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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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Tesla Robotaxi appears to be heading to a new U.S. city
Things are expanding for Robotaxi, but the big sign that it is really moving along greatly will be with the expansion to a new city. Tesla has not gone outside of Austin or the Bay Area as of yet, and launching in a new city will be a great indicator of progress.
Tesla Robotaxi appears to be heading to a new U.S. city, and although the company has revealed plans to launch in six new metros this year, it has yet to establish a new location outside of Austin and the Bay Area of California, where it has operated since last Summer.
A lot full of Model Y vehicles was spotted in Henderson, a town just north of Las Vegas, but there seems to be more than just this hint indicating that the Sin City will be the next location to offer potentially driverless rides in a Tesla using its Full Self-Driving suite.
These Model Ys are not your typical vehicles, as they are fitted with hardware that is only on Robotaxis: a rear camera washer is the dead giveaway:
🚨 These rear camera washers are only present on Robotaxi vehicles
Maybe Las Vegas is the next city to get the Robotaxi suite 😀 https://t.co/my3da5L4zc pic.twitter.com/jYFQuX1j2E
— TESLARATI (@Teslarati) March 17, 2026
The photos and video of the lot were taken by TheZacher on X, who spotted the Model Y fleet in the Henderson parking lot.
The rear camera washer is the main piece of evidence here that indicates Tesla could be looking to expand Robotaxi to Las Vegas, a major ride-hailing hot spot, as it is one of the biggest tourist attractions in the United States. Ride-sharing is a major industry in Vegas, especially for those who are staying off the Strip.
Tesla has also been extremely transparent that Vegas is on its radar for the Robotaxi fleet, as it revealed last year that it was one of five new U.S. cities that it planned to launch the ride-hailing service in this year.
Tesla confirms Robotaxi is heading to five new cities in the U.S.
The others were Phoenix, Dallas, Houston, and Miami.
Things are expanding for Robotaxi, but the big sign that it is really moving along greatly will be with the expansion to a new city. Tesla has not gone outside of Austin or the Bay Area as of yet, and launching in a new city will be a great indicator of progress.
It will also give Tesla a new benchmark against rival company Waymo, which has operated in Las Vegas for some time.
News
Tesla Roadster gets new unveiling date once again
Musk announced last year that the unveiling, which initially happened back in 2018, would take place on April Fool’s Day. Initial deliveries at the 2018 event were slotted for 2020, but delays in the project, as well as prioritization of other things, continued to push the Roadster back.
The Tesla Roadster is perhaps the most anticipated vehicle in the company’s history, but those who have been waiting anxiously for it will have to push their timelines back once again.
Tesla CEO Elon Musk has revealed that the company is once again pushing back the unveiling event that was originally planned for April 1. It will now take place “probably in late April.”
True.
New Roadster unveil probably in late April. https://t.co/NShZxpK5cI
— Elon Musk (@elonmusk) March 17, 2026
Musk announced last year that the unveiling, which initially happened back in 2018, would take place on April Fool’s Day. Initial deliveries at the 2018 event were slotted for 2020, but delays in the project, as well as prioritization of other things, continued to push the Roadster back.
There has been so much hype about the Roadster that people are right to be excited about the prospect of its existence.
Musk’s most recent rumblings about the vehicle came last Fall, when he appeared on the Joe Rogan Experience podcast, where he once again hinted the car would be able to hover for a short period.
He said:
“Whether it’s good or bad, it will be unforgettable. My friend Peter Thiel once reflected that the future was supposed to have flying cars, but we don’t have flying cars. I think if Peter wants a flying car, he should be able to buy one…I think it has a shot at being the most memorable product unveiling ever. [It will be unveiled] hopefully before the end of the year. You know, we need to make sure that it works. This is some crazy technology in this car. Let’s just put it this way: if you took all the James Bond cars and combined them, it’s crazier than that.”
Additionally, he said the vehicle would not be something that would prioritize safety. Musk said that “If safety is your number one goal, do not buy the Roadster.” It’s made for speed and excitement, not for grocery-getting.
Elon Musk just said some crazy stuff about the Tesla Roadster
As the April 1 unveiling event that was originally planned was nearing without any communication to fans, media, or anyone who would potentially be in attendance, it seemed to be pretty obvious that Tesla was not ready to pull the trigger on the event quite yet.
There could be some last-minute things to finalize, or it could be something else. One thing is for certain, though: we are not super surprised that things were moved back.
Tesla has definitely been putting some things in motion for the Roadster. A few months back, Tesla started to ramp up hiring for the Roadster, and earlier in March, it submitted a patent application for a new seat design.
Elon Musk
Tesla named by U.S. Gov. in $4.3B battery deal for American-made cells
What began as an open secret in the energy industry was confirmed by the U.S. Department of the Interior on Monday: Tesla is the buyer behind LG Energy Solution’s blockbuster $4.3 billion battery supply agreement.
What began as an open secret in the energy industry is becoming more real after the U.S. Department of the Interior named Tesla as the stakeholder in the LG Energy Solution’s blockbuster $4.3 billion battery supply agreement.
Tesla and LG Energy Solution are expanding their partnership to build a LFP prismatic battery cell manufacturing facility in Lansing, Michigan, launching production in 2027. The announcement, made as part of the Indo-Pacific Energy Security Summit results, ends months of speculation.
“American-made cells will power Tesla’s Megapack 3 energy storage systems produced in Houston, creating a robust domestic battery supply chain.”, notes a press release on the U.S. Department of the Interior website.
Tesla has long utilized China’s Contemporary Amperex Technology Co. (CATL), the world’s largest LFP battery maker, as one of its primary suppliers. That relationship made financial sense for years, considering that Chinese LFP cells were cheap, abundant, and reliable. But with escalated tariffs on Chinese imports and an increasingly growing Tesla Energy business that’s particularly reliant on LFP cells for products including its Megapack battery storage units designed for utilities and large-scale commercial projects.
The announcement of a deepened partnership between LG Energy Solution and Tesla has strategic logic for both parties. For Tesla, it secures a tariff-compliant, domestically produced battery supply for its fast-growing energy division. LGES, now producing LFP batteries in Michigan, becomes the only major supplier currently scaling U.S. production, outpacing rivals like Samsung SDI and SK On. LG Energy Solution’s Lansing plant, formerly known as Ultium Cells 3, was previously operated as a joint venture with General Motors. LGES acquired GM’s stake in May 2025 and now fully owns the site, with a production capacity of 50 GWh per year. LG Energy said the contract includes options to extend the supply period by up to seven years and boost volumes based on further consultations.
For the broader industry, the ripple effects are significant. This deal signals that domestic battery manufacturing can be financially viable and not just aspirational. Utilities, energy developers, and rival automakers will take note as American-made LFP supply becomes a competitive reality rather than a distant promise.
For consumers, the benefits will take time but are real. A more resilient, U.S.-based supply chain means fewer price shocks from trade disputes, more stable Megapack availability for the grid storage projects that reduce electricity costs, and long-term downward pressure on energy storage prices as domestic production scales.
Deliveries are set to begin in 2027 and run through mid-2030, and as grid storage demand accelerates, reliable, US-made battery supply is no longer a future ambition. It is becoming a core requirement of the country’s energy strategy.
Tesla Robotaxi appears to be heading to a new U.S. city
Tesla Roadster gets new unveiling date once again
