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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Lifestyle
Tesla Semi hauls fresh Cybercab batch as Robotaxi era takes hold
A Tesla Semi was filmed hauling Cybercab units out of Giga Texas for the first time.
A Tesla Semi loaded with Cybercab units was recently filmed leaving Gigafactory Texas, marking what appears to be the first documented delivery run of Tesla’s autonomous two-seater. The footage shows multiple Cybercabs secured on a flatbed trailer being hauled by a production Tesla Semi, a truck rated for a gross combination weight of 82,000 lbs. The location is consistent with Giga Texas in Austin, where Cybercab production has been ramping since February 2026.
The sighting follows a wave of Cybercab activity at the Austin facility. In late April, drone operator Joe Tegtmeyer spotted approximately 60 Cybercabs parked in two organized groups in the factory’s outbound lot, the largest concentration observed to date. Units being staged in an outbound lot is a standard pre-delivery step, and the Semi footage is the logical next frame in that sequence.
En route with @tesla_semi pic.twitter.com/ZfuOjaeLH1
— Tesla Robotaxi (@robotaxi) May 7, 2026
This is not the first time Tesla has used its own Semi to move Tesla products. When the Semi was unveiled in 2017, Musk noted it would be used for Tesla’s own operations, and over the years Semi prototypes were spotted carrying cargo ranging from concrete weights to Tesla vehicles being delivered to consumers. In 2023, a Semi was photographed transporting a Cybertruck on a trailer ahead of that vehicle’s delivery launch.
The Cybercab itself was first revealed publicly at Tesla’s “We, Robot” event on October 10, 2024, at Warner Bros. Studios in Burbank, where 20 pre-production units gave attendees rides around the studio lot. Musk stated at the event that Tesla intends to produce the Cybercab before 2027. The first production unit rolled off the Giga Texas line on February 17, 2026, with Musk posting on X: “Congratulations to the Tesla team on making the first production Cybercab.”
Tesla’s annual production goal is 2 million Cybercabs per year once multiple factories reach full design capacity, with the company targeting a price under $30,000 per unit. Tesla has confirmed plans to expand its robotaxi service to seven cities in the first half of 2026, including Dallas, Houston, Phoenix, Miami, Orlando, Tampa, and Las Vegas, building on the unsupervised service already running in Austin. Musk has said he expects robotaxis to cover between a quarter and half of the United States by end of year.
Cybertruck
Tesla Cybertruck too safe for even Musk’s biggest critics to ignore
Krassenstein’s decision reveals that superior safety isn’t a partisan issue. For parents prioritizing family protection over personal or political grudges, the Cybertruck has become too safe to ignore.
The Tesla Cybertruck is an extremely polarizing vehicle because of its potential symbolism as a political stance instead of just a pickup truck — or at least that is what many would want you to believe.
Of course, the Cybertruck is an icon of Tesla culture, and it is one of those things that never has a middle ground: you love it, or you don’t.
But maybe there is an establishment of that “grey area” happening.
In a striking illustration of engineering triumph over political tribalism, prominent Elon Musk critic Brian Krassenstein has purchased a Tesla Cybertruck, openly citing its exceptional safety as the deciding factor for his family.
The announcement on X triggered predictable backlash, yet it underscores a growing reality: the Cybertruck’s safety credentials are proving impossible for even Musk’s fiercest detractors to dismiss.
I might get hate for this too but I bought a Cybertruck.
With a young family, safety was important and so is not polluting the atmosphere with $5 a gallon gasoline. pic.twitter.com/XJqFqR6O9r
— Brian Krassenstein (@krassenstein) May 6, 2026
Krassenstein, who has repeatedly clashed with Musk over issues ranging from content moderation and “wokeness” to public health figures, made no attempt to hide his reservations. In his May 6 post, he acknowledged the coming criticism: “I might get hate for this too but I bought a Cybertruck.”
He stressed that the decision had “nothing to do with Elon or politics,” pointing instead to practical advantages—his existing Tesla charger, eligibility for Full Self-Driving upgrades, a returning-owner discount, and crucially, the vehicle’s strong safety profile.
With gasoline prices hovering near $5 a gallon in some areas, he also highlighted the environmental benefit of switching from a polluting combustion engine.
The numbers, data, and awards validate Krassenstein’s choice.
The 2025 Cybertruck earned the Insurance Institute for Highway Safety’s (IIHS) elite Top Safety Pick+ award—the only pickup truck to achieve this highest rating. It delivered “Good” scores across every crashworthiness category, including the challenging updated moderate overlap front crash test, while excelling in crash avoidance and mitigation systems.
