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.
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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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Elon Musk
Brazil Supreme Court orders Elon Musk and X investigation closed
The decision was issued by Supreme Court Justice Alexandre de Moraes following a recommendation from Brazil’s Prosecutor-General Paulo Gonet.
Brazil’s Supreme Federal Court has ordered the closure of an investigation involving Elon Musk and social media platform X. The inquiry had been pending for about two years and examined whether the platform was used to coordinate attacks against members of the judiciary.
The decision was issued by Supreme Court Justice Alexandre de Moraes following a recommendation from Brazil’s Prosecutor-General Paulo Gonet.
According to a report from Agencia Brasil, the investigation conducted by the Federal Police did not find evidence that X deliberately attempted to attack the judiciary or circumvent court orders.
Prosecutor-General Paulo Gonet concluded that the irregularities identified during the probe did not indicate fraudulent intent.
Justice Moraes accepted the prosecutor’s recommendation and ruled that the investigation should be closed. Under the ruling, the case will remain closed unless new evidence emerges.
The inquiry stemmed from concerns that content on X may have enabled online attacks against Supreme Court justices or violated rulings requiring the suspension of certain accounts under investigation.
Justice Moraes had previously taken several enforcement actions related to the platform during the broader dispute involving social media regulation in Brazil.
These included ordering a nationwide block of the platform, freezing Starlink accounts, and imposing fines on X totaling about $5.2 million. Authorities also froze financial assets linked to X and SpaceX through Starlink to collect unpaid penalties and seized roughly $3.3 million from the companies’ accounts.
Moraes also imposed daily fines of up to R$5 million, about $920,000, for alleged evasion of the X ban and established penalties of R$50,000 per day for VPN users who attempted to bypass the restriction.
Brazil remains an important market for X, with roughly 17 million users, making it one of the platform’s larger user bases globally.
The country is also a major market for Starlink, SpaceX’s satellite internet service, which has surpassed one million subscribers in Brazil.
Elon Musk
FCC chair criticizes Amazon over opposition to SpaceX satellite plan
Carr made the remarks in a post on social media platform X.
U.S. Federal Communications Commission (FCC) Chairman Brendan Carr criticized Amazon after the company opposed SpaceX’s proposal to launch a large satellite constellation that could function as an orbital data center network.
Carr made the remarks in a post on social media platform X.
Amazon recently urged the FCC to reject SpaceX’s application to deploy a constellation of up to 1 million low Earth orbit satellites that could serve as artificial intelligence data centers in space.
The company described the proposal as a “lofty ambition rather than a real plan,” arguing that SpaceX had not provided sufficient details about how the system would operate.
Carr responded by pointing to Amazon’s own satellite deployment progress.
“Amazon should focus on the fact that it will fall roughly 1,000 satellites short of meeting its upcoming deployment milestone, rather than spending their time and resources filing petitions against companies that are putting thousands of satellites in orbit,” Carr wrote on X.
Amazon has declined to comment on the statement.
Amazon has been working to deploy its Project Kuiper satellite network, which is intended to compete with SpaceX’s Starlink service. The company has invested more than $10 billion in the program and has launched more than 200 satellites since April of last year.
Amazon has also asked the FCC for a 24-month extension, until July 2028, to meet a requirement to deploy roughly 1,600 satellites by July 2026, as noted in a CNBC report.
SpaceX’s Starlink network currently has nearly 10,000 satellites in orbit and serves roughly 10 million customers. The FCC has also authorized SpaceX to deploy 7,500 additional satellites as the company continues expanding its global satellite internet network.
Energy
Tesla Energy gains UK license to sell electricity to homes and businesses
The license was granted to Tesla Energy Ventures Ltd. by UK energy regulator Ofgem after a seven-month review process.
Tesla Energy has received a license to supply electricity in the United Kingdom, opening the door for the company to serve homes and businesses in the country.
The license was granted to Tesla Energy Ventures Ltd. by UK energy regulator Ofgem after a seven-month review process.
According to Ofgem, the license took effect at 6 p.m. local time on Wednesday and applies to Great Britain.
The approval allows Tesla’s energy business to sell electricity directly to customers in the region, as noted in a Bloomberg News report.
Tesla has already expanded similar services in the United States. In Texas, the company offers electricity plans that allow Tesla owners to charge their vehicles at a lower cost while also feeding excess electricity back into the grid.
Tesla already has a sizable presence in the UK market. According to price comparison website U-switch, there are more than 250,000 Tesla electric vehicles in the country and thousands of Tesla home energy storage systems.
Ofgem also noted that Tesla Motors Ltd., a separate entity incorporated in England and Wales, received an electricity generation license in June 2020.
The new UK license arrives as Tesla continues expanding its global energy business.
Last year, Tesla Energy retained the top position in the global battery energy storage system (BESS) integrator market for the second consecutive year. According to Wood Mackenzie’s latest rankings, Tesla held about 15% of global market share in 2024.
The company also maintained a dominant position in North America, where it captured roughly 39% market share in the region.
At the same time, competition in the energy storage sector is increasing. Chinese companies such as Sungrow have been expanding their presence globally, particularly in Europe.
Brazil Supreme Court orders Elon Musk and X investigation closed
FCC chair criticizes Amazon over opposition to SpaceX satellite plan
