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Ex-SpaceX engine expert to help design rockets built for launch on world’s largest jet

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8 years ago

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Stratolaunch, an aerospace company funded by Microsoft-made billionaire Paul Allen to build the world’s largest flightworthy aircraft, has announced a decision to build its own liquid-fueled rockets, to be air-launched from the aforementioned mega-plane.

Targeting an inaugural launch of the first version of the rocket – currently nicknamed “Kraken” – as early as 2022, Stratolaunch has chosen Jeff Thornburg, formerly SpaceX’s Vice President of Propulsion Engineering and the father of the company’s Mars-focused Raptor engine, to lead its foray into in-house rocket propulsion development and manufacturing.

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But first: building the world’s largest aircraft

Stratolaunch’s first task at hand, however, is to begin flight-testing the largest (hopefully) operational aircraft in history, a prerequisite for the company’s longer-term orbital rocket and spaceplane aspirations. Nicknamed “Roc” after a mythical (and fictional) bird so large it could carry an elephant, the plane certainly lives up to its namesake. Featuring a full six of the same engines that power Boeing’s once-record-breaking 747 airliner and a wingspan that could easily fit three smaller 737 airliners with room to spare, it is genuinely difficult (if not impossible) to successfully convey the sheer scale of Roc outside of witnessing it in person.

Stationed in California’s Mojave Desert, the aircraft’s one and only copy is, for the most part, completed and has spent the brunt of 2018 conducting runway taxi tests, hopefully culminating in an inaugural flight test later this year or early next year. Designed to lift orbital-class rockets weighing as much as 250 metric tons (550,000 lb) to an altitude of at least 9100 meters (30,000 feet), the primary benefit of using aircraft as launch platforms derives from the simple fact that the atmospheric density at 30,000 feet is more than three times less than that at sea level. Similar to aircraft, rocket performance dramatically improves as atmospheric density decreases: less atmosphere means lower drag and pressure.

Rockets that launch from sea-level have to grapple with the difficulties of Earth’s relatively thick atmosphere at that height, with major launch events like “Max-Q” being big concerns almost solely because the dense air exerts major forces on launch vehicles and demands extreme measures like throttling down booster engines (very inefficient) and optimizing structures for aerodynamic efficiency despite the fact that rockets spend very little time operating in a significant atmosphere.

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A launch pad without a rocket (sort of)

However, the simple fact of the matter is that billionaire Paul Allen’s colossal aircraft essentially does not have a single air-launched rocket in the world that can properly take advantage of its capabilities. Originally sized and designed with an air-launched version of SpaceX’s Falcon 9 in mind, that relationship folded amicably after roughly a year (2012), at which point SpaceX realized it would need to almost completely redesign a unique variant of Falcon 9. Your author will readily admit that they have admired the insanity of such a massive plane while still severely doubting its practical utility.

Thankfully, it appears that Allen is adamantly opposed to the idea that Stratolaunch is some silly whim to build the world’s largest plane. Rather, he is exceptionally reserved and pragmatic when discussing the aerial launch platform, according to a recent and extensive interview by Wired Magazine’s Steven Levy.

“Allen isn’t one to show exuberance, and when he speaks about the plane he focuses on its future utility. ‘When you see that giant plane, it’s a little nutty,’ he says. ‘And you don’t build it unless you’re very serious, not only about wanting to see the plane fly but to see it fulfill its purpose. Which is getting vehicles in orbit.’ – Paul Allen, 2018

 

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Currently, Orbital ATK’s (now Northrop Grumman Innovation Systems) air-launched Pegasus XL rocket is the only “customer” in the world that can realistically use Stratolaunch as a launch platform, not exactly an impressive or sustainable launch vehicle with a maximum performance of less than 450 kg (~1000 lbs) to low Earth orbit for an incredible ~$40 million per (expendable) flight.

