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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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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 gains massive vote of confidence on compensation plan for Elon Musk

“”The SBA supported Tesla’s 2018 performance award proposal and reaffirmed that support in the 2024 Tesla shareowner vote. The total return on Tesla’s stock after enactment of its 2018 performance award and the prior history of incentive structured plans leads us to strongly support the proposed 2025 CEO performance award.”

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Credit: Tesla

Tesla gained a massive vote of confidence on its proposed $1 trillion compensation plan for CEO Elon Musk from the State Board of Administration of Florida (SBA) on Monday.

On Monday, the SBA submitted a filing to the Securities and Exchange Commission (SEC) stating that it would vote to support Musk’s compensation plan, just as it did with the 2018 performance award and its second vote last year:

“The SBA supported Tesla’s 2018 performance award proposal and reaffirmed that support in the 2024 Tesla shareowner vote. The total return on Tesla’s stock after enactment of its 2018 performance award and the prior history of incentive structured plans leads us to strongly support the proposed 2025 CEO performance award. We believe the proposed award continues to promote an aggressive strategy to align incentives between management and shareowners and focuses solely on pecuniary factors and long-term shareowner value creation.”

This is the first large-scale shareholder that has come out and supported Musk’s potential compensation plan, which was outlined by Tesla and its Board of Directors earlier this month.

Most of the news surrounding Musk’s pay plan has been the opposite of what the SBA said today, as Institutional Shareholder Services (ISS) and Glass Lewis, two proxy firms, said they would be voting against the compensation package.

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Tesla Board Chair defends Elon Musk’s pay plan, slams proxy advisors

Musk replied to their vote last week during the Q3 Earnings Call, calling them “corporate terrorists.”

He said:

“I just don’t feel comfortable building a robot army here and then being ousted because of some asinine recommendations from ISS and Glass Lewis, who have no freaking clue. I mean, those guys are corporate terrorists. The problem, yeah. Let me explain, like, the core problem here is that so many of the index funds, passive funds, vote along the lines of whatever Glass Lewis and ISS recommend. They’ve made many terrible recommendations in the past. If those recommendations had been followed, they would have been extremely destructive to the future of the company.”

SBA’s perspective on the plan relies on what Musk has done in the past decade with Tesla, as he has driven company growth, increased shareholder value, and kept the company on track with its lofty and ambitious goals.

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It also outlined nine reasons to support Musk’s compensation:

  1. Pure Pay for Performance Design – Entirely Performance-Based, aligns with Shareowners
  2. Size of the Award and Share Count – Performance-based allocation, dilution tied to value creation, structured milestone design
  3. Market Capitalization Milestones – Clear, tiered targets, sustained performance requirement, shareholder value focus
  4. Operational/Product Milestones – Clear, quantifiable goals, strategic product focus, financial discipline, multi-quarter evaluation windows
  5. Vesting/Holding Periods – Long-term vesting structure, mandatory holding period, continuous service requirement
  6. CEO Succession – Succession planning requirement, performance integrity safeguard
  7. Time Horizon and Duration – Extended performance window of 10 years, no intermediate vesting
  8. Dilution & Voting Power Implications – Potential for significant ownership increase, permanent dilution
  9. Ambition and Stretch Goals – Extraordinary Scale of Growth, Shareowner value focus

Shareholders will vote on Musk’s compensation package on November 6 at the annual Shareholder Meeting.

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Tesla Optimus gets its latest job, and it’s not in the company’s factories

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Credit: Tesla Optimus | X

Tesla Optimus was spotted in its latest job placement, not at any of the company’s manufacturing or production facilities.

Optimus was instead spotted in New York City at Times Square, handing out Halloween candy to people:

It is not Tesla Optimus’s first gig in the service industry, as it has already secured several employment opportunities through the company’s projects. Last year, it served drinks at the company’s We, Robot day, where the Cybercab and Robovan were unveiled.

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Additionally, Optimus has been helping out at the Tesla Diner in Los Angeles, serving popcorn and greeting guests.

Elon Musk reveals big plans for Tesla Optimus at the Supercharger Diner

Optimus has many capabilities, and its applications can benefit both residential and commercial users. It is designed to be an at-home assistant, helping with tedious, monotonous tasks around the house.

In a commercial setting, Optimus will be programmed to handle everything from manufacturing to other factory-type tasks, as Tesla has already been using the robot in its own factories for smaller jobs.

Optimus has been in development for several years, but Tesla is ready to turn up the heat in terms of its capabilities and engineering as it prepares to launch it to a wider audience in the coming years.

