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Ex-SpaceX engineer leads Stratolaunch to major rocket engine test milestone

Stratolaunch has successfully completed the first full-scale test of its 200,000-lbf thrust PGA rocket engine. (Stratolaunch)

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Led by rocket propulsion expert Jeff Thornburg, Stratolaunch – famous for owning the largest fixed-wing aircraft ever built – has completed the first hot-fire test of a full-scale rocket engine component known as the preburner, a major milestone in the development of any launch vehicle or propulsion system.

Despite the significant size and power of the component, destined to support an engine that will generate 200,000 pounds (~900 kN) of thrust, Thornburg and his team of engineers and technicians have managed to go from designing the preburner to successfully hot-firing a full-scale test article, an extraordinary achievement by any measure.

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Aside from SpaceX, Blue Origin, and Aerojet-Rocketdyne, Stratolaunch is the only private entity developing – let alone testing full-scale parts for – a liquid-fueled rocket engine as large as PGA. Shorthand for the Stratolaunch’s late founder and bankroller Paul G. Allen, PGA is a fuel-rich staged combustion cycle engine that uses liquid hydrogen and oxygen (hydrolox) fuel and oxidizer, typically resulting in high efficiency. In terms of scale and thrust, PGA is very closely comparable to SpaceX’s Merlin 1D engine, which uses kerosene instead of hydrogen but produces roughly 190,000 lbf (850 kN) of thrust and stands 4 feet (1.2m) wide and ~10 feet (~3m) tall.

Another major difference between PGA and Merlin 1D is the fact Merlin 1D’s nozzle is largely optimized for sea level while PGA is being built for a rocket that will be “launched” from a massive plane flying around 35,000 feet (~10.5 km), ultimately resulting in a nozzle that is much wider and longer, featuring nearly the same proportions as fully vacuum-optimized engines like SpaceX’s MVac. By widening the nozzle relative to the rest of the engine, rocket engines are able to operate far more efficiently at higher altitudes, where Earth’s atmosphere thins and exerts less pressure on the escaping exhaust gases. This is visualized well by the visible expansion of rocket exhausts during launches, morphing from a straight cylinder to a massive teardrop-shaped plume. At lower altitudes (and thus higher atmospheric pressures), wider nozzles can produce extreme turbulence and will ultimately shake themselves to destruction, preventing their usage on ground-launched rocket boosters.

Judging from official renders of the engine, PGA’s in-atmosphere variant appears to utilize a form of regenerative nozzle cooling very similar to that used on M1D, where liquid propellant flows through thin capillaries sandwiched between two or more layers of metal to cool the nozzle much like cold water chills the skin of an uninsulated water bottle.

Testing rocket engine preburners

In the case of staged combustion cycle hydrolox rocket engines, a small portion of liquid oxygen and all of the liquid hydrogen (hence “fuel-rich”) are mixed and combusted to generate hot gas that then spools up the engine’s primary turbopump(s), ultimately drawing fuel and oxidizer into the combustion quickly enough to ignite the engine and generate sustained thrust. The components that get those main turbopumps started are known collectively as the preburner, which is what Stratolaunch successfully tested – at full-scale – for the first time ever last week. For any liquid rocket engine that cannot solely rely on propellant tank pressure to deliver fuel to the combustion chamber, full-scale tests of preburners or gas-generators effectively mark the moment that engines truly become real.

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“This is the first step in proving the performance and highly efficient design of the PGA engine. The hot-fire test is an incredible milestone for both the propulsion team and Stratolaunch.” – Jeff Thornburg, VP of Propulsion, Stratolaunch

Stratolaunch’s propulsion team will continue to test the preburner for longer durations and at higher power levels over the next several months, likely optimizing operations and tweaking or upgrading the preburner’s hardware as real tests produce valuable lessons-learned. Built entirely with additive manufacturing (3D printing), the team should be able to rapidly iterate on the physical design of the engine, a rarity in a field where traditional fabrication methods can take weeks or months to produce complex turbomachinery components with mercilessly strict tolerances.

According to Thornburg, the ultimate goal is to continue that additive-manufacturing-only strategy throughout the development of this rocket engine, theoretically enabling unprecedented design flexibility while also slashing production time throughout. PGA will ultimately power the creatively-named Medium Launch Vehicle (MLV), a small-ish air-launched rocket designed to place a respectable 3400 kg into low Earth orbit (LEO) as early as 2022, as well as a Heavy version of MLV and, potentially, a reusable spaceplane somewhere down the line.