To answer that call and ensure Stratolaunch’s utility, the company reportedly began seriously considering its own in-house expendable and reusable rockets and propulsion systems sometime in 2016, plans that have since grown concrete and been publicly embedded into Stratolaunch’s overarching mission. Nicknamed “Kraken” after the mythical sea monster, the company hopes to develop an initially expendable rocket system capable of launching 3400 – 6000 kg (~7500 – 13250 lbs) into low Earth orbit with single booster and triple booster variants. Further down the line, Stratolaunch is eyeing the design and production of a fully and rapidly reusable orbital spaceplane, potentially including a version that would carry astronauts into space.

 

Normally, one might simply roll their eyes at yet another startup touting small(ish) expendable rockets with first launches no earlier than the early 2020s – the market is getting to be absurdly and impossibly overcrowded at this point. However, Stratolaunch differs for one fundamental and reason: they have placed ex-SpaceX propulsion executive and expert Jeff Thornburg at the helm of the company’s freshly public rocket propulsion wing. While at SpaceX, Mr. Thornburg spent all but one of his five years with the company (2011-2015) single-mindedly focused on the development and engineering of all aspects of the Raptor rocket engine, a next-generation propulsion system designed to enable SpaceX’s sustainable colonization of Mars.

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Raptor is an exceptional rocket engine thanks in no small part to Thornburg’s brilliance as a propulsion engineer, and that same brilliance and half-decade of experience at the most successful rocket startup in existence could ultimately prove a massive boon for Stratolaunch’s otherwise interesting but unexceptional expendable rocket concepts.

Put simply, under Jeff Thornburg’s direction and with access to founder Paul Allen’s considerable wealth, Stratolaunch is undoubtedly worth keeping a close eye in the future, both far and near.

For prompt updates, on-the-ground perspectives, and unique glimpses of SpaceX’s rocket recovery fleet check out our brand new LaunchPad and LandingZone newsletters!

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Eric Ralph is Teslarati's senior spaceflight reporter and has been covering the industry in some capacity for almost half a decade, largely spurred in 2016 by a trip to Mexico to watch Elon Musk reveal SpaceX's plans for Mars in person. Aside from spreading interest and excitement about spaceflight far and wide, his primary goal is to cover humanity's ongoing efforts to expand beyond Earth to the Moon, Mars, and elsewhere.

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Tesla’s Semi truck factory is open with a detail that changes everything

Tesla’s dedicated Nevada Semi factory has opened, targeting 50,000 trucks per year as fleet adoptions accelerate nationwide.

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2 hours ago

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April 10, 2026

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Nearly nine years after Elon Musk unveiled the Tesla Semi in November 2017, the company is now opening a dedicated factory just outside of Reno, Nevada, and ramping toward mass production of 50,000 trucks per year.

Volume production began in March 2026 at the new Tesla Semi factory, with the competitive advantage not being the factory itself. Rather, it’s where Tesla built it. By constructing the 1.7 million square foot facility directly adjacent to Gigafactory Nevada in Sparks, Tesla closed the one supply chain loop that had delayed the Semi program for years. The 4680 battery cells that power the Semi are manufactured in the same complex, which significantly streamlines supply logistics. That single decision eliminates the bottleneck that forced Tesla to prioritize battery supply for passenger cars over the Semi throughout 2020, 2021, and 2022, which is precisely why the first deliveries slipped three years past the original target. Every other electric truck manufacturer sources its battery cells from a separate supplier, ships them to a separate factory, and absorbs the cost and delay that comes with that. Tesla built its Semi factory around its battery factory, and that vertical integration is what makes 50,000 trucks per year a realistic number rather than an aspirational one.

At the 2025 Annual Shareholder Meeting, Musk was direct about where things stood, stating “Starting next year, we will manufacture the Tesla Semi. We already have a lot of prototype Semis in operation – PepsiCo and other companies have been using them for some time. But in 2026, we’ll begin volume production at our Northern Nevada factory.” Full ramp to volume output is targeted before June 30, 2026.