The National Highway Traffic Safety Administration (NHTSA) awarded it a perfect 5-star overall rating, with top marks in frontal, side, and rollover categories. No other pickup truck holds both distinctions simultaneously.
Tesla Cybertruck crash test rating situation revealed by NHTSA, IIHS
Beyond lab results, the Cybertruck’s stainless-steel exoskeleton and ultra-rigid structure have demonstrated remarkable real-world resilience. Owners have reported surviving high-speed collisions with minimal cabin intrusion.
In one widely discussed incident, a Cybertruck endured a 70 mph sideswipe on the interstate; the driver reported barely feeling the impact while the other vehicle was heavily damaged.
Tesla’s crash demonstrations and independent analyses consistently show how the vehicle’s design prioritizes occupant protection through a fortified passenger cell rather than traditional crumple zones, giving families superior safeguarding in many common crash scenarios.
The online pile-on following Krassenstein’s post focused on aesthetics, politics, and perceived hypocrisy rather than the data. Critics called the angular truck “ugly” or accused him of selling out.
Yet his purchase highlights an inconvenient truth for polarized discourse: when objective safety metrics—IIHS awards, NHTSA ratings, and documented crash performance—point decisively toward one vehicle, even Musk’s biggest critics are forced to confront its merits.
Krassenstein’s decision reveals that superior safety isn’t a partisan issue. For parents prioritizing family protection over personal or political grudges, the Cybertruck has become too safe to ignore.
SpaceXAI announced today that it had signed an agreement with Anthropic to give the company access to its Colossus 1 data center in Memphis, Tennessee.
It is a monumental deal as Anthropic will gain access to all of the compute at the plant, delivering more than 300 megawatts of power and over 220,000 NVIDIA GPUs within the month.
Anthropic’s Claude AI account on X announced the partnership:
“We’ve agreed to a partnership with SpaceX that will substantially increase our compute capacity. This, along with our other recent compute deals, means that we’ve been able to increase our usage limits for Claude Code and the Claude API.”
The company is also:
- Doubling Claude Code’s 5-hour rate limits for Pro, Max, and Team plans;
- Removing the peak hours limit reduction on Claude Code for Pro and Max plans; and
- Substantially raising its API rate limits for Opus models.
We’ve agreed to a partnership with @SpaceX that will substantially increase our compute capacity.
This, along with our other recent compute deals, means that we’ve been able to increase our usage limits for Claude Code and the Claude API.
— Claude (@claudeai) May 6, 2026
SpaceX also published its own release on the new agreement, noting that it is “the only organization with the launch cadence, mass-to-orbit economics, and constellation operations experience to make orbital compute a near-term engineering program rather than a research concept.”
CEO Elon Musk also commented on the partnership and shed light on intense meetings he had with senior members of Anthropic last week, stating, “nobody set on my evil detector.”
Same here.
By way of background for those who care, I spent a lot of time last week with senior members of the Anthropic team to understand what they do to ensure Claude is good for humanity and was impressed.
Everyone I met was highly competent and cared a great deal about…
— Elon Musk (@elonmusk) May 6, 2026
This has turned the argument that SpaceX is as much an AI company as a space exploration company into a very valid argument:
SpaceX is following in Tesla’s footsteps in a way nobody expected
Nevertheless, this is an incredibly valuable and important move in the grand scheme of things. AI scaling is fundamentally bottlenecked by compute, and demand for Claude has surged, bringing terrestrial power grids, land, and cooling operations hitting limits everywhere.
Anthropic has been aggressively signing multiple large-scale deals to be competitive in the space, including:
- Up to 5GW with Amazon
- 5GW with Google and Broadcom
- Strategic $30b Azure deal with Microsoft/NVIDIA
- $50b U.S. infrastructure investment with Fluidstack
Access to Colossus 1 gives Anthropic immediate relief on NVIDIA GPU capacity. For SpaceXAI, it turns its rapid buildout into revenue. It also showcases its ability to deliver at world-leading speed and scale.
Most importantly, it plants the seed that its much larger vision, orbital AI compute, is totally viable.
Starlink V3 satellites could enable SpaceX’s orbital computing plans: Musk
Within the month, Anthropic will begin using 100 percent of Colossus 1’s compute, directly expanding capacity for Claude Pro and Max subscribers and the API. This means fewer limits, faster responses, and support for heavier workloads.
In the long term, meaning 2026 and beyond, there will be a continued rollout of other multi-GW deals Anthropic has signed, and an early exploration of orbital compute with SpaceXAI.
Tesla Semi hauls fresh Cybercab batch as Robotaxi era takes hold
Tesla Cybertruck too safe for even Musk’s biggest critics to ignore
