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.
- 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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Elon Musk
The Boring Company clears final Nashville hurdle: Music City loop is full speed ahead
The Boring Company has cleared its final Nashville hurdles, putting the Music City Loop on track for 2026.
The Boring Company has cleared one of its most significant regulatory milestones yet, securing a key easement from the Music City Center in Nashville just days ago, the latest in a series of approvals that have pushed the Music City Loop project firmly into construction reality.
On March 24, 2026, the Convention Center Authority voted to grant The Boring Company access to an easement along the west side of the Music City Center property, allowing tunneling beneath the privately owned venue. The move follows a unanimous 7-0 vote by the Metro Nashville Airport Authority on February 18, and a joint state and federal approval from the Tennessee Department of Transportation and the Federal Highway Administration on February 25. Together, these green lights have cleared the path for a roughly 10-mile underground tunnel connecting downtown Nashville to Nashville International Airport, with potential extensions into midtown along West End Avenue.
Music City Loop could highlight The Boring Company’s real disruption
Nashville was selected by The Boring Company largely because of its rapid population growth and the strain that growth has placed on surface infrastructure. Traffic has become a persistent problem for residents, convention visitors, and airport travelers alike. The Music City Loop promises an approximately 8-minute underground transit time between downtown and the Nashville International Airport (BNA), removing thousands of vehicles from surface roads daily while operating as a fully electric, zero-emissions system at no cost to taxpayers.
The project fits squarely within a broader vision Musk has championed for years. In responding to a breakdown of the Loop’s construction costs, Musk posted on X: “Tunnels are so underrated.” The comment reflected a longstanding belief that underground transit represents one of the most cost-effective and scalable infrastructure solutions available. The Boring Company has claimed it can build 13 miles of twin tunnels in Nashville for between $240 million and $300 million total, a fraction of what comparable projects cost elsewhere in the country.

Image Credit: The Boring Company/Twitter
The Las Vegas Loop, The Boring Company’s first operational system, has served as a proof of concept. During the CONEXPO trade show in March 2026, the Vegas Loop transported approximately 82,000 passengers over five days at the Las Vegas Convention Center, demonstrating the system’s capacity during large-scale events. Nashville draws millions of convention visitors and tourists each year, and local business leaders have pointed to that same capacity as a major draw for supporting the project.
The Music City Loop was first announced in July 2025. Construction began within hours of the February 25 state approval, with The Boring Company’s Prufrock tunneling machine already in the ground the same evening. The first operational segment is targeted for late 2026, with the full route expected to be complete by 2029. The project represents one of the largest privately funded infrastructure efforts currently underway in the United States.
Elon Musk
Elon Musk demands Delaware Judge recuse herself after ‘support’ post celebrating $2B court loss
A banner on the post read “Katie McCormick supports this,” using LinkedIn’s heart-in-hand “support” icon, an endorsement stronger than a simple “like.” Musk’s lawyers argue the action creates “a perception of bias against Mr. Musk,” warranting immediate recusal to preserve judicial impartiality.
Tesla CEO Elon Musk’s legal team has filed a motion demanding that Delaware Chancellor Kathaleen McCormick disqualify herself from an ongoing high-stakes Tesla shareholder lawsuit.
The filing, submitted March 25, cites an apparent LinkedIn “support” reaction from McCormick’s account to a post celebrating a $2 billion jury verdict against Musk in a separate California securities-fraud case.
The move escalates long-simmering tensions between Musk, Tesla, and the Delaware judiciary, where McCormick previously presided over the landmark challenge to Musk’s record $56 billion 2018 compensation package.
Delaware Supreme Court reinstates Elon Musk’s 2018 Tesla CEO pay package
The LinkedIn post was written by Harry Plotkin, a Southern California jury consultant who assisted the plaintiffs who sued Musk over 2022 tweets about his Twitter acquisition. Plotkin praised the trial team for “standing up for the little guy against the richest man in the world.”
The New York Post initially reported the story.
A banner on the post read “Katie McCormick supports this,” using LinkedIn’s heart-in-hand “support” icon, an endorsement stronger than a simple “like.” Musk’s lawyers argue the action creates “a perception of bias against Mr. Musk,” warranting immediate recusal to preserve judicial impartiality.
This appears to be unequivocal proof she denied the pay package because of her own personal beliefs and not the law.
Corruption. https://t.co/8dvgcfYuvh
— TESLARATI (@Teslarati) March 25, 2026
McCormick swiftly denied intentional endorsement. In a letter to attorneys, she stated she was unaware of the interaction until LinkedIn notified her. She wrote:
“I either did not click the ‘support’ icon at all, or I did so accidentally. I do not believe that I did it accidentally.”
The chancellor maintains the reaction was inadvertent, but critics, including Musk allies, call the explanation implausible given the platform’s deliberate interface.
McCormick’s central role in the Tesla pay-package litigation underscores the stakes. In Tornetta v. Musk, in January 2024, she ruled the 2018 performance-based stock-option grant, potentially worth $56 billion at the time and now valued far higher, was invalid.
The package consisted of 12 tranches of options, each vesting only after Tesla achieved ambitious market-cap and operational milestones. McCormick found Musk exercised “transaction-specific control” over Tesla as a controlling stockholder, the board lacked sufficient independence, and proxy disclosures to shareholders were materially deficient.
