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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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Energy

Zuckerberg’s Meta taps Musk’s Tesla for massive clean energy project

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Credit: Tesla

In a notable intersection of Big Tech powerhouses, Meta, led by Mark Zuckerberg, has partnered with Canadian energy infrastructure giant Enbridge on a significant renewable energy initiative that will rely on battery technology from Elon Musk’s Tesla.

The project, which was announced this week, marks another step in Meta’s aggressive push to power its expanding data center operations with clean energy, dispelling many of the complaints people have about them.

This new development is located near Cheyenne, Wyoming, and will feature a 365-megawatt (MW) solar farm paired with a 200 MW/1,600 megawatt-hour (MWh) battery energy storage system, also known as BESS. Tesla is providing the batteries for the project, valued at roughly $200 million.

The story was originally reported by Utility Dive.

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This Wyoming project represents the first phase of Enbridge and Meta’s joint “Cowboy Project.” Once operational, it will deliver power to Meta’s regional data centers through Cheyenne Light, Fuel, and Power under Wyoming’s Large Power Contract Service tariff.

This tariff, originally developed in collaboration with Microsoft and Black Hills Energy, is designed specifically for large loads like data centers. It ensures that the renewable supply serves hyperscale customers without impacting retail electricity rates for other users.

The battery system will operate under a long-term tolling agreement, providing dispatchable capacity that enhances grid reliability. During periods of high demand, the utility can access the backup generation, addressing one of the key challenges of integrating large-scale renewables with the explosive growth of data center electricity demand driven by artificial intelligence.

This latest collaboration builds on prior joint efforts between Enbridge and Meta in Texas, including the 600 MW Clear Fork Solar, 152 MW Easter Wind, and 300 MW Cone Wind projects. Together with the Wyoming initiative, the companies have now partnered on roughly 1.6 gigawatts (GW) of combined solar, wind, and storage capacity.

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The deal highlights the intensifying demand for reliable, low-carbon power from technology giants. Meta has committed to supporting its data center growth with renewable energy, joining peers like Microsoft and Google in seeking large-scale solutions. Enbridge’s Allen Capps described the project as “one of the larger utility-scale battery installations supporting U.S. data center operations and growth.”

The involvement of Tesla’s battery technology adds an intriguing layer, linking two of the world’s most prominent tech leaders—Zuckerberg and Musk—in the clean energy transition.

As data centers continue to drive unprecedented electricity load growth across the United States, projects like this one illustrate how hyperscalers are turning to strategic partnerships with traditional energy players and innovative storage solutions to meet both sustainability goals and reliability needs.

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SpaceX reveals reason for Starship v3 stand down, announces next launch date

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Credit: SpaceX

SpaceX has decided to stand down from what was supposed to be the first test launch of Starship’s v3 rocket tonight after a minor issue with a hydraulic pin delayed the flight once more.

The company scrubbed its first test flight of the upgraded Starship v3 on May 21 in the final minutes of the countdown. SpaceX CEO Elon Musk quickly took to social media platform X, explaining that a hydraulic pin on the launch tower’s “chopsticks” arm failed to retract properly.

Musk added that the company would fix the issue this evening. SpaceX will attempt another launch tomorrow night at 5:30 p.m. CT, 6:30 p.m. ET, and 3:30 p.m. PT.

The countdown for Starship Flight 12 — featuring the taller and more capable V3 stack with Booster 19 and Ship 39 — had been progressing smoothly until the late-stage issue surfaced. The Mechazilla tower arm, designed to secure the vehicle on the pad and eventually catch returning boosters, could not complete its retraction sequence.

SpaceX teams immediately began troubleshooting the hydraulic system for an overnight repair.

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Starship V3 introduces several significant upgrades over earlier versions. These include greater propellant capacity, more powerful Raptor 3 engines, larger grid fins, enhanced heat shielding, and an improved fuel transfer system.

