SpaceX accelerates Booster 19 assembly to stay on track for 2026 Starship launch

SpaceX is making significant strides in the assembly of its Super Heavy Booster 19 at the Starbase facility, with plans to have the stacking completed by the end of December. This effort aims to mitigate any setbacks to the upcoming orbital flight test program, especially following the issues encountered with Booster 18 last month. In parallel, Ship 39, which is also being prepared, will undergo a series of tests at Massey’s, setting the stage for a potential launch window in February to March 2026.

The urgency surrounding Booster 19’s development is to ensure that the Starship Flight 12 – featuring upgraded Block 3 vehicles – remains on schedule for its inaugural flight, projected for early 2026. Recent updates indicate that critical assembly milestones are being achieved; welding of the liquid oxygen (LOX) tank to the engine section has been completed, including the installation of pre-mounted landing tanks and transfer tubes. Additionally, methane tank barrels and the forward dome, features an hot staging ring, have been successfully added.

As of December 20, all barrel sections for Booster 19 have been assembled and stacked within an impressive timeframe of just 25 days since November 25, significantly quicker than the 42 days required for the previous Booster 17. The final stages of stacking will include assembling the upper section and securing both halves with two welds, a process facilitated by internal cranes and a ring stand that signals the completion of the structure. With only nine days left in December, SpaceX seems well on track to achieve its goal.

Recent activity on December 23 revealed that preparations are advancing swiftly. A vital tool for the assembly, the LOX landing tank installation stand, has been relocated into Mega Bay 1, where it will assist in positioning the CH4 tank atop the LOX tank, concluding the stacking process for Booster 19.

Post-stacking, the booster will undergo outfitting before undergoing cryogenic proof tests at Massey’s Outpost, although the schedule for these tests remains fluid. Concurrently, Ship 39 – the first of the Version 3 upper stages designed to work alongside Booster 19 for Flight 12 – continues its preparation in Mega Bay 2. Fully stacked since late November, Ship 39 recently exchanged its composite overwrapped pressure vessels (COPVs) as part of ongoing enhancements following a previous failure that resulted in the destruction of Ship 36 in June.

Despite a lack of official confirmation, the timeline of these activities has raised eyebrows, especially considering the recent incident involving a LOX tank rupture during a gas system test on Booster 18. The timing of the COPV exchange suggests that more extensive internal work may have been necessary than originally planned. Ship 39 is now preparing for cryogenic proof testing on a thrust simulator stand at Massey’s, which subjects the vehicle to simulated loads from Raptor engines. After these initial tests, it will return to Mega Bay for the installation of its engines before the crucial static fire tests begin.

Enhancements are also underway in the static fire area at Massey’s, including the addition of a new truss structure that may provide better access during engine evaluations. Meanwhile, SpaceX is conducting validations on the redesigned Version 3 engine section through test tanks, with S39.1, the only current Version 3 ship testing article, having completed its final round of testing earlier this month.

The parallel efforts in both ship and booster development underscore SpaceX’s ambitious strategy to iterate quickly on the Starship’s Block 3 design, which promises improved performance and reusability for future missions. Although the exact launch date for Flight 12 remains tentative, sources suggest that March could be the most likely timeframe for this highly anticipated mission, which will showcase the new vehicle, its Raptor 3 engines, and an upgraded launch infrastructure being implemented at Pad 2, with similar upgrades planned for other pads, including those on the East Coast.