SDA Tranche 0 Launch: Falcon 9’s 13th Flight from Vandenberg

SpaceX launched the Space Development Agency's second Tranche 0 mission on Saturday, September 2, 2023, at 7:25 a.m. Pacific Time from Space Launch Complex 4E at Vandenberg Space Force Base in California. It was SpaceX's 260th launch overall and its 61st of the year, matching the previous year's annual record with four months still to go.

Earlier attempts

Two earlier attempts were stood down. On Thursday, one of the first stage engines was not responding as expected during standard pre-launch checkouts, and the team decided to stand down to take a closer look. On the following day's attempt, a valve on the ground support equipment was behaving out of family. After checkouts and verification that the vehicle and ground equipment were healthy, the team went back into the count with no blockers.

The payloads

The mission carried 11 SDA payloads for the Proliferated Warfighter Space Architecture (PWSA). SpaceX also designed and built two of the payloads, which are part of the PWSA tracking layer, meant to provide global indications, warning, tracking and targeting of advanced missile threats including hypersonic missile systems. SDA aims to deliver capabilities on 2-year timelines. At the customer's request, no views of the second stage were shown and fairing separation was not broadcast, though audio confirmed it.

The vehicle

The payload fairing is about 40 ft long and 17 ft in diameter. Its two halves were flight proven, one flying for the fifth time and the other for the eighth. The first stage, with nine Merlin 1D engines, was flying for the 13th time. Propellant loading brought each stage to nearly full with 1 million pounds of kerosene and liquid oxygen. Stage one finished loading at about T-minus 3 minutes and stage two at about T-minus 2 minutes.

Ascent and landing

The rocket flew straight up until about T+10 seconds before pitching over. It throttled down ahead of max Q, then main engine cut off, stage separation, stage flip, second engine start and the boost back burn followed in quick succession. The first stage then performed an entry burn and a landing burn of around 15 seconds, deploying its landing legs. It landed at Landing Zone 4 at Vandenberg, the 13th launch and landing of this booster and SpaceX's 222nd successful recovery of an orbital class rocket. The webcast ended shortly after the landing.