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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.
- 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)
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Tesla Fremont Factory celebrates 15 years of electric vehicle production
Since opening in 2010, the Fremont Factory has produced all four “S3XY” models while creating tens of thousands of jobs.
Tesla is marking the 15-year anniversary of its Fremont Factory in California, the first automotive mass-manufacturing plant acquired by the electric car maker.
Since opening in 2010, the Fremont Factory has produced all four “S3XY” models while creating tens of thousands of jobs and investing billions of dollars in the region.
Celebrating 15 years of EV production
The Fremont Factory’s milestone was celebrated by the official Tesla Manufacturing account on X, which posted a photo of several Teslas forming a “15” in front of the facility’s iconic white facade. As per the electric vehicle maker, the Fremont Factory has now produced 3.6 million vehicles so far, and it has also created over 20,000 jobs in the state.
“15 years ago, we opened Fremont factory. Today, the Fremont team is producing all 4 S3XY models, totaling 3.6M vehicles made so far. 20k+ California jobs created w/ billions of dollars invested,” the official Tesla Manufacturing account on X wrote in its post.
The Fremont Factory’s transformation
Tesla acquired the Fremont Factory from the defunct NUMMI joint venture between General Motors and Toyota in May 2010 for $42 million. The facility had produced more than 8 million vehicles under GM and Toyota over 26 years. Following its acquisition, Tesla retooled the 5.3-million-square-foot plant to support the production of the Model S sedan.
Over the past 15 years, the factory has evolved into Tesla’s primary North American production hub, assembling the Model S, 3, X, and Y. Annual output has exceeded 550,000 vehicles, including nearly 560,000 produced in 2023 alone. Expectations are high that other products, such as the next-generation Roadster and Optimus, might be produced in the Fremont Factory as well.
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Tesla posts job opening for next-generation Roadster production
Elon Musk teased a major demonstration at the Tesla Design Studio in Hawthorne, scheduled for the end of the year.
Tesla has opened its first job listing specifically for the next-generation Roadster, hinting at some substantial progress on the company’s long-awaited flagship all-electric supercar.
The company is looking for a Manufacturing Engineer to support the development and launch of new battery manufacturing equipment, which would likely be pivotal to the Roaster, considering its teased performance and range.
Tesla’s next-generation Roadster batteries
As per Tesla’s Careers website, the Roadster Manufacturing Engineer’s tasks would include ideating equipment concepts, developing specifications, validating processes, and addressing production bottlenecks. Tesla emphasized that the position involves collaboration across domestic and international sites, supporting equipment factory acceptance tests and assisting operations teams, with expected travel under 50 percent.
“In this role, you will take large-scale manufacturing systems for new battery products and architectures from the early concept development stage through equipment launch, optimization, and handover to local operations teams. Battery development is at the heart of our company, and this is an exciting opportunity to work directly on the central challenges for the all-new Roadster product architecture while still in its early development stages,” the job listing noted.
The opening marks one of the first public hiring efforts explicitly tied to the next-gen Roadster, suggesting that the vehicle’s development might be approaching its initial manufacturing phase. The fact that the new Roadster’s first job opening is related to its battery is interesting, as the vehicle was unveiled with a range of 620 miles way back in late 2018. Though at the time, Elon Musk also noted that the Roadster would be fitted with a 200 kWh battery, twice the size of the batteries used in the Model S and Model X.
Musk teases “most epic demo ever” and fuels Roadster speculation
Back in July, Elon Musk teased a major demonstration at the Tesla Design Studio in Hawthorne, California, scheduled for the end of the year. Musk shared on X that he had just visited the studio, calling the upcoming event the “most epic demo ever by one of year. Ever.”
The statement immediately prompted speculations that Tesla may finally be ready to reveal the production version of the next-generation Roadster. Originally unveiled alongside the Semi in 2018, the Roadster has remained under wraps while the company scaled production of other models. Since its unveiling, however, the Roadster’s rollout has been pushed back in favor of the original Model Y, the refreshed Model S and X, the Cybertruck, the refreshed Model 3, the Semi, and the new Model Y.
At the time of its unveiling, the next-generation Roadster was teased to be nothing short of a monster, with a 0-60 mph time of 1.99 seconds and a top speed of over 250 mph. Elon Musk also teased that the next-generation Roadster would have a range of 620 miles per charge. Later, the CEO noted that the Roadster should be able to achieve a 0-60 mph launch of less than 1 second, thanks to the vehicle’s SpaceX package. Musk has also noted recently that the next-generation Roadster would be “beyond a car.”
News
Tesla’s Shanghai sites now producing massive solar output, confirms exec
Gigafactory Shanghai’s rooftop solar installation now generates an impressive amount of clean energy, and other sites are following suit.
Tesla China Vice President Grace Tao recently shared new details on the company’s solar initiatives in some of its facilities across Shanghai.
In a post on Weibo, the Tesla executive stated that Gigafactory Shanghai’s rooftop solar installation now generates an impressive amount of clean energy, and other sites are following suit.
Tesla China’s rooftop solar initiatives
As per Tao’s post, Giga Shanghai’s rooftop solar system produces about 11 million kWh of electricity per year. This helps reduce carbon emissions by an estimated 4,600 tons annually.
The Shanghai Megafactory, which produces Megapack batteries, is also being fitted with solar panels. Once operational, it is expected to generate an additional 6 million kWh per year and further lower carbon emissions by roughly 2,500 tons.
“At present, the roof of the Shanghai Super Factory is covered with photovoltaic panels, which can generate 11 million kWh of electricity annually and reduce carbon emissions by 4,600 tons. The Shanghai Energy Storage Super Factory next door is also installing photovoltaic panels, which is expected to generate an additional 6 million kWh a year and reduce carbon emissions by 2,500 tons,” Tao wrote in her post.
Tesla expands solar and storage efforts
Beyond its manufacturing hubs, Tesla is extending its renewable energy strategy to service centers and retail operations in China. Tao stated that the roof of Tesla’s Shanghai Kangqiao Direct Body and Paint Center already produces around 400,000 kWh of green electricity each year, reducing emissions by yet another 170 tons.
She highlighted that Tesla’s goal is to ensure clean electricity powers the full lifecycle of its products, from manufacturing and storage to on-road charging. “The manufacture, storage, and use of clean electricity runs through the entire chain of Tesla products, and is also the contribution of every Tesla owner to a sustainable tomorrow for the earth,” Tao stated.
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