Booster 4

History

Booster 4 is a Super Heavy booster that is currently under construction in Boca Chica, Texas.

It was reported by NASASpaceFlight.com that Ship 20 (previously known as SN20) with Booster 4 (originally planned to be BN3, which instead was incorporated into Booster 3) would attempt an orbital test launch by 1 July 2021. The launch scheduled was later pushed back into July/August.

This was later confirmed by Elon Musk who tweeted that Booster 4 would be the first one to fly, while Booster 3 would be used in ground tests. There would be significant design changes between Booster 3 and 4 as there had been difficulties in the construction of Booster 3.

A section of Booster 4 was spotted in the High Bay on 3 July 2021. By 21 July it had been stacked to twelve rings tall, with the Methane Transfer Tube (aka Downcomer pipe) being installed in the early hours of 27 July. The launch appeared to take on new urgency with Elon Musk ordering several hundred of SpaceX’s employees at Hawthorne to relocate to Boca Chica to speed up the development of Ship 20 and Booster 4, along with the Orbital Launch Platform to have the Starship system on the pad by 5 August.