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SpaceX first Super Heavy ‘test tank’ is almost ready for prime time
SpaceX has almost completed a ‘test tank’ meant to ensure that Starship’s Super Heavy booster is capable of withstanding the immense thrust of more than two-dozen Raptor engines.
Believed to be known as test tank BN2.1, the prototype’s latest appearance comes on the heels of news from CEO Elon Musk that SpaceX has upgraded Super Heavy with one extra Raptor engine – with plans to add another three down the road. The results of that tank’s imminent test campaign will likely be crucial as the company shifts its focus sending Starship to orbit (or close) as soon as possible.
Prior to a new Super Heavy booster ‘thrust puck’ design first spotted on May 29th, at least two separate booster engine section prototypes completed in the last few months sported an earlier variant more akin to a donut. At that point, Super Heavy’s design had a central cluster of eight gimballing, throttleable Raptors surrounded by a ring of 20 Raptor Boost (“RBoost”) engines – a variant meant to trade the ability to throttle for ~25% more thrust.
While Super Heavy booster BN1’s almost immediate scrapping – prior to a single test – guaranteed that major design changes were on the way, exactly what those changes would be was anyone’s guess. The appearance of a new booster ‘thrust puck’ design and Musk’s subsequent announcement that Super Heavy will “initially” have 29 – not 28 – Raptors likely mean that that engine section redesign was a major contributor to BN1’s instant obsolescence. The only other major change SpaceX clearly made with booster BN2 was switching the positions of its liquid methane and liquid oxygen tanks, ensuring that Super Heavy’s heavier oxidizer is closer to the rocket’s base.
Musk also stated that SpaceX will eventually upgrade Super Heavy to 32 engines, giving future boosters a central cluster of 12 engines that the SpaceX CEO says will significantly improve the efficiency of boostback burns.
With 29 identical Raptors, the simplest possible Super Heavy booster would produce up to 5800 tons (12.8M lbf) of thrust at liftoff. If SpaceX has already completed Raptor Boost’s design and qualification and kicked off mass production of a 250-mTf engine, that liftoff thrust climbs to 6800 tons (~15M lbf). If SpaceX achieves performance goals (~210 mTf stock; ~300 mTf RBoost) mentioned by Musk last year, a 32-engine Super Heavy could achieve peak liftoff thrust greater than 8500 metric tons (~18.7M lbf).
Even in its weakest configuration, Super Heavy will still be more than 60% more powerful than Saturn V and 25% more powerful than N1 – the largest rockets to have ever successfully or unsuccessfully flown. That immense thrust demands a structure capable of surviving those extreme forces while simultaneously feeding dozens of Raptors up to ~28 metric tons (~61,000 lb) of propellant every second and withstanding several thousand tons of liquid oxygen – all without leaking, cracking, or flexing too much.
While BN2.1 wont have any of the plumbing associated with dozens of Raptors, nine hydraulic rams will let SpaceX subject its Super Heavy thrust structure to the simulated thrust of some number of engines. Given the presence of nine rams and nine clustered engines, it’s unclear if BN2.1 will only test that main thrust structure or if those rams will somehow be spread out to simulate the thrust of a full 29 engines – 20 of which will instead transfer most or all of their thrust into Super Heavy’s skirt.
Regardless, if successful, BN2.1’s test campaign should leave SpaceX on track to attempt Starship’s inaugural spaceflight as early as Q3 2021. If issues arise, that target could easily slip to Q4 or into 2022, but SpaceX’s test tank campaigns have historically been very successful.
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
