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Ex-SpaceX engineer leads Stratolaunch to major rocket engine test milestone
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.
The team made amazing progress this week! Check out the #PGAEngine preburner’s first hot-fire test at @NASAStennis. #NewUSEngine pic.twitter.com/kKTnf0bj1S
— Stratolaunch (@Stratolaunch) November 6, 2018
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.
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- A to-scale comparison of Falcon 1, Pegasus XL, MLV, and Falcon 9. (Teslarati/Stratolaunch/Wikipedia)
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- A render of Stratolaunch’s impressive PGA engine. Note the giant nozzle relative to the throat. (Stratolaunch)
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.
“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.
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- PGA’s first full-scale preburner seen during assembly. (Stratolaunch)
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- PGA’s first full-scale preburner seen during assembly. (Stratolaunch)
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- Jeff Thornburg stands in front of Stratolaunch’s NASA Stennis Space Center test stand. (Stratolaunch)
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- The PGA preburner seen after installation at Stennis. (Stratolaunch)
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- The control center. (Stratolaunch)
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- MLV is released from Stratolauncher. (Stratolaunch)
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- A concept video produced by Stratolaunch shows the Roc launching a Kraken rocket. (Stratolaunch, via Wired)
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Tesla parked 50+ Cybercabs outside its Texas Factory with some crash tested
Dozens of Tesla Cybercabs have been spotted at Giga Texas crash testing facility ahead of launch.
Drone footage captured by longtime Giga Texas observer Joe Tegtmeyer shows over 50 units of Tesla Cybercab at the Austin factory campus, including several units clustered by Tesla’s on-site crash testing facility.
The outbound lot at Gigafactory Texas sits just outside the factory exit and serves as the primary staging area where finished vehicles are held before being loaded onto transport carriers or dispatched for validation testing. On any given day, the lot holds a mix of Model Y and Cybertruck units alongside the growing Tesla Cybercab fleet, as can be seen in the drone footage captured by Joe Tegtmeyer.
Tesla Cybercab fleet spotted at Gigafactory Texas on April 13, 2026 [Credit: Joe Tegtmeyer)
Tesla Cybercab fleet spotted at Gigafactory Texas [Credit: Joe Tegtmeyer)
Tesla Cybercab crash test units spotted at Gigafactory Texas [Credit: Joe Tegtmeyer)
Tesla announced its Spring 2026 software update, and it’s the most feature-dense seasonal release the company has put out. The update covers twelve named changes spanning FSD, voice AI, safety lighting, dashcam storage, and pet display customization, among other things.
The centerpiece for owners with AI4 hardware is a redesigned Self-Driving app. The new interface lets owners subscribe to Full Self-Driving with a single tap and view ongoing FSD usage stats directly in the vehicle.
Grok gets its biggest in-car upgrade yet. The update adds a “Hey Grok” hands-free wake word along with location-based reminders, so a driver can now say “remind me to pick up groceries when I get home” without touching the screen. Grok first arrived in vehicles in July 2025, but each update has pushed it closer to genuine daily utility. Musk framed the broader vision clearly at Davos in January, saying Tesla is “really moving into a future that is based on autonomy.”
On safety, the update introduces enhanced blind spot warning lights that integrate directly with the cabin’s ambient lighting, building on the blind spot door warning that arrived in update 2026.8.
Dog Mode has been renamed Pet Mode and now lets owners choose a dog, cat, or hedgehog icon and add their pet’s name to the display.
Dashcam retention now extends up to 24 hours, up from the previous one-hour rolling loop, with a permanent save option for any clip. Weather maps now show rain and snow with better color differentiation and include the past hour of precipitation data along the route.
Tesla has now established a clear rhythm of two major OTA pushes per year. As with last year’s Spring update, that cycle started taking shape in 2025 with adaptive headlights and trunk customization. The 2025 Holiday Update then added Grok to the vehicle for the first time. This Spring follows that structure: the Holiday update introduces new architecture, and the Spring update broadens it across the fleet.
Two notable features still did not make it. IFTTT automations, which launched in China earlier this year, were held back from this North American release for unknown reasons, and Apple CarPlay remains absent, reportedly still delayed by iOS 26 and Apple Maps compatibility issues.
Below is the full list of feature updates released by Tesla.
— Tesla (@Tesla) April 13, 2026
News
Tesla launches new Model Y interior option
Produced at Gigafactory Shanghai, the update applies to all five-seat Premium Model Y configurations and started being seen on customer deliveries this week. The move marks the first major interior refresh for the compact crossover since its global debut.
Tesla has rolled out a striking new interior choice for its best-selling Model Y in China, replacing the long-familiar white cabin with a fresh option: Zen Grey.
Produced at Gigafactory Shanghai, the update applies to all five-seat Premium Model Y configurations and started being seen on customer deliveries this week. The move marks the first major interior refresh for the compact crossover since its global debut.
The Zen Grey interior swaps the classic black-and-white contrast for a softer, more unified palette. Seats, door panels, and center console trim now feature a warm light-grey tone that covers far more surface area than before.
Previously, black accents on the console, door handles, and lower dashboard are now color-matched in the same pebbled vegan leather, creating a brighter, less clinical cabin.
Tesla describes the material as durable and easy to maintain while delivering a noticeably more premium feel. Early photos and videos from Chinese owners show the new shade reflecting natural light beautifully, giving the spacious Model Y an even airier, more inviting atmosphere without sacrificing the minimalist design customers expect:
🚨 First look at Tesla’s new Zen Grey interior, which differs slightly in tone and in placement compared to the now discontinued White Interior https://t.co/rRRuEOrbm4 pic.twitter.com/p7uyNfO3xY
— TESLARATI (@Teslarati) April 13, 2026
The change is not an added-cost upgrade but a direct replacement for the discontinued white interior on Shanghai-built vehicles. Customers configuring a new Model Y in China, Hong Kong, or Macau now see Zen Grey as the default light-colored choice.
The update also flows to export markets supplied by Giga Shanghai, including Australia, New Zealand, South Korea, Japan, and the Philippines. Tesla has used its Chinese factory as an innovation hub before, and executives appear to be testing broader appeal with this subtler, warmer tone that avoids the high-maintenance reputation sometimes associated with bright white leather.
Beyond the interior, the refreshed Model Y from Shanghai includes minor exterior tweaks such as blacked-out badges on some trims and optional dark 20-inch wheels.
These changes arrive as Tesla faces stiff competition from domestic EV makers in its largest market. By refreshing the Model Y’s cabin without raising prices, the company is signaling continued commitment to value and constant improvement.
With over 1.2 million Model Y units already on Chinese roads, the Zen Grey launch gives existing owners a fresh talking point and new buyers another reason to choose Tesla. As deliveries ramp up this month, the updated interior is expected to become the dominant light-colored choice across the Asia-Pacific region.
Tesla has not yet confirmed whether the Zen Grey will reach Fremont, Austin, or Berlin-built Model Ys, but Shanghai’s track record suggests the option could spread quickly if customer feedback remains strong.
Tesla parked 50+ Cybercabs outside its Texas Factory with some crash tested
Tesla 2026 Spring Update drops 12 new features owners have been waiting for
