News
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.
-
- A to-scale comparison of Falcon 1, Pegasus XL, MLV, and Falcon 9. (Teslarati/Stratolaunch/Wikipedia)
-
- 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.
-
- PGA’s first full-scale preburner seen during assembly. (Stratolaunch)
-
- PGA’s first full-scale preburner seen during assembly. (Stratolaunch)
-
- Jeff Thornburg stands in front of Stratolaunch’s NASA Stennis Space Center test stand. (Stratolaunch)
-
- The PGA preburner seen after installation at Stennis. (Stratolaunch)
-
- The control center. (Stratolaunch)
-
- MLV is released from Stratolauncher. (Stratolaunch)
-
- A concept video produced by Stratolaunch shows the Roc launching a Kraken rocket. (Stratolaunch, via Wired)
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!
News
Tesla Model 3 and Model Y dominates U.S. EV market in 2025
The figures were detailed in Kelley Blue Book’s Q4 2025 U.S. Electric Vehicle Sales Report.
Tesla’s Model 3 and Model Y continued to overwhelmingly dominate the United States’ electric vehicle market in 2025. New sales data showed that Tesla’s two mass market cars maintained a commanding segment share, with the Model 3 posting year-to-date growth and the Model Y remaining resilient despite factory shutdowns tied to its refresh.
The figures were detailed in Kelley Blue Book’s Q4 2025 U.S. Electric Vehicle Sales Report.
Model 3 and Model Y are still dominant
According to the report, Tesla delivered an estimated 192,440 Model 3 sedans in the United States in 2025, representing a 1.3% year-to-date increase compared to 2024. The Model 3 alone accounted for 15.9% of all U.S. EV sales, making it one of the highest-volume electric vehicles in the country.
The Model Y was even more dominant. U.S. deliveries of the all-electric crossover reached 357,528 units in 2025, a 4.0% year-to-date decline from the prior year. It should be noted, however, that the drop came during a year that included production shutdowns at Tesla’s Fremont Factory and Gigafactory Texas as the company transitioned to the new Model Y. Even with those disruptions, the Model Y captured an overwhelming 39.5% share of the market, far surpassing any single competitor.
Combined, the Model 3 and Model Y represented more than half of all EVs sold in the United States during 2025, highlighting Tesla’s iron grip on the country’s mass-market EV segment.
Tesla’s challenges in 2025
Tesla’s sustained performance came amid a year of elevated public and political controversy surrounding Elon Musk, whose political activities in the first half of the year ended up fueling a narrative that the CEO’s actions are damaging the automaker’s consumer appeal. However, U.S. sales data suggest that demand for Tesla’s core vehicles has remained remarkably resilient.
Based on Kelley Blue Book’s Q4 2025 U.S. Electric Vehicle Sales Report, Tesla’s most expensive offerings such as the Tesla Cybertruck, Model S, and Model X, all saw steep declines in 2025. This suggests that mainstream EV buyers might have had a price issue with Tesla’s more expensive offerings, not an Elon Musk issue.
Ultimately, despite broader EV market softness, with total U.S. EV sales slipping about 2% year-to-date, Tesla still accounted for 58.9% of all EV deliveries in 2025, according to the report. This means that out of every ten EVs sold in the United States in 2025, more than half of them were Teslas.
News
Tesla Model 3 and Model Y earn Euro NCAP Best in Class safety awards
“The company’s best-selling Model Y proved the gold standard for small SUVs,” Euro NCAP noted.
Tesla won dual categories in the Euro NCAP Best in Class awards, with the Model 3 being named the safest Large Family Car and the Model Y being recognized as the safest Small SUV.
The feat was highlighted by Tesla Europe & Middle East in a post on its official account on social media platform X.
Model 3 and Model Y lead their respective segments
As per a press release from the Euro NCAP, the organization’s Best in Class designation is based on a weighted assessment of four key areas: Adult Occupant, Child Occupant, Vulnerable Road User, and Safety Assist. Only vehicles that achieved a 5-star Euro NCAP rating and were evaluated with standard safety equipment are eligible for the award.
Euro NCAP noted that the updated Tesla Model 3 performed particularly well in Child Occupant protection, while its Safety Assist score reflected Tesla’s ongoing improvements to driver-assistance systems. The Model Y similarly stood out in Child Occupant protection and Safety Assist, reinforcing Tesla’s dual-category win.
“The company’s best-selling Model Y proved the gold standard for small SUVs,” Euro NCAP noted.
Euro NCAP leadership shares insights
Euro NCAP Secretary General Dr. Michiel van Ratingen said the organization’s Best in Class awards are designed to help consumers identify the safest vehicles over the past year.
Van Ratingen noted that 2025 was Euro NCAP’s busiest year to date, with more vehicles tested than ever before, amid a growing variety of electric cars and increasingly sophisticated safety systems. While the Mercedes-Benz CLA ultimately earned the title of Best Performer of 2025, he emphasized that Tesla finished only fractionally behind in the overall rankings.
“It was a close-run competition,” van Ratingen said. “Tesla was only fractionally behind, and new entrants like firefly and Leapmotor show how global competition continues to grow, which can only be a good thing for consumers who value safety as much as style, practicality, driving performance, and running costs from their next car.”
News
Tesla is shifting FSD to a subscription-only model, confirms Elon Musk
Tesla CEO Elon Musk confirmed the upcoming update in a post on social media platform X.
Tesla will be ending one-time purchases of its Full Self-Driving (FSD) system after Valentine’s Day, transitioning the feature to a monthly subscription-only model.
Tesla CEO Elon Musk confirmed the upcoming update in a post on social media platform X.
No more FSD one-time purchases
As per Elon Musk in his post on X, “Tesla will stop selling FSD after Feb 14. FSD will only be available as a monthly subscription thereafter.” This marks a shift in how Tesla monetizes its FSD system, which can now be purchased for a one-time fee or accessed through a monthly subscription.
FSD’s subscription model has been $99 per month in the United States, while its one-time purchase option is currently priced at $8,000. FSD’s one-time purchase price has swung wildly in recent years, reaching $15,000 in September 2022. At the time, FSD was proficient, but its performance was not on par with v14. This made its $15,000 upfront price a hard sell for consumers.
Tesla’s move to a subscription-only model could then streamline how the company sells FSD. It also lowers the entry price for the system, as even price-conscious drivers would likely be able to justify FSD’s $99 monthly subscription cost during periods when long-distance travel is prevalent, like the holidays.
Musk’s compensation plan and FSD subscription targets
Tesla’s shift to a subscription-only FSD model comes amidst Musk’s 2025 CEO Performance Award, which was approved by Tesla shareholders at the 2025 Annual Shareholders Meeting with roughly 75% support. Under the long-term compensation plan, Musk must achieve a series of ambitious operational milestones, including 10 million active FSD subscriptions, over the next decade for his stock awards to vest.
The 2025 CEO Performance Award’s structure ties Musk’s potential compensation to Tesla’s aggressive targets that span market capitalization, vehicle deliveries, robotics, and software adoption. Apart from his 10-million active FSD subscription target, Musk’s compensation is also tied to Tesla producing 20 million vehicles cumulatively, delivering 1 million Tesla bots, and having 1 million Robotaxis in operation. He must also lead Tesla to a market cap of $8.5 trillion.
If successful, Elon Musk’s 2025 CEO Performance Award could make him the world’s first trillionaire. It could also help Tesla become the world’s most valuable company by market cap by a notable margin.
Tesla Model 3 and Model Y dominates U.S. EV market in 2025
Tesla Model 3 and Model Y earn Euro NCAP Best in Class safety awards
