Kalifornien - Spac...
Video from the channel SPACE AFFAIRS about Falcon 9, linked on its Above Ten Thousand entry. Duration: 26:17. Language: English. Video type: Livestream.
What is being broadcast
Rebroadcast on the Space Affairs channel of SpaceX's broadcast of the launch attempt for the fourth Tranche 1 Transport Layer mission of the U.S. Space Development Agency (SDA). A Falcon 9 was standing by at Space Launch Complex 4E (SLC-4E) at Vandenberg Space Force Base, California, with liftoff scheduled for 1:18 a.m. Pacific time. The commentary is by Annie Tu, a SpaceX operations engineer. Before and after the broadcast, the video includes long stretches with only music.
Key moments
This is the fourth of nine Tranche 1 missions the Falcon 9 will launch for the SDA. It carries 21 data-transport satellites forming the fourth orbital plane of a low-Earth-orbit network for tactical military communications and missile warning and tracking. Once complete, Tranche 1 will total 154 operational vehicles plus four missile-defense demonstration satellites. At the customer's request, footage of the second stage and payload was not going to be shown.
As the countdown proceeds, the host describes the rocket from top to bottom. The payload fairing has two halves that are recovered at sea; both were flying for the second time. Below are the second stage, with a single vacuum-optimized Merlin engine, the carbon-fiber interstage, and the first stage, with nine Merlin 1D engines producing more than 1.7 million pounds of thrust. The booster was making its sixth flight, after NROL-179, SDA T1TL-E, and three Starlink missions, and was due to land at Landing Zone 4 at Vandenberg. The video also explains why propellants are loaded at the end of the countdown — the colder they are, the denser — along with engine chilling, helium tank pressurization, and the retraction of the strongback, which is fully lowered before the countdown's final moments.
Outcome
One minute before liftoff, the Falcon 9 enters the autonomous startup sequence, but the countdown is aborted at T-58 seconds. After a pause, SpaceX confirms the rocket and payload are in good condition, calls off the day's attempt, and announces a new opportunity on October 6 in the same window.