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SpaceX preparing for third Starship ‘full stack’
SpaceX appears to be preparing Starship 20 and Super Heavy Booster 4 for their third ‘full stack’ demonstration after two seemingly successful tests in August 2021 and February 2022.
The first, completed in early August 2021, was mostly for show and saw SpaceX stack the unfinished prototypes with a giant crane – fighting the coastal winds throughout. After just a few hours stacked, Ship 20 was removed and returned to Starbase, where workers spent several more weeks (mostly) finishing the prototype. Booster 4 followed suit several weeks later and ultimately took another three months of work to reach some level of test readiness.
After Ship 20 and Booster 4 completed a series of tests in the last few months of 2021 and early 2022, the two were re-stacked in mid-February – once again for show. This time, the stacked Starship served as a backdrop for SpaceX CEO Elon Musk’s first official Starship presentation in more than two years. However, despite the fact that neither prototype was actually tested during the second stack, SpaceX did use the opportunity to partially debut Starbase’s ‘orbital launch integration tower’ and used that towers trio of giant arms to lift, stack, and stabilize Starship S20 on top of Super Heavy B4.
Ship 20 was ‘destacked’ with the tower’s arms just a few days after Musk’s event – an undeniably rapid and impressive achievement for the first real use of the ‘chopstick’ arms but still far from demonstrating that Ship 20, Booster 4, or the orbital launch site (OLS) are ready for orbital test flights. Since then, however, Starbase’s launch facilities have admittedly been almost as busy as they’ve ever been with Starship and Super Heavy cryoproof tests.
Ship 20 completed its first basic OLS cryogenic proof test or ‘cryoproof’ just two days after it was destacked. Additional Starship S20 cryoproofs followed on February 17th (the day after), February 22nd, and March 3rd. Super Heavy B4 completed its own cryoproofs on February 18th and March 1st, the latter of which may have actually been the fullest a Starship booster has ever been filled. All told, SpaceX completed no less than six major B4/S20 cryoproof tests in 15 days.
Crucially, all six cryoproofs were performed with Starbase’s nascent orbital tank farm, thoroughly testing its storage and distribution capabilities. Additionally, because SpaceX began liquid methane deliveries on February 13th, some of those tests – particularly with Ship 20 – may have even been proper wet dress rehearsals, meaning that SpaceX may have filled the rocket(s) with liquid methane (LCH4) and liquid oxygen (LOx) propellant to replicate preparations for a real launch.
At a minimum, Super Heavy Booster 4’s oxidizer tank was fully filled with liquid oxygen – and possibly pressurized with hot gaseous oxygen – during its March 1st cryoproof, while its fuel tank was filled about two-thirds of the way either with liquid nitrogen (LN2) or methane. Prior to its February and March tests, Booster 4 had already completed three cryoproofs – some also using LOx – in December 2021. Ship 20 had completed a cryoproof and four static fire tests.
All told, short of finally performing a full Super Heavy wet dress rehearsal and static fire at the orbital launch site, it’s not all that clear what more SpaceX can derive from additional individual cryoproof testing of Ship 20 or Booster 4. Several things do still need to be demonstrated, however. First, the OLS launch tower has yet to use its arms to remotely install a Super Heavy on the orbital launch mount. More importantly, SpaceX has yet to use the launch tower and its swinging ship umbilical arm to cryoproof or fuel a Starship while stacked on top of a Super Heavy. Finally, SpaceX has also yet to simultaneously perform a cryoproof or wet dress rehearsal test of a stacked Starship and Super Heavy, which will be necessary for orbital test flights.
One or several of those to-be-completed tests may be why SpaceX appears to have begun preparing to install Ship 20 on top of Booster 4 for the third time. On March 14th, Starship S20 was moved towards the launch tower and on March 15th, the ship was slotted between its ‘chopstick’ arms. Based on stack #2, the ship could be lifted at any point – day or night – and installed on top of Super Heavy in a matter of hours.
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
