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SpaceX rolls Super Heavy booster to orbital launch mount
For the third time in four months, SpaceX has rolled the first potentially flightworthy Super Heavy booster towards Starbase’s orbital launch mount.
Combined with a large crane – fitted with a jig solely used to lift boosters – moving to a spot just beside the booster, it’s clear that SpaceX is preparing to reinstall Super Heavy Booster 4 (B4) on the orbital launch mount. In the context of its unusual history, though, what happens next to the first more or less finished prototype of the largest rocket booster ever built is less clear.
After a shockingly quick assembly over the course of six summer weeks, Super Heavy Booster 4 rolled out of Starbase’s ‘high bay’ facility and headed to the nearby orbital launch complex, where it was installed on a custom ‘mount’ designed to support booster testing and orbital launches. It’s now clear that during that early August photo opportunity and fit test, Booster 4 was nowhere close to finished. Nor, apparently, was it anywhere close to complete one month later when it returned to the orbital pad for the second time after another few weeks of work back at the high bay.
Three months (almost 14 weeks or 100 days) after the Super Heavy prototype’s second trip to the pad, SpaceX has yet to attempt to put the booster through a single proof test. There also appears to be a significant amount of work left to finish installing external ‘aerocovers’ and a heat shield meant to enclose all 29 of its Raptor engines. In the three-year history of Starbase, there isn’t a single prototype of the roughly two-dozen SpaceX has built, tested, and even flown that’s spent even half as long as Super Heavy B4 between apparent structural completion and its first test. Perhaps the fact that Booster 4 is a first-of-its-kind pathfinder explains SpaceX’s uncharacteristic sluggishness or reluctance to actually test the rocket.
In every other instance, SpaceX’s approach to Starship development has been to move incredibly quickly, build a large number of prototypes, and rapidly test those prototypes – often resulting in catastrophic failures. Data is gathered from those failures (SN1, SN3, SN4, SN8, SN9, SN10, SN11, and half a dozen smaller test tanks serve as examples), changes are made, and then the new and improved prototypes that follow repeat the process until SpaceX arrives at a successful design.
Super Heavy B4’s circuitous path has been almost nothing like those of its predecessors. That could also be partly explained by the unavailability of a stand or facilities capable of truly proof testing a Super Heavy, which necessitates a supply of around 3200 tons (7M lb) of liquid nitrogen (LN2; for a cryogenic proof test with full tanks), another 3200 tons of a combination of liquid methane (LCH4) and oxygen (LOx), and the ability to ignite – and survive – as many as 29 to 33 Raptor engines. The suborbital stands SpaceX has used to proof Starships and even Super Heavy Booster 3 don’t even have half the storage capacity required to fully test a booster and the mounts and their surroundings would likely be catastrophically damaged or destroyed by the thrust and blast created by dozens of Raptors.
Still, SpaceX could have theoretically put Booster 4 through a partial cryoproof and maybe fired up as many as nine Raptors at once – not a replacement for full proof testing but still plenty to ensure Super Heavy’s structural integrity and gather invaluable data on clustered Raptor performance. Instead, of course, Super Heavy B4 has sat at Starbase’s former landing zone for more than three months while teams removed engines, reinstalled engines, half-installed a full Raptor heat shield; and installed two of six or seven ‘aerocovers’ needed to protect heat exchangers, racks of pressure vessels, and hydraulic systems installed on the booster’s aft.
This is all to say that from the outside looking in, Booster 4’s path towards testing and flight has been almost entirely different from that of any other Starship prototype. While still quick in comparison with other launch vehicle development programs, relative to other Starship and Super Heavy prototypes, the rate of B4 progress has been far slower – strongly implying that something is seriously wrong with the booster, that SpaceX no longer feels that partial testing is worth the effort, that finishing Booster 4 just hasn’t been a priority for several months, or some combination of the above.
What that ultimately means is that it’s almost impossible to predict what Super Heavy B4’s future holds beyond the clear evidence that SpaceX will soon reinstall to reinstall it on an orbital launch mount that’s much closer to completion than it was the last time B4 was installed. At this point, it’s just as likely that the booster’s third launch mount installation will just be another mechanical fit test, though the hope is that it will kick off full-scale pneumatic and cryogenic proof testing. It could even culminate in the static fire of some or all of its 29 Raptor engines, which have been installed for several months.
Tesla has reached a notable benchmark in its autonomous driving program after its Robotaxi fleet surpassed one million miles of unsupervised operation. The company made the announcement during its Cybercab event in Austin on September 3.
Tesla Vice President of AI Ashok Elluswamy told attendees he was happy to report the fleet had achieved one million miles of unsupervised Robotaxi operation as a testament to safety.
The new total marked a sharp increase from the 380,000 unsupervised miles Tesla disclosed during its second-quarter 2026 earnings update in late July.
In roughly six weeks, the company added about 620,000 miles. That acceleration followed Tesla’s decision to remove in-vehicle safety monitors from most of its operations outside the San Francisco Bay Area.
Credit: Tesla
Tesla first launched Robotaxi service in Austin in June 2025 with safety drivers present. It later began fully unsupervised rides and expanded into Dallas, Houston, Miami, Orlando, and Tampa. The San Francisco Bay Area remains the exception, where a safety monitor still rides in the vehicle under California permitting rules.
The company has not released a city-by-city breakdown of the one million unsupervised miles.
The milestone arrived as Tesla began offering public Cybercab rides in Austin. The purpose-built vehicle has no steering wheel or pedals and is designed only for autonomous ride-hailing. Production versions joined the existing fleet of modified Tesla vehicles already operating in the service.