We covered the changes that were announced just days ago by SpaceX:

SpaceX unveils sweeping Starship V3 upgrades ahead of May 19 launch

The changes are intended to increase payload performance, support higher flight rates, and advance the vehicle toward operational missions, including Starlink deployments, NASA Artemis lunar landings, and future crewed Mars flights. The debut flight from Starbase’s new Launch Pad 2 marked an important milestone in scaling up the fully reusable Starship system.

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This stand-down highlights the intricate challenges of preparing the world’s most powerful rocket for flight. Despite extensive pre-launch checks, a single component in the ground support equipment can force a scrub.

The incident aligns with Starship’s proven iterative development approach. Previous test flights have encountered both successes and setbacks, each providing critical data that refines hardware and procedures. Some outlets may call some of these flights “failures,” when in reality, they are all opportunities for SpaceX to learn for the next attempt.

With V3, SpaceX aims to reduce ground-system dependencies and increase launch cadence to meet ambitious long-term goals.

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Tesla Model Y becomes first-ever car to reach legendary milestone

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Credit: Tesla Manufacturing

The Tesla Model Y became the first-ever car to reach a legendary Norwegian milestone, surpassing 100,000 new registrations after gaining a reputation as one of the most popular vehicles in the country and the world.

As of May 20, Norwegian authorities have registered 100,224 units of the electric SUV, according to data from local outlet Opplysningsrådet for veitrafikken (OFV).

By population, roughly one in every 29 passenger cars on Norwegian roads is now a Model Y, underscoring its rapid rise as a national favorite.

Since the first deliveries in August 2021, the Model Y has transformed from a newcomer to a staple in Norwegian traffic.

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Tesla back on top as Norway’s EV market surges to 98% share in February

Geir Inge Stokke, the Managing Director of OFV, described the achievement as “remarkable,” noting that few single models have gained such traction so quickly. “Tesla Model Y has hit the Norwegian market spot on, and the numbers illustrate how fast the EV market has developed here,” Stokke said.

The Model Y’s success reflects Norway’s aggressive push toward electrification. Nearly nine out of ten units, 87.6 percent, to be exact, are privately registered, with the remaining 12.4 percent on company plates. Owners span the country, from major cities to smaller municipalities, proving it is no longer just an urban or niche vehicle but a true “people’s car.

Who is Buying Tesla Model Ys in Norway?

Typical Model Y drivers are men in their early 40s. The average registered user age is 44, with 83 percent male and 17 percent female. Stokke noted that household usage often extends beyond the primary registrant, broadening the vehicle’s real-world appeal.

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Geographically, adoption concentrates in urban centers with strong charging infrastructure. Oslo leads with 16,861 registrations (16.82 percent of the national total), followed by Bergen (7,450), Bærum (4,313), and Trondheim (4,240).

The top five municipalities—Oslo, Bergen, Bærum, Trondheim, and Asker—account for 35,463 units, or about 35 percent of all Model Ys. Yet the vehicle’s presence outside big cities highlights its broad acceptance.

Growth Trajectory and Popularity

Tesla built a lot of sales momentum in a short amount of time. In 2021, registrations closed out at 8,267, but more than doubled to more than 17,000 units in 2022 and more than 23,000 units in 2023. 2025 was the company’s strongest year yet, as Tesla managed to record 27,621 registrations.

Through 2026, Tesla already has 7,036 registrations.

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Tesla’s Global Success with the Model Y

Tesla has tasted so much success with the Model Y; it has been the best-selling car in the world three times, it has dominated EV sales in numerous countries, and contributed to a mass adoption of electric vehicles across the planet.

As Stokke emphasized, the Model Y’s journey from newcomer to icon mirrors Norway’s broader success story. With robust incentives that push sales, excellent infrastructure, and consumer eagerness to transition to sustainable powertrains, the country continues setting global benchmarks in sustainable mobility.

The Tesla Model Y stands as a shining example of how quickly change can happen when conditions align.

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