News
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
-
- Stratolaunch’s Roc shown with a triplet of Orbital ATK Pegasus XL rockets. (Vulcan Space)
-
- 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)
-
- 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.
-
- A concept video produced by Stratolaunch shows the Roc launching a Kraken rocket. (Stratolaunch, via Wired)
-
- A concept video produced by Stratolaunch shows the Roc launching a Kraken rocket. (Stratolaunch, via Wired)
-
- A concept video produced by Stratolaunch shows the Roc launching a Kraken rocket. (Stratolaunch, via Wired)
-
- SpaceX’s subscale Raptor engine has completed more than 1200 seconds of testing in less than two years. (SpaceX)
-
- 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.
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!
SpaceX’s Raptor engine family has steadily increased sea-level thrust while simultaneously reducing mass, turning iterative engineering gains into substantially higher performance for the Super Heavy booster. CEO Elon Musk shed more light on how powerful Raptor 4 will be, and it’s pretty crazy.
Raptor 1 delivered 185 metric tons of thrust at roughly 2,080 kilograms, while Raptor 2 raised that to 230 tons while cutting mass to about 1,630 kilograms. SpaceX data for Raptor 3 lists a target of 280 tons at 1,525 kilograms (with further reductions in associated vehicle hardware), while operational flight ratings have been cited near 250 tons.
This morning, Elon Musk stated that Raptor 4 is expected to reach 300 tons of sea-level thrust at roughly the same mass as Raptor 3. Across these versions, thrust has risen by more than 60 percent from the first engines while engine mass has fallen, producing a sharp improvement in thrust-to-weight ratio. This is a true testament to how great SpaceX engineering has been:
🚀 Elon says Raptor 4 will make 300 tons of thrust at sea level at roughly the same mass as Raptor 3.
How far Raptor has come:
Raptor 1: 185 tf, 2,080 kg
Raptor 2: 230 tf, 1,630 kg
Raptor 3: 250 tf, 1,525 kg
Raptor 4: 300 tf33 on Super Heavy = ~9,900 tf, nearly 3x Saturn V https://t.co/HQDswZhyvL
— TESLARATI (@Teslarati) October 26, 2026
With 33 engines on SuperHeavy, the jump from earlier versions to a 300-ton Raptor 4 would produce roughly 9,900 metric tons of total liftoff thrust, nearly three times the Saturn V’s approximately 3,400 metric tons from its five F-1 engines.
This is not just a larger number on a data sheet, either, as sea-level thrust is the force available the moment the vehicle leaves the pad. This is when it is heaviest and still deep in Earth’s gravity well and dense atmosphere.
Higher levels of sea-level thrust directly improves the initial thrust-to-weight ratio of the full stack. A higher ratio produces faster acceleration off the pad, which shortens the time the rocket has to spend fighting gravity, and gravity losses during the first minute or two of the flight are a major drain on total available delta-v. Every second shaved off of that early climb preserves more propellant energy for reaching orbital velocity or for carrying extra payload.
Because Super Heavy’s engine count is constrained by vehicle diameter and packing density, increasing thrust per engine is the most straightforward way to raise total liftoff performance without redesigning the booster structure or design.
The same-mass target for Raptor 4 is equally important. Holding engine mass roughly constant while raising thrust improves the engine’s own thrust-to-weight ratio and reduces the structural and propellant mass fraction that must be carried solely to support the engines.
Earlier Raptor iterations also simplified or eliminated extensive vehicle-side hardware such as heat shields. These gains compound: more force for less installed mass leaves additional capacity for propellant, payload, or operational margins such as engine-out capability.
For Starship’s architecture, the practical effects are large. Greater liftoff thrust supports heavier vehicles, larger propellant loads, and higher payloads to low Earth orbit, figures SpaceX has targeted in the 100-plus-ton reusable range. That capacity underpins orbital refueling, lunar missions, and eventual Mars cargo and crew flights.
Continued growth in sea-level thrust therefore tightens the gap between theoretical rocket performance and the high flight rates and reusability needed to make large-scale space transport practical.
Tesla has expanded its Tesla Assisted Driving (TAD) suite to its tenth European country, as Latvia joined a growing list of European Union member states authorizing the company’s advanced driver assistance technology.
Tesla Europe announced this morning that the system is now approved in Latvia, with a software rollout to begin soon.
The approval and rollout follow recognition of a provisional European type approval originally granted by the Netherlands’ RDW authority on April 10.