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During the recent Q3 Earnings Call, Tesla CEO Elon Musk gave updates on the Optimus project, highlighting its progress and the company’s current development status.

Musk said that Tesla is “on the cusp of something really tremendous with Optimus, which I think is likely to be, has the potential to be, the biggest product of all time.” He also mentioned that Tesla is in an interesting position because not only has it established itself as one of the biggest car companies in the country, but it’s the only company that manufactures vehicles and has a monumental grasp of the importance of AI and robotics.

“I’m unaware of any robot program by Ford or GM or, you know, by U.S. car companies,” he said.

Musk added that Optimus has some pretty big responsibilities around Tesla’s factories:

“I mean, bringing Optimus to market is an incredibly difficult task, to be clear. It’s not like some walk in the park. At some point, I mean, actually, technically, Optimus can walk in the park right now. We do have Optimus robots that walk around our offices at our engineering headquarters in Palo Alto, California, basically twenty-four hours a day, seven days a week.”

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Right now, it appears Tesla is having its biggest challenge with the Optimus project around the development of its hands and forearms, which Musk called “an incredible thing” on the human body:

“The human hand is an incredible thing. The more you study the human hand, the more incredible you realize it is, and why you need four fingers and a thumb, why the fingers have certain degrees of freedom, why the various muscles are of different strengths, and fingers are of different lengths. It turns out that those are all there for a reason…Making the hand and forearm, because most of the actuators, just like the human hand, the muscles that control your hand are actually primarily in your forearm. The Optimus hand and forearm are an incredibly difficult engineering challenge. I’d say it’s more difficult than the rest of the robot from an electromechanical standpoint.”

Tesla is stumped on how to engineer this Optimus part, but they’re close

Optimus is starting to get more visibility in the public, and Tesla’s move to put it smack dab in the middle of New York City is one that will certainly bring some additional eyes to its development.

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Investor's Corner

Tesla analysts are expecting big things from the stock

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Credit: @AdanGuajardo/X

Tesla analysts are expecting big things from the stock (NASDAQ: TSLA) after many firms made price target adjustments following the Q3 Earnings Call.

Last Wednesday, Tesla reported earnings with record revenue but missed EPS estimates.

It blew delivery expectations out of the water with its strongest quarter in company history, but Tesla’s future relies on the development of autonomous vehicles, robotics, and AI, which many bullish firms highlight as major strengths.

The earnings call reiterated those points, along with the belief that Tesla CEO Elon Musk should be rewarded with a newly proposed pay package that would enable him to gain $1 trillion in wealth if he comes through on a lengthy list of performance tranches.

Nine Wall Street firms made adjustments to their outlook on Tesla shares in the form of price target increases since last Wednesday’s call, all of which are indications of big expectations for the stock moving forward.

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Here are the nine firms that made moves:

  • Truist – $280 to $406, reiterated Hold rating
  • Roth MKM – $395 to $404, reiterated Buy rating
  • Cantor Fitzgerald – $355 to $510, reiterated Overweight rating
  • Deutsche Bank – $435 to $440, reiterated Buy rating
  • Mizhuo – $450 to $485, reiterated Outperform rating
  • New Street Research – $465 to $520, reiterated Buy rating
  • Evercore ISI – $235 to $300, reiterated In Line rating
  • Freedom Capital Markets – $338 to $406, upgraded to Hold rating
  • China Renaissance – $349 to $380, reiterated Hold rating

The boosts in price target are largely due to Tesla’s future projects, as Roth MKM, Cantor Fitzgerald, Mizuho, New Street Research, and Evercore ISI all explicitly mention Tesla’s autonomy, robotics, and AI potential as the main factors for its price target boosts.

Cantor Fitzgerald raises Tesla PT To $510, citing Cybercab, Semi, and AI momentum

It is no surprise that many firms are adjusting their outlook on Tesla shares considerably in an effort to prepare for the company’s transition to even more of a tech company than a car company.

The issue with many analysts is that they treat the company’s vehicle deliveries as the main indicator of value.

However, Tesla has a robust energy division, which was a major contributor to the company’s strong margins and gross profit in Q3, as well as its prowess in robotics and AI.

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Additionally, the company is seen as a key player in the autonomy field, especially after launching driverless rides on a Robotaxi platform in Austin and expanding a similar program in the Bay Area.

Tesla shares were up over 5 percent at 12:18 p.m. on the East Coast.

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