After “unstacking” the Starship S20, SpaceX has officially removed the Super Heavy Booster B4 from Starbase’s only orbital launch mount – and likely for the last time.
Standing about 69 meters (~225 feet) tall and likely weighing at least 200 tons (~440,000 lbs), Booster 4 has been at SpaceX’s Starbase (OLS) orbital launch site for over six months – only slightly less time than Starship S20, which it was eventually to launch into space. Many of those months were spent sitting atop the 22-meter-tall (~70-foot) orbital launch pad, which was slowly but surely outfitted, modified, and tweaked into something capable of withstanding basic Super Heavy testing.
In total, Booster 4 performed more than half a dozen cryogenic proof tests, but never seemed to move on to more complex and valuable repeats – replacing neutral liquid nitrogen with flammable liquid methane and propellant. oxygen to simulate preparations for a real launch. More importantly, despite installing 29 proven Raptor engines for months, Super Heavy B4 never even attempted to fire statically. a of these engines, where a successful static fire of 29 engines is probably the most important test a thruster will have to pass to be cleared to fly.
As a result, the writing has been on the wall for Booster 4 for quite a while. Instead of investing in testing the booster, which has a somewhat outdated two-pronged design, it looks like SpaceX will instead transfer crucial qualification testing to Super Heavy Booster 7. As previously reported, in addition to general improvements made to process, fit and finish throughout, Booster 7 is noticeably different from Booster 4.
“The Super Heavy B7 and Starship S24 feature a wide range of design changes, including significantly modified header tanks, an entirely new nose design, new arrangements for secondary systems (pressurization, avionics, intercoolers heat, etc.), and more. Most importantly, their thrust structures – giant machined steel “pucks” – were modified to support the new Raptor V2 engines instead of the Raptor V1 and V1.5 engines that were installed and tested on all prototypes. Starship and Super Heavy to date. .”
Teslarati.com – March 22, 2022
One could easily argue that SpaceX should have made better use of the months and months when Super Heavy B4 was inactive and largely intact at Starbase launch facilities – instead using that time to perform basic static fire tests which would have even could be made to one of the two suborbital launch mounts if the orbital mount was not ready. Still, regardless of this seemingly squandered opportunity, it makes sense that SpaceX now wants to cut its losses and focus on prototypes with significant upgrades and improvements.
Then SpaceX will continue to stack and outfit Starship S24. Already fully stacked, Super Heavy B7 could be taxied to the orbital launch site at almost any time over the next week or two to begin simpler pneumatic and cryogenic proof testing, followed by installation of the Raptor V2 engine and the start of static fire tests.