Both Ship 20 and Booster 4 are being prepped for testing ahead of the milestone Orbital Launch attempt, following the famous first view of a fully integrated Starship stack during fit inspections on the Orbital Launch Site (OLS) mount. Booster 4 is undertaking final closeout work within the High Bay, while Ship 20 has returned to the launch site and taken up suborbital Pad B ahead of proof testing goals.
The pre-launch campaign is still going on, but SpaceX is already planning for the future, with changes to future Starship designs and plans to ramp up production with a second, much larger High Bay. Booster 4 (B4), the first Super Heavy slated to launch, is now living within the High Bay for “some little plumbing and wiring” processing, according to Elon Musk. After being provisionally merged with Ship 20 at the OLS, the booster returned to the production site on August 11.
After the first Super Heavy, Booster 3, was sent to the Orbital Launch Site, Booster 4 became a milestone. The three-engine Static Fire test was done by Booster 3 (B3), marking the first time a Super Heavy had fired up a pair of Raptors. While it was possible that B3 would go on to conduct a nine-engine test, Musk hinted that the plans had been changed due to the readiness of Booster 4’s campaign. Booster 3 has since began the process of being discarded, with work being undertaken at Suborbital Pad A.