The first limited deliveries happened in December 2022 to PepsiCo, which eventually doubled its fleet to 50 trucks out of its California distribution facility. Since then the Semi has been showing up in more corporate fleets. As Teslarati noted in March, a Ralph’s Supermarkets branded Semi was spotted on a Los Angeles highway, confirming Kroger’s partnership with Tesla to deploy up to 500 electric Semis. Walmart, Costco, Sysco, US Foods, DHL, Hight Logistics and WattEV are among the companies actively running or receiving units. DHL logged real-world efficiency of 1.72 kWh per mile under a full 75,000 pound load over 388 miles, matching Tesla’s targets closely.

The 2026 production model arrives with meaningful upgrades over the original, with a 1,000 pound weight reduction, updated aerodynamics, and support for 1.2 MW Megacharger speeds that can restore 60% of range in around 30 minutes during a mandatory driver rest break. Tesla opened its first public Megacharger in Ontario, California in March, positioned near the I-10 and I-15 interchange serving the Ports of Los Angeles and Long Beach. The company plans 37 Megacharger sites by end of 2026 and 66 total across 15 states by early 2027, with construction beginning at the nation’s largest truck stop operator in the first half of this year.

Tesla reveals various improvements to the Semi in new piece with Jay Leno

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Musk has described the Semi’s economics as a straightforward case. “The Semi is a TCO no-brainer,” he said, noting the total cost of ownership is “much, much cheaper than any other transportation you could have.” At under $300,000, the truck costs roughly double a comparable diesel, but California’s $200,000 per vehicle subsidy has driven over 1,000 state orders alone. As Teslarati has tracked, the prototype fleet accumulated over 13.5 million miles with 95% fleet uptime before production ever scaled. The factory opening now turns that proof of concept into a production program.

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Tesla Full Self-Driving gets first-ever European approval

Tesla owners in the Netherlands with a Full Self-Driving subscription will receive a software update “shortly,” the company said, activating the operation of the company’s semi-autonomous driving tech for the first time in Europe.

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5 hours ago

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April 10, 2026

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Credit: Tesla AI | X

Tesla Full Self-Driving (Supervised) got its first-ever European approval, as the Netherlands gave the suite the green light to begin operation.

Tesla owners in the Netherlands with a Full Self-Driving subscription will receive a software update “shortly,” the company said, activating the operation of the company’s semi-autonomous driving tech for the first time in Europe.

The Dutch vehicle authority RDW granted the type approval after more than 18 months of rigorous testing on both closed tracks and public roads. FSD Supervised complies with UN R-171 standards and benefits from Article 39 exemptions under EU Regulation 2018/858. Importantly, it is not a fully autonomous vehicle.

The RDW stressed that the driver remains fully responsible and must maintain attention at all times. “Safety is paramount for the RDW,” the authority stated. “Proper use of this driver assistance system contributes positively to road safety.” Sensors monitor driver alertness, issuing warnings if eyes leave the road or hands are unavailable to take control immediately.

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CEO Elon Musk also commented on the approval in a post on X, saying:

“First (supervised) FSD approval in Europe! Congratulations to the Tesla team and thank you to the regulatory authorities in the Netherlands for all of the hard work required to make this happen.”

Trained on billions of kilometers of real-world driving data, FSD Supervised allows the vehicle to handle residential streets, dense city traffic, and highways under constant supervision. Tesla’s post declared:

“It can drive you almost anywhere under your supervision – from residential roads to city streets & highways. No other vehicle can do this.”

The company added that it is “excited to bring FSD Supervised to more European countries soon.”

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This national approval paves the way for broader EU adoption. Other member states can recognize the Dutch certification individually, with a potential bloc-wide rollout via European Commission committee vote anticipated by this Summer. The decision underscores Europe’s stricter safety and documentation requirements compared to U.S. self-certification.

Tesla Europe shares FSD test video weeks ahead of launch target

The Netherlands’ approval represents a pivotal step for Tesla in Europe, where complex regulations and mixed traffic have delayed rollout. Musk added that the RDW was “rigorous” in its assessment of FSD.

By proving the system’s safety in one of the continent’s most bicycle- and tram-heavy nations, Tesla positions itself to transform mobility across the EU—delivering greater convenience while keeping drivers firmly in control.

