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Ex-SpaceX engine expert to help design rockets built for launch on world’s largest jet
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.
Stratolaunch has confirmed what most people have long speculated: it’s developing its own launch vehicles for its air-launch system, including a reusable space plane that could eventually carry people. pic.twitter.com/nF9lKVe4xk
— Jeff Foust (@jeff_foust) August 20, 2018
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.
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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- Stratolaunch’s Roc shown with a triplet of Orbital ATK Pegasus XL rockets. (Vulcan Space)
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- Back in 2012, SpaceX briefly entertained the idea of a Falcon 9 variant optimized for air-launch, potentially including crew rating the rocket down the road. (Stratolaunch/Dynetics)
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- The Roc is inconceivably vast. (Stratolaunch)
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.
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- A concept video produced by Stratolaunch shows the Roc launching a Kraken rocket. (Stratolaunch, via Wired)
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- A concept video produced by Stratolaunch shows the Roc launching a Kraken rocket. (Stratolaunch, via Wired)
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- A concept video produced by Stratolaunch shows the Roc launching a Kraken rocket. (Stratolaunch, via Wired)
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- SpaceX’s subscale Raptor engine has completed more than 1200 seconds of testing in less than two years. (SpaceX)
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- BFS (circa 2017) shows off its complement of SL and Vacuum Raptor engines. SpaceX is moving back to something similar to this. (SpaceX)
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.
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.
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News
Tesla removes Model S and X custom orders as sunset officially begins
In a significant development that marks the beginning of the end for two of its longest-running models, Tesla has removed the custom order configurator for the Model S sedan and Model X SUV from its website.
Tesla has officially started the “honorable discharge” of the Model S and Model X with a massive move, removing the two vehicles from Custom Orders and only offering inventory options.
It is the latest move Tesla has made to pull the Model S and Model X from its lineup, a decision CEO Elon Musk announced during its last quarterly earnings call.
Tesla brings closure to flagship ‘sentimental’ models, Musk confirms
In a significant development that marks the beginning of the end for two of its longest-running models, Tesla has removed the custom order configurator for the Model S sedan and Model X SUV from its website.
As of April 1, visitors to tesla.com/model-s and tesla.com/modelx are now redirected exclusively to limited inventory listings rather than a design studio, allowing buyers to select paint, wheels, interior options, or performance upgrades. Only pre-built vehicles currently in stock are available for purchase or lease.
Tesla CEO Elon Musk confirmed the change directly on X, posting: “Custom orders of the Tesla Model S & X have come to an end. All that’s left are some in inventory.”
Custom orders of the Tesla Model S & X have come to an end. All that’s left are some in inventory.
We will have an official ceremony to mark the ending of an era. I love those cars.
This was me at production launch 14 years ago: pic.twitter.com/6kvCf9HTHc
— Elon Musk (@elonmusk) April 1, 2026
We will have an official ceremony to mark the end of an era.” Accompanying the statement was a throwback photo from the Model S production launch in 2012, underscoring the emotional weight of the decision.
Musk had first signaled the phase-out during the company’s Q4 2025 earnings call in January, describing it as time for an “honorable discharge” of the programs to free up resources at the Fremont factory for Optimus humanoid robot production and autonomous vehicle initiatives.
The Model S, introduced in 2012, and the Model X, which followed in 2015, were instrumental in establishing Tesla as a premium electric vehicle leader.
The sedan offered class-leading range and acceleration, while the SUV’s signature falcon-wing doors became an iconic feature. Together, they proved EVs could compete in the luxury segment. Yet sales volumes have dwindled in recent years as Tesla prioritized higher-volume Model 3 and Model Y vehicles.
The flagships now represent a tiny fraction of overall deliveries, making continued custom production inefficient as the company accelerates toward robotaxis and next-generation platforms.
Prospective buyers are urged to act quickly. Remaining U.S. inventory vehicles—some nearly new—may include incentives such as lifetime free Supercharging, Full Self-Driving (Supervised) capability, and premium connectivity, depending on configuration.
Leasing options start around $1,699 per month for select Model X units, though exact pricing and availability fluctuate. International markets, including Europe and China, have already seen similar restrictions in recent months.
The move aligns with Tesla’s broader strategy to streamline its lineup and redirect manufacturing capacity toward autonomy and AI-driven products. While some enthusiasts lament the loss of personalization, the company views the transition as necessary progress.
Tesla has indicated that once the current inventory sells out, new Model S and Model X vehicles will no longer be offered.
For loyal owners and fans, the promised “official ceremony” may provide a fitting send-off. In the meantime, the website change serves as a clear signal: the era of bespoke flagship Teslas has quietly concluded, and the focus has fully shifted to the future.
Elon Musk
SpaceX files confidentially for IPO that will rewrite the record books
SpaceX files confidentially for a record-breaking IPO targeting a $1.75T valuation and $80B raise, driven by Starlink growth and its xAI merger.
