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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 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 launched the all-electric, steering wheel-less, and pedal-less Cybercab last night at a quiet and small event in downtown Austin, Texas.
The launch, which marked the beginning of unsupervised ride-hailing for Tesla’s Robotaxi platform with Cybercab, has already caught the attention of the National Highway Traffic Safety Administration (NHTSA) who has more questions.
NHTSA opened an Audit Query (AQ) into the Cybercab’s Federal Motor Vehicle Safety Standards (FMVSS) certification that Tesla gave the vehicle. Manufacturers self-certify vehicles much of the time to avoid excessive regulatory delays.
Tesla Cybercab interior, note the lack of steering wheel and pedals. (Credit: @niccruzpatane/X< /a>)
However, the agency needs more information; it said in a summary:
“On September 3, 2026, Tesla began commercial deployment with a small number of its Cybercab vehicles in Austin, Texas. Tesla notified the Agency that it certified those Cybercab vehicles as compliant with all applicable Federal Motor Vehicle Safety Standards (FMVSS). Tesla also notified the Agency that it plans to gradually expand commercial deployment of the Cybercab to include additional vehicles and locations.”
It also went on to state that the Cybercab lacks traditional automotive controls, which is a groundbreaking move. The process is entirely new to the NHTSA, which gives the agency some leverage to put Tesla’s launch under a microscope:
“The vehicles lack permanently attached, conventional manual controls, such as a brake pedal, gas pedal, steering wheel, and mirrors. NHTSA is opening this AQ to examine the process and technical data on which Tesla relied when certifying the Cybercab and related issues. Among other things, NHTSA will consider the extent to which Tesla’s certification depended on determinations that certain FMVSS are inapplicable to the Cybercab.”
Tesla has added 45 Cybercab units to its fleet of Robotaxi-enabled cars in Austin, according to public documents the company submitted to the State of Texas over the past week. Enabling this level of self-driving is something Tesla has worked toward for many years, and now that it is finally here, it seems more than reasonable that regulatory agencies will have some questions.
Many outlets might try to frame this as a negative, but it is truly an agency looking to gain more information about groundbreaking tech that Tesla has been developing for years.
In an effort to keep riders, pedestrians, and property safe, any and all data accumulated from these first days, weeks, and months of rides will likely be shared with the NHTSA to enable broader rollout strategies across the United States and more in the future.
Tesla Robotaxi will be a 24/7 service: here’s when
Tesla Full Self-Driving will now overtake manual driving to avoid disaster