🚨 Latvia has just received approval for Tesla Full Self-Driving (Supervised)
This is the 10th country in the EU to gain approval:
1. Netherlands — 10 April 2026 (original RDW approval)
2. Lithuania — 20 May 2026
3. Estonia — 29 May 2026
4. Denmark — 9 June 2026
5. Belgium — 10 June 2026
6. Slovenia — 7 September 2026
7. Czechia — 21 September 2026
8. Croatia — 29 September 2026
9. Slovakia — 16 October 2026— TESLARATI (@Teslarati) October 26, 2026
Latvia’s Road Traffic Safety Directorate (CSDD) evaluated the Dutch documentation, coordinated with the other national authorities, and reviewed updates from Tesla. These included tightened limits on speed offsets, automatic resets of any manual speed adjustments after each trip, and stronger driver monitoring.
In Europe, the feature is marketed as Tesla Assisted Driving after a recent rule change that labeled the name “Full Self-Driving” as misleading.
The system remains an SAE Level 2 driver assistance tool, not unsupervised autonomy. It can control speed, steering, braking, lane changes, and intersections while following a navigation route. Drivers need not keep their hands on the wheel at all times, yet they must continuously monitor the road and be prepared to intervene immediately.
The sequence of EU recognitions began with the Netherlands in April and continued through Lithuania, Estonia, Denmark, Belgium, Slovenia, Czechia, Croatia, and Slovakia. Most have relied on mutual recognition of the single Dutch provisional approval rather than independent national testing.
These national clearances do not yet constitute bloc-wide authorization. An EU-wide decision requires a qualified majority in the Technical Committee on Motor Vehicles: at least 15 of 27 member states representing 65 percent of the EU population. Larger markets, like Germany, France, and Italy, remain under review, and a vote is expected this December.
However, for Latvian Tesla owners with compatible vehicles and software, the imminent rollout expands access to the supervised system while underscoring that attentive human oversight remains essential.
Tesla expanded its Robotaxi geofence in Houston, Texas, today, enlarging the service area and drawing a new rocket-shaped boundary across the city’s northwestern and central parts.
Although CEO Elon Musk said it was just a coincidence, the expansion seems to be an ode to SpaceX and its potential merger with Tesla.
🚨 Tesla has just expanded its Robotaxi geofence in Houston
It looks a lot like a rocket — we all remember the shape in Austin 🤣 https://t.co/cFOPEuiJ4u
— TESLARATI (@Teslarati) October 26, 2026
The official Tesla Robotaxi account announced the change with the lines “Houston, we have liftoff” and “Bigger service area now live,” pairing them with a map overlay.
The prior white geofence, roughly 25 square miles covering Jersey Village, Harvest Bend, and the Willowbrook corridor along U.S. 290 and State Highway 249, now sits inside a larger blue zone that stretches southeast toward Bellair and closer to central Houston.
Houston’s Robotaxi service launched on April 18, 2026, the same day as Dallas, as Tesla’s first unsupervised public expansion beyond Austin. From the start, the vehicles were Model Ys running without anyone in the front seats, booked through the dedicated Tesla Robotaxi app and open to the public inside the geofence.
Trackers measured the initial zone at about 25 square miles; by late September it had not grown substantially. Community and registry data indicated a modest local fleet of unsupervised Model Ys, while dozens to nearly 200 Cybercabs, the purpose-built, steering-wheel-free two-seaters, have been spotted staging and testing in Houston lots, though public Cybercab rides remain limited to Austin for now.
Across the broader Robotaxi program, Tesla began public Robotaxi rides in Austin in June 2025, as a small geofence and vehicles with safety monitors became available for a ride-hailing service. Later on, Tesla removed the monitors and steadily expanded the service area until it covered most of the Austin metro area.
Unsupervised Robotaxi services now run in six cities: Austin, Dallas, Houston, Miami, Orlando, and Tampa. Cumulative driverless miles reported by the company have reached several million. The Cybercab entered public service in Austin in early September 2026 and has scaled rapidly there. The company has also said that Dallas is next for Cybercab rides in November, with further cities and 24/7 hours targeted by year-end, plus fleet-operator sales of the vehicle.
Waymo also operates a fully driverless service in Houston, which has been open to the public since August of this year.
The Houston expansion continues Tesla’s pattern of starting with tightly controlled validation zones before widening coverage as real-world data accumulates, while the rocket motif on the map underscores the company’s habit of injecting visual flair into its autonomy rollout.
Riders inside the new boundary can request unsupervised Model Y trips in the Robotaxi app; exact operating hours and further Cybercab availability remain subject to app updates and company statements.
How SpaceX Is raising Raptor’s sea-level thrust while holding engine mass steady
Tesla Assisted Driving expands to tenth EU country