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As the first domino falls, anticipation builds for FSD Supervised to reach additional countries soon.

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Tesla is using a redesigned Cybertruck battery cell to mitigate Semi challenges

It is perhaps the most recent example of Tesla using unique engineering prowess and cross-pollinating vehicle elements to solve common problems, something it does better than most companies out there.

Published

14 hours ago

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April 10, 2026

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Credit: Tesla

Tesla revealed that it is utilizing redesigned Cybertruck battery cells in its Long Range Semi to mitigate some pertinent challenges that come with long-haul logistics.

It is perhaps the most recent example of Tesla using unique engineering prowess and cross-pollinating vehicle elements to solve common problems, something it does better than most companies out there.

Tesla’s long-awaited Semi truck is entering production at its Nevada Gigafactory, and fresh factory footage reveals a clever evolution in its battery technology.

The Long Range variant, designed for up to 500 miles of real-world range, relies on a structural battery pack that uses the same 4680-form-factor cells found in the Cybertruck.

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However, Tesla engineers have completely redesigned the pack’s architecture—shifting from the flat, pancake-style modules typical in passenger vehicles to a compact, vertical cubic layout. This change isn’t just about cramming more energy into the chassis; it’s a targeted solution to one of electric trucking’s biggest headaches: range loss in cold climates.

Dan Priestley, Head of the Tesla Semi program, said:

“We’re using essentially the same cell out of Cybertruck, but our cars packs are more like a pancake. Whereas these are more like a cube. You get a lot of energy stored in a small space. You can only do this if you design the vehicle to be electric from the ground up.”

In conventional EVs, battery packs are laid out horizontally in wide, flat arrays to fit under the floor. While this works for cars and even the Cybertruck’s structural pack, it exposes a large surface area to the elements.

Heat escapes quickly, especially overnight when the truck is parked. Cold temperatures slow chemical reactions inside lithium-ion cells, reducing available energy and forcing the vehicle to expend extra power warming the battery and cabin.

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Real-world tests on vehicles like the Cybertruck show winter range losses of 20-40 percent, depending on conditions. For long-haul truck drivers operating in Canada, Scandinavia, or the northern U.S., this “silent killer” means unplanned stops, reduced payloads, and higher operating costs.

From personal experience, cold weather still impacts EV batteries even with various inventions and strategies that companies have come up with. In the cold Pennsylvania winter, charging was much more frequent for me due to range loss due to temperatures.

Tesla’s cubic battery pack flips the script. By arranging the 4680 cells in tall, dense vertical stacks, the pack minimizes external surface area relative to its volume—essentially turning the battery into its own thermal blanket.

Factory video from the Semi assembly line shows these large, yellow-green structural modules mounted directly onto the chassis, forming a near-cube shape.

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The reduced exposure helps the pack retain heat generated during operation, keeping cells closer to their optimal temperature even after hours in sub-zero conditions.

The design doesn’t stop there. Tesla pairs the cubic pack with an advanced heat pump system that actively recycles thermal energy from the motors, brakes, and even ambient air.

Tesla reveals various improvements to the Semi in new piece with Jay Leno

Unlike passive systems in earlier EVs, this architecture transfers waste heat back into the battery, maintaining readiness for morning departures without draining the pack.

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Executives have noted that the combination, cubic geometry plus intelligent thermal management, dramatically cuts overnight cooldown and range degradation, making the Semi viable for 24/7 fleet operations in harsh winters.

Beyond cold-weather performance, the redesigned pack integrates structurally with the truck’s frame, enhancing rigidity while simplifying assembly. Production footage shows workers installing the massive modules early in the line, signaling that the Semi’s battery is now a core chassis component rather than an add-on.

Using proven 4680 cells keeps costs down and leverages Tesla’s scaled manufacturing know-how from Cybertruck and Model Y lines.

Tesla’s focus on ramping up Semi output will lean on small innovative steps like this one. Truckers are not immune to traveling in cold weather conditions, and changes like this one will help make them more effective while also increasing output by logistics operators who choose to go all-electric with the Tesla Semi.

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