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SpaceX fires Falcon Heavy’s 27 booster engines ahead of “most difficult launch ever”
For the third time ever, SpaceX has successfully performed a critical static-fire test of an integrated Falcon Heavy, briefly igniting all 27 of its Merlin 1D engines to verify the health and readiness of the rocket.
Per SpaceX’s official confirmation, a “quick-look” inspection of static fire telemetry has indicated that the company’s Falcon Heavy rocket is ready for its second launch in less than three months, a milestone that could also allow both flight-proven side boosters to tie SpaceX’s own record for booster turnaround. Falcon Heavy Flight 3 is now scheduled to launch the US Air Force’s Space Test Program 2 (STP-2) mission no earlier than 11:30 pm ET (03:30 UTC), June 24th. According to SpaceX CEO Elon Musk, the mission will unequivocally be the company’s “most difficult launch ever”.
Coincidentally, on top of being Falcon Heavy’s first scheduled night launch, STP-2 has now also marked the massive rocket’s first nighttime static fire. During this critical test, Falcon Heavy briefly ignites all 27 of its three boosters’ Merlin 1Ds and throttles the engines up to full thrust, much like airliners sometimes set their brakes and throttle up before attempting to take off. The difference between Falcon Heavy and passenger aircraft is nevertheless rather significant, given that Falcon Heavy produces ~15x the thrust of an A380 – the world’s most powerful mass-produced passenger aircraft – at liftoff: 22,820 kN (5.1M lbf) to the massive jet’s meager 1,440 kN (0.3M lbf).
Despite all of that thrust, Falcon Heavy is held down during static fire by eight accurately-named hold-down clamps, themselves a part of a massive transport/erector, which is itself anchored directly to Pad 39A’s concrete foundation. In short, Falcon Heavy (and especially Falcon 9) is not going anywhere until those hold-down clamps are explicitly released. Thanks to SpaceX’s avoidance of the solid rocket boosters used by almost every other modern launch vehicle, Falcon 9 and Heavy rockets can abort at any point prior to clamp release, offering a uniquely broad abort capability.
As such, not only does SpaceX’s dedicated pre-launch static fire fully test the rocket’s health, but the same procedure is essentially repeated in the seconds before clamp release during an actual orbital launch attempt. If at any point Falcon 9’s autonomous onboard computer decides that it doesn’t like any of the thousands of channels of telemetry it’s constantly analyzing, it can command an engine shutdown and total launch abort even if all first stage engines have already ignited and reached full thrust. If routine McGregor, TX acceptance testing – also involving a full static fire – is accounted for, every single Falcon 9 booster technically completes three fully-integrated static fires before its inaugural liftoff. Falcon Heavy is slightly different, as each booster is independent test-fired in Texas but the integrated rocket can only perform static fires at Pad 39A.
After those three critical tests, flight-proven Falcon boosters are subjected to the less stringent few-second static fires SpaceX performs at the launch pad 3-7 days before a given launch. With Falcon Heavy Flight 3, the rocket’s center core, upper stage, and payload fairing are all brand new, fresh from either SpaceX’s Hawthorne factory or McGregor acceptance testing. However, both side cores – Block 5 boosters B1052 and B1053 – are flight-proven, having successfully completed their first launches and landings on April 11th, less than 70 days ago.
Set by regular old Falcon 9 boosters, SpaceX’s current record for booster turnaround time (time between two launches) is 71 days (set in June 2018), while the Block 5 upgrade’s record stands at 74 days (set in October 2018). If Falcon Heavy’s STP-2 launch holds strong on June 24th, B1052 and B1053 will simultaneously tie SpaceX’s Block 5 turnaround record. This would be accomplished despite the added pressure from the US Air Force’s decision to use STP-2 as a sort of dress rehearsal for certifying all flight-proven commercial rockets, an honor (and burden) that likely added extra work, oversight, and scrutiny to the process of refurbishing and relaunching B1052 and B1053.
“[T]he US Air Force has decided that STP-2 presents an excellent opportunity to begin the process of certifying flight-proven SpaceX rockets for military launches. The STP-2-related work is more of a preliminary effort for the USAF to actually figure out how to certify flight-proven commercial rockets, but it will still be the first time a dedicated US military mission has flown on a flight-proven launch vehicle. Down the road, the processes set in place thanks – in part – to STP-2 and Falcon Heavy may also apply to aspirational rockets like Blue Origin’s New Glenn and ULA’s “SMART” proposal for Vulcan reuse.”
— Teslarati.com, 06/16/2019
In a last-second surprise, SpaceX updated Falcon Heavy center core B1057’s planned drone ship landing site from a brief 40 km (25 mi) to more than 1240 km (770 mi) off the coast of Florida. SpaceX set its current record for recovery distance less than three months ago during Falcon Heavy’s commercial launch debut, in which Block 5 center core B1055 landed nearly 970 km (600 mi) offshore on drone ship Of Course I Still Love You (OCISLY). If all goes well, B1057 – the second finished Block 5 center core – will absolutely crush its predecessor’s record, implying that the booster will likely be subjected to SpaceX’s most difficult reentry and recovery yet.
For more on what CEO Elon Musk describes as “[SpaceX’s] most difficult launch ever”, check out these previous articles on an unexpected ultra-fast booster reentry and the extraordinary challenge facing Falcon upper stage.
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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