Elon Musk’s rocket and satellite company submitted its draft registration to the U.S. Securities and Exchange Commission today for an initial public offering, targeting June at a $1.75 trillion valuation. This would be the largest in history.
SpaceX has filed confidentially with the SEC, first reported by Bloomberg. SpaceX would be valued above every S&P 500 company except Nvidia, Apple, Alphabet, Microsoft, and Amazon.
The filing uses a confidential process that allows companies to work through SEC disclosures privately before initiating a public roadshow. With a June target, official details through a formal prospectus is expected to go public in April or early May, after which SpaceX must wait at least 15 days before beginning investor marketing.
While SpaceX is best known for its Falcon 9 and Starship rockets, the $1.75 trillion valuation is anchored by Starlink, its satellite internet service. Starlink ended 2025 with 9.2 million subscribers and over $10 billion in revenue, which is a figure analysts project could reach a staggering $24 billion by the end of 2026. A February all-stock merger with xAI, Musk’s artificial intelligence venture, further boosted the valuation.
SpaceX officially acquires xAI, merging rockets with AI expertise
Bank of America, Goldman Sachs, JPMorgan Chase, and Morgan Stanley are lined up as senior underwriters. SpaceX is also considering a dual-class share structure to preserve insider voting control, and plans to allocate up to 30% of shares to retail investors, which is roughly three times the typical norm.
Elon Musk
Elon Musk hints at “official ceremony” with throwback photo to close Tesla Model S, Model X chapter
Elon Musk promises an official ceremony to mark the end of Tesla Model S and Model X production.
Tesla has officially begun winding down production of the Model S and Model X, sending farewell emails to U.S. customers on March 27 and updating the website to reflect the end of the line. Shoppers visiting Tesla.com now find only a limited set of Model S and Model X inventory units available for purchase, with no option to configure a new factory build. The move formalizes what CEO Elon Musk announced on the company’s Q4 2025 earnings call in January, when he said it was “time to basically bring the Model S and X programs to an end with an honorable discharge.”
Musk posted on X a throwback photo of himself speaking at the Model S production launch in 2012, and noting “We will have an official ceremony to mark the ending of an era. I love those cars.”
The mention of an official ceremony is notable. Tesla has not held a formal farewell event for a vehicle before, and Musk’s wording suggests this will be something deliberate rather than a quiet line shutdown. Given that Musk’s X post shows a photo of him on stage with a microphone in front of an audience at the Fremont factory, it wouldn’t be too far-fetched to expect a closing ceremony to take place at the same location. Perhaps? Whether it becomes a public event, a private gathering for employees, or a livestreamed moment on X remains to be seen.
Custom orders of the Tesla Model S & X have come to an end. All that’s left are some in inventory.
We will have an official ceremony to mark the ending of an era. I love those cars.
This was me at production launch 14 years ago: pic.twitter.com/6kvCf9HTHc
— Elon Musk (@elonmusk) April 1, 2026
The Model S first went on sale nearly fifteen years ago and was Tesla’s first fully in-house designed vehicle, proving that an electric car could be fast, desirable, and capable of long distance on a single charge. The Model X followed in 2015, turning heads with its unmistakable and distinctive falcon-wing doors, while becoming one of the first all-electric SUVs on the market. Tesla’s two flagship vehicles would ultimately push legacy automakers to take all-electric transportation seriously and help fund development of the more affordable Model 3 and Model Y.
By 2025, however, both models had been reduced to a rounding error in Tesla’s sales figures. Musk was direct about what comes next, stating “We are going to convert that production space to an Optimus factory. It’s part of our overall shift to an autonomous future.”
Elon Musk’s $10 Trillion robot: Inside Tesla’s push to mass produce Optimus
That shift is already underway. Tesla officially started Optimus Gen 3 production at its Fremont factory in January 2026, with the line targeting a run rate of one million units per year. The Gen 3 robot features 22 degrees of freedom per hand, runs on Tesla’s AI5 chip, and shares the same neural network architecture as Full Self-Driving. A dedicated Optimus factory at Gigafactory Texas is also under construction, with a planned annual capacity of 10 million units. The production lines that once built the Model S and Model X are being converted to support that ramp.
Tesla confirmed it will continue to support existing owners with service, software updates, and parts for as long as people own the vehicles. For buyers still interested in a new example, remaining U.S. inventory is discounted and the window is closing fast.
Tesla removes Model S and X custom orders as sunset officially begins
SpaceX files confidentially for IPO that will rewrite the record books
Elon Musk hints at “official ceremony” with throwback photo to close Tesla Model S, Model X chapter
Elon Musk says Tesla is developing a new vehicle: ‘Way cooler than a minivan’
Elon Musk launches TERAFAB: The $25B Tesla-SpaceXAI chip factory that will rewire the AI industry