Applying the entire-fairness standard, she concluded defendants failed to prove the deal was fair in process or price and ordered full rescission, an “unfathomable” remedy she described as necessary to deter fiduciary breaches.
After the ruling, Tesla shareholders ratified the package a second time in June 2024. McCormick rejected that ratification in December 2024, holding that post-trial votes could not cure defects.
Tesla appealed. On December 19 of last year, the Delaware Supreme Court unanimously reversed the rescission remedy while largely leaving McCormick’s liability findings intact. The high court deemed total unwinding inequitable and impractical, restoring the package but awarding the plaintiff only nominal $1 damages plus reduced attorneys’ fees. Musk ultimately received the full award.
The current recusal motion arises in yet another Tesla derivative suit before McCormick. Legal observers say granting it could signal heightened scrutiny of judicial social-media activity; denial might reinforce perceptions of an insular Delaware bench.
Broader fallout includes accelerated corporate migration out of Delaware, Musk himself moved Tesla’s incorporation to Texas after the first ruling, and renewed debate over whether the state’s specialized courts remain the gold standard for corporate governance disputes.
A decision is expected soon; whichever way it lands, the episode highlights the fragile balance between judicial independence and public confidence in high-profile litigation.
News
Tesla Cybercab spotted next to Model Y shows size comparison
The Model Y is Tesla’s most-popular vehicle and has been atop the world’s best-selling rankings for the last three years. The Cybercab, while yet to be released, could potentially surpass the Model Y due to its planned accessible price, potential for passive income for owners, and focus on autonomy.
The Tesla Cybercab and Tesla Model Y are perhaps two of the company’s most-discussed vehicles, and although they are geared toward different things, a recent image of the two shows a side-by-side size comparison and how they stack up dimensionally.
The Model Y is Tesla’s most-popular vehicle and has been atop the world’s best-selling rankings for the last three years. The Cybercab, while yet to be released, could potentially surpass the Model Y due to its planned accessible price, potential for passive income for owners, and focus on autonomy.
Geared as a ride-sharing vehicle, it only has two seats. However, the car will be responsible for hauling two people around to various destinations completely autonomously. How they differ in terms of size is striking.
In a new aerial image shared by drone operator and Gigafactory Texas observer Joe Tegtmeyer, the two vehicles were seen side by side, offering perhaps the first clear look at how they differ in size.
Tesla Model Y vs. Tesla Cybercab:
✅ Overall Length:⁰Model Y: 188.7 inches (4,794 mm)⁰Cybercab: ~175 inches (≈4,445 mm)⁰→ Cybercab is about 13–14 inches shorter (roughly the length of a large suitcase).
✅ Overall Width (excluding mirrors):⁰Model Y: 75.6 inches (1,920 mm)… https://t.co/PsVwzhw1pe pic.twitter.com/58JQ5ssQIO
— TESLARATI (@Teslarati) March 25, 2026
Dimensionally, the differences are striking. The Model Y stretches roughly 188 inches long, 75.6 inches wide, excluding its mirrors, and stands 64 inches tall on a 113.8-inch wheelbase. The Cybercab measures approximately 175 inches in length, about a foot shorter, and just 63 inches wide.
That narrower stance gives the Cybercab a dramatically more compact silhouette, making it easier to maneuver in tight urban environments and park in standard spaces that would feel cramped for the Model Y. Height is also lower on the Cybercab, contributing to its sleek, coupe-like profile versus the Model Y’s taller crossover shape.
Visually, the contrast is unmistakable. The Model Y presents as a family-friendly SUV with conventional doors, a prominent hood, and a spacious glass roof.
The Cybercab eliminates the steering wheel and pedals entirely, creating a clean, futuristic cabin that feels more lounge than cockpit.
Its doors open in a distinctive, wide-swinging motion, and the body features smoother, more aerodynamic lines optimized for autonomy. Parked beside a Model Y, the Cybercab appears almost toy-like in width and length, yet its low-slung stance and minimalist design emphasize agility over bulk.
🚨 We caught up with the Tesla Cybercab today in The Bay Area: pic.twitter.com/9awXiK26ue
— TESLARATI (@Teslarati) March 24, 2026
Cargo capacity tells another part of the story. The Model Y offers generous real-world utility: 4.1 cubic feet in the front trunk and 30.2 cubic feet behind the rear seats, expanding to 72 cubic feet with the second row folded flat.
It comfortably swallows groceries, luggage, or sports equipment for five passengers. The Cybercab, designed for two riders, trades that volume for targeted efficiency.
It features a rear hatch with enough space for two carry-on suitcases and personal items, plenty for the typical robotaxi trip, while maintaining impressive legroom and headroom for its occupants.
In short, the Model Y prioritizes versatility and family hauling with its larger footprint and abundant storage. The Cybercab sacrifices size for simplicity, cost, and urban nimbleness.
At roughly 12 inches shorter and 12 inches narrower, it embodies Tesla’s vision for scalable, affordable autonomy: smaller on the outside, smarter inside, and ready to redefine how we move through cities.
The Cybercab and Model Y both will contribute to Tesla’s fully autonomous future. However, the size comparison gives a good look into how the vehicles are the same, and how they differ, and what riders should anticipate as the Cybercab enters production in the coming weeks.








