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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.
- A to-scale comparison of Falcon 1, Pegasus XL, MLV, and Falcon 9. (Teslarati/Stratolaunch/Wikipedia)
- 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.
- PGA’s first full-scale preburner seen during assembly. (Stratolaunch)
- PGA’s first full-scale preburner seen during assembly. (Stratolaunch)
- Jeff Thornburg stands in front of Stratolaunch’s NASA Stennis Space Center test stand. (Stratolaunch)
- The PGA preburner seen after installation at Stennis. (Stratolaunch)
- The control center. (Stratolaunch)
- MLV is released from Stratolauncher. (Stratolaunch)
- A concept video produced by Stratolaunch shows the Roc launching a Kraken rocket. (Stratolaunch, via Wired)
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Tesla just unlocked sales to 50,000+ government agencies
It marks a significant step in expanding Tesla’s presence in the public sector, where procurement processes have traditionally slowed electric vehicle adoption.
Tesla just unlocked sales to over 50,000 government agencies by entering a new agreement with Sourcewell, a purchasing cooperative.
Tesla entered a new master purchasing agreement with Sourcewell, the largest government purchasing cooperative in the U.S. This will enable streamlined sales of its EVs to more than 50,000 U.S. public entities. Tesla entered Designated Contract 0813525-TES, and the agreement covers Model 3, Model Y, and Cybertruck, and potentially other vehicles the company could release.
It marks a significant step in expanding Tesla’s presence in the public sector, where procurement processes have traditionally slowed electric vehicle adoption.
The deal allows eligible agencies, including cities, school districts, state governments, and higher-education institutions, to purchase Tesla vehicles directly through Sourcewell without conducting their own lengthy competitive bidding or request-for-proposal (RFP) processes.
Pricing is pre-negotiated and capped, providing transparency and predictability. Agencies simply register for a Sourcewell account online or by phone and place orders under the existing contract. This cooperative model aggregates demand across thousands of members, reducing administrative costs and time while ensuring compliance with public procurement rules.
For Tesla, the agreement removes major barriers to government fleet sales. Public-sector procurement cycles often stretch 12 to 18 months due to bidding requirements and committee reviews.
Tesla buyers in the U.S. military can get $1,000 off Cybertruck purchases
By securing the master contract, Tesla gains immediate, simplified access to a massive customer base that previously faced friction in adopting EVs. The company highlighted in its announcement that the partnership will help these 50,000-plus agencies “save thousands of $$$ in operating costs for their vehicle fleet over time” through lower maintenance, energy efficiency, and the elimination of tailpipe emissions.
The initial four-year term runs through November 13, 2029, with options for up to three one-year extensions, offering long-term stability for both parties.
Sourcewell’s role is central to execution. As a cooperative purchasing organization, it negotiates and manages vendor contracts on behalf of its members, then makes them available nationwide. Participating entities contact Tesla’s dedicated fleet team or Sourcewell representatives to complete purchases, bypassing redundant paperwork.
This structure accelerates fleet electrification while maintaining fiscal accountability—agencies receive pre-vetted pricing and terms without reinventing the wheel for each vehicle order.
The partnership positions Tesla to capture a larger share of the public fleet market, where total cost of ownership often favors electric vehicles once procurement hurdles are removed.
For government buyers, it translates to faster deployment of sustainable fleets, reduced long-term expenses, and alignment with environmental mandates. As more agencies transition, the contract could contribute to broader EV infrastructure growth and taxpayer savings across the country.
Elon Musk
How much of SpaceX will Elon Musk own after IPO will surprise you
SpaceX’s IPO filing confirms Musk will maintain his voting power to make key decisions for the company.
Elon Musk will retain dominant voting control of SpaceX after it goes public, according to the company’s IPO prospectus that was filed with the SEC. The filing reveals a dual-class equity structure giving Class B shareholders 10 votes each, concentrating power with Musk and a handful of other insiders, while Class A shares sold to public investors carry one vote.
Musk holds approximately 42% of SpaceX’s equity and controls roughly 79% of its votes through super-voting shares. He will simultaneously serve as CEO, CTO, and chairman of the nine-member board after the listing. Beyond that, the filing includes provisions that may limit shareholders’ influence over board elections and legal actions, forcing disputes into arbitration and restricting where they can be brought.
The case for Musk holding this level of control is grounded in SpaceX’s actual history. The company’s most important bets, from reusable rockets to a global satellite internet constellation, were decisions that ran against conventional aerospace thinking and would likely have faced resistance from a board accountable to investor gains. Fully reusable rockets were considered economically irrational by established industry players for years. Starlink, which now generates over $4 billion in annual operating profit, was widely dismissed as financially unviable when it was proposed. The argument for concentrated founder control seems straightforward, and the decisions that built SpaceX into what it is today required someone willing to ignore consensus and absorb years of losses.
SpaceX files confidentially for IPO that will rewrite the record books
For context, Musk’s position is significantly more dominant than Zuckerberg’s at Meta. The comparison with Tesla is also worth noting. When Tesla did its IPO in 2010, it did not issue dual-class shares. Musk has only recently pushed for enhanced voting protection, proposing at least 25% control at Tesla in 2024 after selling shares to fund his Twitter acquisition left him with around 13%.
SpaceX has clearly learned from that experience and structured the IPO differently by planning to allocate up to 30% of shares to retail investors, roughly three times the typical norm for a large offering. The roadshow is expected to begin the week of June 8, with a Nasdaq listing rumored to be a $1.75 trillion valuation and a $75 billion raise.
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Tesla bolsters App with new safety, insurance, and storage features
The Tesla Smartphone App is one of the biggest and best features and advantages owners have. Everything from moving the vehicle with Summon, to getting Navigation sent to the car, to preconditioning the cabin can be done with the Tesla App.
Tesla is bolstering its smartphone App with a series of new features to streamline operations for owners. The new additions include fixes to safety, its in-house insurance offering, and storage management for Dashcam clips.
The Tesla Smartphone App is one of the biggest and best features and advantages owners have. Everything from moving the vehicle with Summon, to getting Navigation sent to the car, to preconditioning the cabin can be done with the Tesla App.
But in classic Tesla fashion, the company is aiming to improve the offerings of the app, and it is doing so with a handful of new features. They were first discovered by Tesla App Updates.
Tesla Insurance – Safety Score 3.0
This is truly part of the Spring 2026 Update, but Tesla has now given more transparency on how FSD has saved people money on their premiums.
Tesla intertwines FSD with in-house Insurance for attractive incentive
Additionally, Tesla is now automatically awarding a Safety Score of 100 for every mile traveled on Full Self-Driving (Supervised).
Update Tracking
Updates traditionally appear on the App or on the Center Touchscreen in the car. There is nothing better than seeing that Green Arrow at the top of the screen, or opening your app and seeing that there is a Software Update available.
Now, there will be no need to manually check the app and initiate the download. Tesla is enabling a new feature that will automatically download updates for you.
Storage Management
Your USB drive can now be remotely formatted, and old Dashcam clips can be deleted straight from the phone. When you record a lot of things using the Dashcam feature, that storage fills up pretty quickly.
Now, manually deleting the Dashcam videos is easier than ever.
Trailer Light Test
This is perhaps the coolest and most crucial addition to the Tesla App, as those who tow and haul will now be able to trigger a diagnostic light sequence from the app while standing behind your trailer to ensure the brake lights work.
Verifying your trailer lights are connected properly and operating normally and as intended is normally a massive hassle.
Now, a new trigger will be available to initiate a diagnostic light sequence directly from your phone.