 


For prompt updates, on-the-ground perspectives, and unique glimpses of SpaceX’s rocket recovery fleet check out our brand new LaunchPad and LandingZone newsletters!

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Eric Ralph is Teslarati's senior spaceflight reporter and has been covering the industry in some capacity for almost half a decade, largely spurred in 2016 by a trip to Mexico to watch Elon Musk reveal SpaceX's plans for Mars in person. Aside from spreading interest and excitement about spaceflight far and wide, his primary goal is to cover humanity's ongoing efforts to expand beyond Earth to the Moon, Mars, and elsewhere.

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Tesla Full Self-Driving and App Connectivity save life in medical emergency

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Credit: Tesla

In a remarkable demonstration of how advanced vehicle technology can intersect with family care and rapid response, a Tesla Model Y equipped with Full Self-Driving (FSD) Supervised helped save a driver’s life during a severe heart attack. The incident, which occurred on November 15, 2025, highlights the life-saving potential of Tesla’s connected ecosystem.

John Brandt, 55, was driving his new 2026 Model Y Launch Edition on Interstate 20 from Atlanta toward Birmingham early that morning. He had recently received the FSD v14.1.3 update. Around 3:50 a.m., he began experiencing severe chest pain. Barely conscious and unable to safely control the vehicle, John managed to call his son, Jack Brandt.

FSD Supervised remained engaged, keeping the car steadily on course while John reached out for help.

As an authorized driver on his father’s Tesla account, Jack quickly sprang into action from his own phone. He located Tanner Medical Center in Carrollton, Georgia—a facility equipped for cardiac emergencies—via Google Maps and shared the destination directly through the Tesla app.

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The Model Y responded immediately, rerouting: it took the next exit, turned around on I-20, navigated local roads, and pulled directly up to the emergency room entrance. Jack also alerted hospital staff that a heart attack patient was en route in a Tesla.

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Doctors diagnosed John with a massive STEMI heart attack, requiring immediate intervention on three blocked arteries. They later confirmed that without the swift reroute, John likely would not have survived—whether he had pulled over to wait for an ambulance or attempted to continue driving. He received life-saving treatment and is now recovering fully.

Tesla shared the story on X, including an interview video featuring John and Jack reflecting on the event. John described the terrifying onset of symptoms, while Jack detailed the ease of remote intervention thanks to the app’s features. Only authorized users with vehicle access can change navigation destinations, adding a layer of security and family coordination.

This case underscores Tesla’s emphasis on connectivity and supervised autonomy. Features like remote navigation allow loved ones to assist in real-time emergencies, while FSD handles complex driving tasks reliably. Tesla notes that FSD Supervised requires active driver supervision and is not fully autonomous; this was a specific incident, not a general emergency protocol.

The story has resonated widely, with many praising Tesla’s technology for bridging gaps in critical moments. Jack previously shared details on social media in February 2026, and Tesla’s recent post has amplified its reach. As vehicles become smarter and more connected, such integrations could redefine personal safety on the road—turning cars into proactive partners in health crises.

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For Tesla owners, the incident serves as a powerful reminder to add trusted family members as authorized drivers and explore FSD capabilities. While no technology replaces professional medical care, this blend of AI-assisted driving and seamless app control proved invaluable. John’s survival stands as a testament to innovation that prioritizes human life.

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Elon Musk predicts Grok will start to challenge Hollywood by the end of 2026

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Gage Skidmore, CC BY-SA 4.0 , via Wikimedia Commons

In a bold declaration on X, xAI CEO Elon Musk announced that its model will be capable of creating full movies by the end of the year. Quoting an xAI post showcasing a stunning AI-generated trailer for Homer’s The Odyssey, Musk simply stated: “Full movies by the end of the year.”

The quoted video, created entirely with the newly released Grok Imagine Video 1.5, demonstrates the rapid strides in AI video generation. Crafted by creator David Thompson, the 2-minute-plus trailer reimagines the ancient epic in the style of a 1970s classical Hollywood blockbuster. It features 36 meticulously consistent shots that form a cohesive narrative world.

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Its realistic nature is truly mind-blowing, and it’s pretty amazing to think that it cool to think it could create an entire movie soon.

The trailer reimagines The Odyssey as a whole, and opens with a concept board outlining the vision: a retelling of the story using 35mm film aesthetics, classical framing, and other elements.

