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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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News
Tesla Europe builds momentum with expanding FSD demos and regional launches
Needless to say, it appears that Tesla is putting in some serious effort into boosting sales in Europe this year.
Tesla has been notably active across Europe in recent weeks, expanding its Full Self-Driving (Supervised) ride-along program, entering a new market, and showcasing its newest vehicles across multiple regions.
Needless to say, it appears that Tesla is putting in some serious effort into boosting sales in Europe this year.
Tesla Europe recently announced the expansion of its FSD (Supervised) ride-along experiences, inviting the public to experience the system on local roads. Initially available in Italy, France, and Germany when it launched, the program has now expanded to Hungary, Finland, and Spain.
The ride-along program allows participants to ride in the passenger seat and observe how FSD Supervised handles real-world traffic scenarios, including dense urban driving and other challenging conditions. Tesla has positioned the initiative as a way to familiarize European drivers and regulators with the system’s capabilities in everyday use. The program has received positive reviews so far, with many being impressed by FSD’s real-world capabilities.
Tesla also recently launched operations in Slovakia with a pop-up store and multi-day public event in Bratislava, as noted in an EV Wire report. The launch, held from January 16 to 18 at the Eurovea Mall Promenade, featured test drives, vehicle displays, including the Cybertruck, as well as family-focused attractions such as a mini-Tesla racetrack.
Local observers noted that Tesla Optimus was also shown at the event, while the Tesla Owners Slovakia club welcomed the brand with a coordinated light show near the Slovak National Theater. Tesla Europe later shared its appreciation for Slovakia in a post on its official social media account on X, stating, “Thanks, Slovakia, for the amazing last 3 days & for giving us such a warm welcome!”
Tesla’s Slovakia entry follows a familiar pattern used by the company in other European markets. Tesla opened a pop-up store in Bratislava as an initial step, with plans for a permanent showroom and a potential service center at a renovated site previously occupied by a Jeep and Dodge dealership. Tesla has used a similar approach in markets such as Czechia and Lithuania, where permanent facilities followed within a few months of pop-up launches.
Slovakia already has six Supercharging sites totaling 46 Superchargers, including two locations in Bratislava, providing early infrastructure support for Tesla owners. Tesla staff program manager Supratik Saha described the Slovakia launch as a strategic expansion in the heart of the EU, citing the country’s strong automotive manufacturing base and appetite for advanced technology.
Beyond the EU, the company also marked another milestone with the first Cybertruck deliveries in the United Arab Emirates, signaling continued geographic expansion for Tesla’s newest vehicle. Just like Tesla Slovakia, the Cybertruck also received a warm welcome from the UAE’s EV community.
News
Tesla Sweden maintains Trelleborg port deal despite union blockade
As noted in a report from Dagens Arbete (DA), Tesla was able to maintain its storage agreement with the Port of Trelleborg.
Tesla Sweden is still storing vehicles at the Port of Trelleborg despite the ongoing blockades against the company from the country’s labor unions.
Tesla still at Port of Trelleborg
As noted in a report from Dagens Arbete (DA), Tesla was able to maintain its storage agreement with the Port of Trelleborg. This allows the company to keep vehicles at the port while imports into Sweden continue. This was despite the Transport Workers’ Union’s blockade, which was aimed at halting the loading and unloading of Tesla vehicles in the area.
Local union leader Jörgen Wärja, chairman of Transport and an employee representative on the port company’s board, confirmed that the agreement was still active. “The agreement has not been terminated. You want to have the money instead of having empty warehouses. I understand the reason, but I do not support it,” Wärja said
The local union leader also noted that he visited Tesla’s storage area earlier this week. “There were a lot of cars. I was surprised that there were so many, actually,” he said.
Tesla had been able to bring vehicles into Sweden via passenger ferries at Trelleborg, a method that unions said allowed the company to bypass the blockade, DA noted. According to estimates from IF Metall, the workaround enabled Tesla to deliver thousands of cars to Sweden each year.
Port defends decision
The Port of Trelleborg did not issue a comment on its current agreement with Tesla, but said it had complied with union sympathy measures. Documents reviewed by Swedish media showed that the contract with Tesla was being extended in six-month intervals.
Port CEO Malin Collin noted that the port would not discuss individual customer arrangements. “We do not go into details regarding any customer agreements. We have continuous dialogue with potential tenants, and this is not unique to any location,” Collin wrote in an email.
The CEO added that the port was following legal requirements related to the labor dispute. “We have taken note of the Transport Workers’ Union’s decision on sympathy measures and are of course following applicable legislation and the requirements placed on us as employers,” Collin said.
Jörgen Wärja, for his part, stated that the issue was not whether Tesla’s imports into Sweden could be fully stopped, but whether the port should provide logistical support to the electric vehicle maker during an active conflict. “The port shouldn’t have anything to do with Tesla at all, we believe,” he said. “It’s purely moral. Whether you honor a conflict or not. If you say you support Transport’s sympathetic actions against Tesla, it becomes a double standard.”
Elon Musk
Elon Musk shares insights on SpaceX and Tesla’s potential scale
In a pair of recent posts on X, Musk argued that both companies operate in domains where growth is not linear, but exponential.
Elon Musk outlined why he believes Tesla and SpaceX ultimately dwarf their competitors, pointing to autonomy, robotics, and space-based energy as forces that fundamentally reshape economic scale.
In a pair of recent posts on X, Musk argued that both companies operate in domains where growth is not linear, but exponential.
Space-based energy
In a response to a user on X who observed that SpaceX has a larger valuation than all six US defense companies combined, Musk explained that space-based industries will eventually surpass the total economic value of Earth. He noted that space allows humanity to harness roughly 100,000 times more energy than Earth currently uses, while still consuming less than a millionth of the Sun’s total energy output.
That level of available energy should enable the emergence and development of industries that are simply not possible within Earth’s physical and environmental constraints. Continuous solar exposure in space, as per Musk’s comment, removes limitations imposed by atmosphere, weather, and land availability.
Autonomy and robots
In a follow-up post, Elon Musk explaned that “due to autonomy, Tesla is worth more than the rest of the auto industry.” Musk added that this assessment does not yet account for Optimus, Tesla’s humanoid robot. As per the CEO, once Optimus reaches scaled production, it could increase Earth’s gross domestic product by an order of magnitude, ultimately paving the way for sustainable abundance.
Even before the advent of Optimus, however, Tesla’s autonomous driving system already gives vehicles the option to become revenue-generating assets through services like the Tesla Robotaxi network. Tesla’s autonomous efforts seem to be on the verge of paying off, as services like the Robotaxi network have already been launched in its initial stages in Austin and the Bay Area.
Tesla Europe builds momentum with expanding FSD demos and regional launches
Tesla Sweden maintains Trelleborg port deal despite union blockade
