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Ex-SpaceX engineer leads Stratolaunch to major rocket engine test milestone

Stratolaunch has successfully completed the first full-scale test of its 200,000-lbf thrust PGA rocket engine. (Stratolaunch)

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7 years ago

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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.

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.

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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.

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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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 Cybertruck gets Full Self-Driving v14 release date, sort of

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11 hours ago

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October 7, 2025

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Tesla Cybertruck owners are wondering when they will get access to the company’s Full Self-Driving version 14.1 that rolled out to other owners today for the first time.

Cybertruck owners typically receive Full Self-Driving updates slightly later than other drivers, as the process for the all-electric pickup is different. It is a larger vehicle that requires some additional attention from Tesla before FSD versions are rolled out, so they will be slightly delayed. CEO Elon Musk said the all-wheel steering technically requires a bit more attention before rollout as well.

After some owners got access to the v14.1 Full Self-Driving suite this morning, Cybertruck owners sought out a potential timeframe for when they would be able to experience things for themselves.

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Tesla owners show off improvements with new Full Self-Driving v14 rollout

They were able to get an answer from Ashok Elluswamy, Tesla’s Head of AI, who said:

“We got you. Coming soon.”

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The release of FSD v14.1 for Cybertruck will not be tempered, either. Elluswamy then confirmed that Tesla would be rolling out the full-featured FSD v14 for the pickup, meaning it would be able to reverse and park itself, among other features.

Elluswamy said it would be capable of these features, which were void in other FSD releases for Cybertruck in the past.

Tesla’s rollout of FSD v14.1 brings several extremely notable changes and improvements to the suite, including more refined operation in parking garages, a new ability to choose parking preferences upon arriving at your destination, a new driving mode called “Sloth,” which is even more reserved than “Chill,” and general operational improvements.

Those who were lucky enough to receive the suite have already started showing off the improvements, and they definitely seem to be a step up from what v13’s more recent versions were capable of.

CEO Elon Musk called v14 “sentient” a few weeks back, and it seems that it is moving toward that. However, he did state that additional releases with more capabilities would be available in the coming weeks, but many owners are still waiting for this first version.

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Tesla launches two new affordable models with ‘Standard’ Model 3, Y offerings

It is the first time Tesla has revealed any details about what it planned to launch in terms of its new, lower-cost vehicles, which are mainly aimed at countering the loss of the $7,500 EV tax credit.

Published

14 hours ago

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October 7, 2025

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Credit: Tesla

Tesla has officially launched its affordable models with the new Model 3 and Model Y ‘Standard’ versions hitting the company’s Online Design Studio on Tuesday.

It is the first time Tesla has revealed any details about what it planned to launch in terms of its new, lower-cost vehicles, which are mainly aimed at countering the loss of the $7,500 EV tax credit.

Here’s what Tesla went with for its release of the new affordable models.

Tesla Model Y ‘Standard’

The Model Y Standard is a stripped-down version of the all-electric crossover and starts at $39,990.

Deliveries are slated for November and December, the company says if you plan to order one, and it comes with a few major changes to improve efficiency and bring down cost for owners.

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  • New athletically tuned exterior and new alloy wheels to improve aerodynamics
  • 15.4″ touchscreen in the front, the same as the other trims
  • Available in three colors: Stealth Grey (free), White ($1,oo0 extra), Diamond Black ($1,500 extra)
  • Textile and vegan leather interior
  • Range sits at 321 miles
  • New front fascia
  • Covered glass roof (textile on inside)
  • Windows are not acoustically laminated for a quieter cabin
  • Manual mirrors and seats
  • Smaller frunk
  • No rear infotainment screen
  • No basic Autopilot
  • 69 kWh battery
  • New 19″ Aperture wheels
  • 0-60 MPH in 6.8 seconds
  • 7 speaker stereo, down from 15 speakers in premium models

Tesla Model 3 ‘Standard’

The Model 3 Standard was a surprise offering from Tesla, as many had only anticipated the company to refine and offer a more affordable version of the Model Y.

Coming in at $36,990, it features many of the same changes Tesla made with the Model Y “Standard,” all ways to improve price and make it less flashy than the more premium offerings.

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Deliveries are also slated for November for this vehicle, and it features relatively the same stripped-down offerings as the Model Y Standard.

  • Available in three colors: Stealth Grey (free), White ($1,oo0 extra), Diamond Black ($1,500 extra)
  • Textile and vegan leather interior
  • Range sits at 321 miles
  • Covered glass roof (textile on inside)
  • Manual mirrors and seats
  • No rear infotainment screen
  • No basic Autopilot
  • 69 kWh battery
  • New 19″ Aperture wheels
  • 0-60 MPH in 6.8 seconds
  • 7 speaker stereo, down from 15 speakers in premium models
@teslarati 🚨 Tesla’s Affordable Models are here! Let’s talk about them! #tesla #fyp #viral #teslaev #elonmusk ♬ Natural Emotions – Muspace Lofi

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Tesla owners show off improvements with new Full Self-Driving v14 rollout

Some of the big things that Tesla faced head-on with the development and release of v14 were navigating in parking garages and handling parking after arriving at a destination.

Published

16 hours ago

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October 7, 2025

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Credit: Tesla Europe & Middle East/X

Tesla owners with access to the company’s Full Self-Driving new version, v14, which rolled out on Tuesday morning, are showcasing some of the very impressive improvements that have arrived.

CEO Elon Musk called v14 “sentient” a few weeks ahead of its rollout, claiming the newest iteration of the company’s Full Self-Driving platform would be the most accurate to date.

Tesla FSD (Supervised) V14.1 with Robotaxi-style dropoffs is here

It was obvious this narrative had Tesla owners keeping their expectations high, as there were very evidently things that needed to be improved upon that were present in v13. I wrote about several improvements I was hoping to see, and based on the release notes for v14, Tesla did have these things in the works already.

Some of the big things that Tesla faced head-on with the development and release of v14 were navigating in parking garages and handling parking after arriving at a destination.

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Tesla said it was working to increase the capabilities of Summon within parking garages, as many owners believe that is where it would be the most beneficial.

While that does not appear to be part of this initial v14 rollout, it does seem Tesla is focused on improving the suite’s ability to navigate through these garages, including stopping for a ticket to enter the facility, finding a spot, and parking in an appropriate space.

It was evident this was a huge improvement based on one example from an owner who received v14:

If you look closely, you will even see the car shift slightly to the right when it arrives at the ticketing station, making it easier for the driver to hand over their ticket and payment. It then moves back out to the right when leaving to return to the center of the lane. It’s very intuitive.

Additionally, it appears to be more accurate when parking, thanks to improvements that enable owners to select the type of parking upon arrival at a destination.

In the v14.1 release notes, Tesla said that it has added “Arrival Options for you to select where FSD should park: in a Parking Lot, on the Street, in a Driveway, in a Parking Garage, or at the Curbside.”

One owner chose to navigate home and chose a garage to park in. Full Self-Driving performed it without any issues:

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These are just two evident improvements so far, and there are likely many more on the way. The changes and fixes will be tracked by anyone with access to FSD v14 in the coming weeks.

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