There are a handful of things that truly outline Grok’s capabilities:

  • Scale and Physics: A bloodied Spartan helmet rests on a sandy battlefield amid smoke, marching armies, and flocks of birds. Horses gallop, chariots charge, and warriors clash with believable weight and motion.
  • Emotional Depth and Dialogue: Close-ups capture intense expressions, as characters deliver lines like a warrior’s grief-stricken speech on a rocking ship.
  • Cinematic Workflow: It’s hard to believe AI created this trailer, as editing and suspense are clearly detailed in this trailer

Now, why is this a big deal? AI has been a real threat to the way movies have been made over the past several decades. It’s no secret that the various AI platforms out there are becoming more capable, but Musk has said that he believes things would be “watchable” by the end of this year, and by the end of 2027, Grok would be able to create “really good” movies.

There are several issues that remain, most notably the ability to remain cohesive throughout the length of a film, energy requirements, copyright questions for training data, and artistic intent. Hollywood has created some of the greatest cinematic masterpieces over the past 100 years, but 2026 could be the year AI not only assists but also independently authors cinema.

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Tesla patent aims to improve common on-road complaint

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Image Credit: Met God in Wilderness/YouTube

Tesla is continuing to push the boundaries of vehicle dynamics, as its latest published patent, US12654505B2, or “Suspension Actuator System for a Vehicle,’ which has finally been pushed through.

The design, which is credited to inventors Brian Lee Doorlag, Avraham Kagan, and Justin Sill, introduces a sophisticated hybrid suspension design that blends active motor-driven control with strategic passive elements to deliver superior ride quality, energy efficiency, and resilience against road imperfections, especially potholes.

At the heart of the system is an active control element powered by an electric motor. This motor drives a belt connected to a ball nut assembly and threaded screw, which adjusts the effective length of the suspension strut in real time.

By extending or retracting, the actuator can lift or lower the wheel more accurately, which can end up countering road disturbances. Sensors, including accelerometers and wheel position monitors, feed data to a suspension control system that processes inputs and commands the motor instantly.

This active component doesn’t work alone. A low-rate air spring mounts in parallel with the actuator. Its primary role is to offset much of the vehicle’s static weight, dramatically reducing the power demand on the motor.

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Without this, the active system would constantly fight gravity, draining energy and generating heat. The air spring handles steady-state loads efficiently, allowing the motor to focus on dynamic adjustments.

Complementing this is a series of passive control elementsa spring and an adaptive damper—placed between the actuator and the wheel. This setup filters high-frequency vibrations before they reach the active motor, preventing it from overworking on minor inputs. The adaptive damper, potentially magnetorheological or valve-controlled, further tunes damping electronically for optimal comfort and stability.

How It Differs from Traditional Suspensions

Traditional passive suspensions compromise between comfort and handling, while pure active systems can be power-hungry and complex. Tesla’s hybrid approach resolves this by delegating tasks: the parallel air spring manages weight and low-frequency body motions, the series elements absorb rapid vibrations, and the active actuator tackles larger, lower-frequency events.

The result is a smoother, more isolated cabin experience. High-frequency road noise and harshness diminish, while the vehicle maintains precise control during cornering or acceleration. Energy efficiency improves, too—lower motor loads mean reduced battery drain, potentially extending range in electric vehicles.

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How It Mitigates Potholes Specifically

Potholes are a major challenge because they provide a sudden drop to the wheel plunge, jarring the body of the vehicle, risking damage. The patent explicitly addresses this. Upon detecting a pothole (via sensors or predictive mapping), the control system activates

the motor to retract the strut, effectively pulling the wheel upward to minimize downward excursion. The series spring/damper cushions the impact, while the parallel air spring maintains overall support.

This proactive “wheel retraction” prevents sharp jolts, preserving passenger comfort and protecting components. Integrated with Tesla’s road roughness mapping patents, the system could anticipate potholes from fleet data, enabling preemptive adjustments for even smoother navigation.

Future Implications for Tesla Vehicles

This technology builds on Tesla’s existing adaptive dampers and air suspension that is seen in Cybertruck, but advances toward fully active control. It could roll out to future models, including refreshed Cybertrucks or next-gen vehicles, enhancing both daily drivability and off-road capability. By minimizing power use and complexity, it aligns with Tesla’s goals of efficiency and scalability.

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In summary, US12654505B2 exemplifies Tesla’s engineering philosophy: intelligent integration over brute force. This hybrid suspension promises quieter, more comfortable rides and robust pothole defense, potentially setting a new standard for automotive comfort. As Tesla iterates, drivers can look forward to roads feeling far less rough.

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