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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 just tipped its hand on a major Cybercab feature as production hits Plaid Mode
Tesla has delivered a clear signal that its Robotaxi ambitions are shifting into high gear. On April 17, longtime factory observer and drone pilot Joe Tegtmeyer captured drone footage and still images showing approximately 14 freshly built Cybercabs parked in the outbound lot—each one conspicuously lacking a steering wheel.
Tesla just tipped its hand on a major Cybercab feature as it is putting production into Plaid Mode, but a clear indication of what the company plans to do with the vehicle is now apparent.
Tesla has delivered a clear signal that its Robotaxi ambitions are shifting into high gear, and it’s doing it with full autonomy in mind.
On April 17, longtime factory observer and drone pilot Joe Tegtmeyer captured drone footage and still images showing approximately 14 newly built Cybercabs parked in the outbound lot, each conspicuously lacking a steering wheel, and potentially pedals.
Tegtmeyer’s post highlighted the significance of this development: The images and video reveal sleek, two-seat Cybercabs in their final production form: no driver controls, no side mirrors, and the minimalist interior first unveiled at Tesla’s “We Robot” event in October 2024.
Something big has changed at Giga Texas with Cybercab production … ~ 14 in the outbound lot WITHOUT STEERING WHEELS!
Earlier this week, the production line has begun what we are all waiting for and I would expect to see many more starting on Monday, 4/20 🤠
A big step… pic.twitter.com/K17ZzBlQ8k
— Joe Tegtmeyer 🚀 🤠🛸😎 (@JoeTegtmeyer) April 17, 2026
These units contrast with earlier test vehicles spotted at the factory’s crash-test area, which carried temporary steering wheels and pedals to meet current federal regulations during data-collection phases.
The outbound-lot vehicles appear complete, with production wheels, tire stickers, and the signature Cybercab styling ready for deployment.
This sighting represents a pivotal transition. Tesla designed the Cybercab from the ground up as a purpose-built robotaxi, engineered for unsupervised Full Self-Driving (FSD) operation. Removing manual controls eliminates cost, complexity, and weight while maximizing interior space and range.
The move also signals that Tesla has cleared initial validation hurdles and is now building vehicles to the exact specification intended for commercial robotaxi service.
Industry watchers note the timing aligns with Tesla’s broader rollout plans. Production of early Cybercabs began in late 2025 and early 2026, primarily for internal testing and regulatory compliance.
Federal Motor Vehicle Safety Standards currently limit vehicles without steering wheels to 2,500 units per year without exemption, a cap that Tesla is navigating through ongoing filings.
Tesla Cybercab spotted next to Model Y shows size comparison
The appearance of steering-wheel-free units in the outbound lot suggests the company is preparing a small initial fleet—likely for Austin pilot operations or further validation—while pushing for regulatory relief to scale output.
The development comes as Tesla ramps its dedicated Cybercab line at Gigafactory Texas. If the Monday surge materializes as predicted, observers expect dozens more units to accumulate rapidly.
With unsupervised FSD advancing and regulatory conversations ongoing, these wheel-less Cybercabs parked under the Texas sun represent more than hardware—they embody Tesla’s bet that autonomous mobility is no longer a prototype dream but an imminent reality.
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Tesla preps new Model Y trim for India, a once-elusive market
Tesla’s journey into India began with significant hurdles. For years, the electric vehicle giant faced steep import tariffs ranging from 70 percent to 110 percent on fully built vehicles, which dramatically inflated prices and stalled entry plans.
Tesla is preparing to bring its newest Model Y trim to India, a once-elusive market that was hesitant to allow any vehicles built outside the market into its automotive sector.
Now, it is preparing to allow China-built Model Y vehicles to come into the country, in an effort to expand sales and offer what is a widely-requested variant to Indian customers.
Tesla’s journey into India began with significant hurdles. For years, the electric vehicle giant faced steep import tariffs ranging from 70 percent to 110 percent on fully built vehicles, which dramatically inflated prices and stalled entry plans.
Elon Musk repeatedly criticized these duties as among the world’s highest, making premium EVs like the Model Y prohibitively expensive for most buyers in the price-sensitive market.
