Over the weekend, the Lab Padre feeds noted that intermittent road closures had been set for today but that the beach would remain open. Your Secret Decoder Ring will translate that to mean they're likely to be moving something big on the road between the launch complex and the shipyard. I checked in on them around 10AM their time and found Booster 4 completing its journey from the high bay to the launch area. Photo by Starship Gazer on Twitter with H/T to Teslarati.
The Tweet was time tagged 9:33 AM, so 10:33 my time.
Deemed Super Heavy Booster 4 or B4, the 69m (~225 ft) tall rocket first rolled to the launch pad around August 3rd after SpaceX technicians fitted it with 29 Raptor engines in a single night. Followed by orbital-class Starship prototype S20 a few days later, the two stages of a Starship were stacked to their full height on August 6th, briefly creating the largest rocket ever assembled. Ship 20 was then quickly returned to the build site, where SpaceX workers completed an additional ~10 days of finishing touches – mainly focused on avionics wiring and secondary plumbing.
A week later, Booster 4 followed Ship 20 back to Starbase’s ‘high bay,’ where teams ultimately removed all 29 of its Raptor engines and spent the next four or so weeks performing similar final integration work. Now, after installing what looks like hundreds of feet of wiring, dozens of additional gas and fluid lines, compressed gas tanks, hydraulic ‘sleds’ SpaceX’s first flightworthy Super Heavy has once again returned to the launch site
It's pointless to predict when they'll do things, but I strongly suspect that we're going to see some of the tests they need to do before trying to orbit this beast rather than a repeat of last month's ballet of sending both to the test area, photo op stacking, then sending both back to the shipyard. They'll pressurize it, ensure it works well with cryogenic fluids, and do static fires. They'll test not just B4, but also Starship S20 which is currently on a test stand not too far away.
At the moment, B4 is still not on the Orbital Launch Pad but the big crane, Kong, is connected to a harness at the top of B4 and could hoist it any moment. I think that the first time, August 4th, it was placed on the OLP the next day.
RGV Aerial Photography, who does regular flyovers of the SpaceX facilities for their YouTube Channel Tweeted this photo of the OLP back on August 20th. They point out structures they think are part of the water deluge system for the OLP but which Teslarati suggests are actually umbilical connectors for the Raptor Boost engines. Regardless, they're going to need a water deluge system when they light 29 Raptors on the bottom of B4. That system will need to be tested as well.
Final words to Eric Ralph of Teslarati:
That testing will be part of a much more involved test campaign. Namely, if SpaceX intends to test Super Heavy Booster 4 at the orbital launch site, any booster testing will simultaneously require the shakedown of the orbital pad’s extensive, custom-built tank farm and a wide range of other ground infrastructure that simply didn’t exist at the start of 2021. Booster 4 qualification is no less daunting, as no Super Heavy has ever been fully tested. Now in the midst of being scrapped in place at SpaceX’s suborbital test facilities, Super Heavy Booster 3 did complete a partial cryogenic proof test and a static fire with three Raptor engines, but SpaceX has never fully filled a Super Heavy with >3000 tons (~6.6M lb) of propellant and never static fired more than three Raptor engines simultaneously.