Tesla’s unsupervised mileage is growing at a double-digit weekly rate according to earlier company comments, yet its fleet size remains modest compared with established competitors. Waymo has accumulated more than 200 million fully autonomous rider-only miles. Tesla has described its own unsupervised operations as having recorded zero notable incidents in the period leading up to the July update.
The one-million-mile figure reflects Tesla’s shift from supervised testing to broader driverless service in multiple states. It also highlights the company’s strategy of using both existing Model Y vehicles and the new Cybercab to scale its network.
Credit: Tesla
Whether the rapid recent growth continues will depend on further city expansions, regulatory approvals, and the performance of the purpose-built Cybercab in everyday paid rides. Tesla has not specified how many of the latest miles involved the new vehicle versus the rest of the fleet.
The announcement underscores Tesla’s progress toward a larger robotaxi network while illustrating the remaining gap in total autonomous experience relative to longer-operating rivals.
Tesla AI lead Ashok Elluswamy said this week that 24-hour Robotaxi service is close. Replying on X to a rider who wanted Cybercab trips all night, he wrote that the capability would arrive “next month or so” once “the next tech to merge on the v15 plan” is ready.
The comment landed on September 4, one day after Tesla opened public Cybercab rides in Austin. It is the clearest near-term timeline yet for overnight unsupervised operation. Tesla’s paid Robotaxi network currently runs from 6 a.m. to 10 p.m. seven days a week across Austin, Dallas, Houston, Miami, Orlando, and Tampa.
next month or so. the next tech to merge on the v15 plan will enable it.
— Ashok Elluswamy (@aelluswamy) September 4, 2026
That 16-hour window is shorter than the 6 a.m. to 2 a.m. schedule the company used for much of the prior year.
Elluswamy did not name the specific feature or say whether the change would apply first to purpose-built Cybercabs, the existing Model Y fleet, or both. He also offered no city-by-city rollout list. The link to Full Self-Driving v15 is nevertheless significant.
Tesla has described v15 as a step-change architecture with seven parallel improvement tracks and roughly ten times more parameters than earlier builds. Early versions of that software already operate on the Robotaxi fleet and contain about 40 percent of the planned gains.
By July 2026, the unsupervised fleet had logged more than 380,000 miles across six cities in two states with what the company called an impeccable safety record and no notable incidents caused by the vehicles themselves. Tesla has repeatedly argued that camera-based end-to-end neural networks, rather than extra sensors, are the core of the solution.
Overnight service would test that claim in lower-light conditions and would also raise vehicle utilization, a key variable for Robotaxi unit economics. The company has already begun using public Superchargers at night and is building dedicated Robotaxi charging sites.
Riders have asked why software must change if the cars already drive in the dark. The practical answer appears to be reliability and scale: Tesla has held back mass expansion until more of the v15 stack is merged, citing the need for higher confidence before putting thousands of unoccupied vehicles on streets around the clock.
If the next module arrives on the timetable Elluswamy sketched, 24-hour service could begin in October 2026 in at least some markets.
That would mark a shift from a daytime-bounded pilot to a service that can run whenever demand exists, including the late-night hours that have so far remained out of reach.
Tesla is beginning to roll out Full Self-Driving Supervised v14.3.9 with a new active safety layer that can take control even when the driver is operating the car manually.
Tesla AI said the software can activate FSD on the driver’s behalf when an imminent collision is detected and Automatic Emergency Braking may not be enough. It may also engage if the system detects heavy distraction or an accidental FSD disengagement.
FSD Supervised v14.3.9 starting to roll out shortly
This release includes a new active safety feature set: FSD Supervised can now activate on your behalf when an imminent collision is detected and Automatic Emergency Braking (AEB) may not be enough.
It may also engage if we…
— Tesla AI (@Tesla_AI) September 4, 2026
The capability is essentially Automatic Collision Evasion. However, unlike conventional AEB, which mainly applies the brakes in a straight line, this feature can use steering, braking, and acceleration together if the car calculates that stopping alone will not prevent impact and a safer path exists. The system may change lanes or move toward a shoulder when conditions allow, then continue driving after the immediate threat is handled rather than simply coming to a stop.
The intervention is meant as a last-resort safety net, not a replacement for attentive driving.
Tesla Full Self-Driving v14.3.7 early review: FSD saved me from an accident
Tesla’s own description still frames FSD as supervised assistance. Secondary reports on internal release notes say the feature can fire while the car is being driven manually if cabin-camera monitoring suggests the driver is not sufficiently attentive, such as reaching toward the back seat, or if FSD appears to have been turned off unintentionally.
After the emergency maneuver, the car is expected to alert the driver and request a return to manual control.
The safety case is straightforward. Many collisions happen in the last second because a driver is looking away, fumbles a control, or faces an obstacle that braking cannot fully solve. A system that can both recognize that AEB is insufficient and execute a coordinated evasive path can reduce those remaining high-severity events.
Re-engaging after accidental disengagement also addresses a practical failure mode: a small steering nudge that drops FSD at the worst moment. The advantage is a background safety net that uses the same vision stack already running in v14, instead of leaving the car solely to emergency braking once the driver is no longer in command.
The feature still depends on FSD being enabled and, according to reports, an active FSD purchase or subscription. It does not make the vehicle unsupervised. Drivers remain responsible, and Tesla has not published how often the system is expected to intervene or how it will handle false positives.
If the rollout is conservative and the false-alarm rate stays low, the update is a meaningful step: FSD is no longer only a feature the driver turns on. In the rare moments when disaster is already forming, it can step in.
Tesla crosses major Unsupervised Self-Driving milestone
Tesla Robotaxi will be a 24/7 service: here’s when