After prolonged negotiations and multiple delays, Tesla finally debuted in July 2025 with a quiet rollout focused on luxury segments. It opened showrooms in Mumbai and New Delhi, importing standard Model Y SUVs from its Shanghai Gigafactory.
Tesla China posts strong February wholesale growth at Gigafactory Shanghai
Yet the launch proved challenging: vehicles carried sticker prices near $70,000, leading to tepid demand. Bloomberg reported only about 600 orders in the first two months, while official data showed just 227 registrations for all of 2025—far below internal targets. By early 2026, the company offered discounts of up to ₹200,000 ($2,200) to clear unsold inventory.
Now, less than a year later, Tesla is demonstrating resilience and adaptability. According to a Bloomberg report on April 17, the company is preparing to launch the Model Y L—a six-seat, long-wheelbase variant with three-row seating—as early as next week.
This marks Tesla’s first new product introduction in India since its initial entry. Notably, the newest Model Y configuration, which debuted in China in 2025 and features extended space tailored for families, will once again be exported directly from Tesla’s Shanghai Gigafactory.
The move highlights a shift from early struggles to a more targeted approach, leveraging an existing platform to better suit Indian preferences for multi-generational, spacious SUVs without committing to immediate local production.
Tesla launches in India with Model Y, showing pricing will be biggest challenge
The Model Y L’s arrival underscores Tesla’s incremental strategy amid global EV headwinds and India’s unique challenges, including limited charging infrastructure and competition from local manufacturers.
While tariffs continue to keep pricing in the premium segment, the six-seater variant aims to broaden appeal beyond early luxury adopters by addressing practical family needs.
This evolution, from battling high barriers and disappointing initial sales to exporting its latest derivative model, signals cautious optimism.
Success with the Model Y L could strengthen Tesla’s foothold in one of the world’s most populous markets and potentially pave the way for deeper investments, such as localized manufacturing, should tariff relief or policy shifts materialize.
For now, the China-to-India supply chain represents a pragmatic bridge over the very obstacles that once made entry so difficult.
Elon Musk
Tesla’s golden era is no longer a tagline
Tesla “golden era” teaser video highlights the future of transportation and why car ownership itself may be the next thing to change.
The golden age of autonomous ridesharing is arriving, and Tesla is making sure we can all picture a future that looks like the future. A recent teaser posted to X shows a Cybercab parked outside a home, and with a clear message that your everyday life may soon look like this when the driverless vehicles shows up at your door.
Tesla has begun the rollout of its Robotaxi service across US cities, and the production of its dedicated, fully-autonomous Cybercab vehicle. The first Cybercab rolled off the Giga Texas assembly line on February 17, 2026, with volume production now targeted for this month. Additionally, the Robotaxi service built around it is already running, without human drivers, in US cities.
Tesla Cybercab production ignites with 60 units spotted at Giga Texas
The Cybercab is built without a steering wheel, pedals, or side mirrors, designed from the ground up for unsupervised autonomous operation. Musk described the manufacturing approach as closer to consumer electronics than traditional car production, targeting a cycle time of one unit every ten seconds at full scale.
Drone footage from April 13, 2026 captured over 50 Cybercab units on the Giga Texas campus, with several clustered near the crash testing facility. Musk has noted that Tesla plans to sell the Cybercab to consumers for under $30,000, and owners will be able to add their vehicles to the Tesla robotaxi network when not in personal use, potentially generating income to offset the vehicle’s purchase cost. That model changes the math on vehicle ownership in a meaningful way, making a car something closer to a depreciating asset that can also earn by paying itself off and generate a profit.
During Tesla’s Q4 earnings call, the company confirmed plans to expand the Robotaxi program to seven new cities in the first half of 2026, including Dallas, Houston, Phoenix, Miami, Orlando, Tampa, and Las Vegas. The service already runs without safety drivers in Austin, and public road testing of the Cybercab has expanded to five states, including California, Texas, New York, Illinois, and Massachusetts.
Golden era pic.twitter.com/AS6pX2dK8N
— Tesla Robotaxi (@robotaxi) April 16, 2026
Tesla just tipped its hand on a major Cybercab feature as production hits Plaid Mode
Tesla preps new Model Y trim for India, a once-elusive market
