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SpaceX’s Starship Raptor Vacuum engine plans laid out by CEO Elon Musk

A 2016 render of Raptor Vacuum. Much has changed about the engine's design in the three years since, but SpaceX is still pursuing a vacuum variant. (SpaceX)

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Elon Musk says that SpaceX Starship engine upgrades are on track to begin static fire tests of a Raptor Vacuum variant as few as a “couple months” from now.

Designed to enable more efficient performance in thin atmosphere or vacuum, Musk admitted that the first version(s) of Raptor Vacuum (RVac) will likely be a compromise between efficiency and speed of development. Nevertheless, the faster SpaceX can prepare Raptor Vacuum for flight, the easier it will be for Starship to begin serious (sub)orbital flight tests.

As it turns out, SpaceX’s first and only official render of Raptor – published in September 2016 – showed the engine’s vacuum-optimized variant. In the years since, CEO Elon Musk has vacillated between keeping the vacuum engines as a central Starship feature and simply replacing them with regular sea level Raptors to expedite the spacecraft’s debut. The 2016 and 2017 vehicles featured a mixture of vacuum and sea-level engines, whereas Musk revealed a vehicle with sea-level engines only in 2018.

Known as the Interplanetary Transport System in 2016, the ship featured six vacuum Raptors and 3 SL engines. (SpaceX)
In 2017, Big Falcon Spaceship shrunk and changed to 4 x RVac and 3x x Raptor SL engines. (SpaceX)
In 2018, Musk decided to sidestep vacuum engines entirely, moving to 7 SL Raptors. (SpaceX)

Perhaps less than a month after Musk’s September 2018 presentation, the SpaceX CEO made the decision to radically redesign the vehicle – newly christened Starship and Super Heavy – by moving from a carbon composite aerostructure to stainless steel. At first, the seven SL Raptors remained a part of the design, but Musk took to Twitter in 2019 to indicate that SpaceX had changed gears again and had reprioritized Raptor Vacuum development.

This came as a bit of surprise and it should go without saying that there’s a significant chance that Musk/SpaceX will oscillate in the opposite direction once again before Raptor Vacuum is actually ready for flight. This time, though, Musk has sketched out a development schedule and strategy that suggests SpaceX is much more serious this time.

Most notably, Musk claims that the first Raptor Vacuum prototype could be ready for static fire testing just a “couple months” from now, an immensely ambitious schedule for any large liquid rocket engine development program. Nevertheless, Musk did indicate that the “V1.0” Raptor Vacuum design would be significantly compromised and “suboptimal”, an intentional decision to prioritize the engine’s “speed of development”.

Even then, Musk believes that the first variant – featuring a shortened bell nozzle – could still be up to 12% more efficient than sea level Raptors and thus already 70-80% of the way to the physical limit of methane-oxygen rocket efficiency.

A sea-level Raptor engine is static-fired at SpaceX’s McGregor, TX test facilities. (SpaceX)

On a positive note, shrinking V1.0 Raptor Vacuum’s nozzle a bit from its nominal length will likely mean that SpaceX can static fire fully-integrated engines at its McGregor, TX test facilities, critical for speedy development. If not, the company has experience with alternatives through Merlin Vacuum, which can only be tested on the ground with its lengthy nozzle detached. This method just makes it dramatically harder to optimize a vacuum nozzle design, as full-scale, flight-like testing is nearly impossible if a given vacuum engine can’t be tested on the ground with said nozzle installed.

Vacuum engines need such large and unwieldy nozzles in order to make them as efficient as possible. In a very simplistic sense, a rocket engine nozzle directs the flow of superheated, ultrafast gases in order to squeeze as much momentum transfer as possible out of available propellant. The lower the pressure of the surrounding atmosphere is, the more those gases will expand immediately after leaving the nozzle – giant vacuum nozzles simply try to harness the additional momentum available from that extra expansion. This is why rocket exhausts appear to spread and thin out as launch vehicles reach higher and higher altitudes.

A Falcon 9 upper stage’s vacuum nozzle glows white hot during an orbital MVac burn. (SpaceX)

In this sense, the perfect theoretical vacuum nozzle is quite literally infinitely long. The job of vacuum rocket engineers is to find the perfect balance between that impractical theoretical perfection and the limits of real-world materials and dynamics. In theory, SpaceX’s sea-level Raptor engines have already been designed to operate in vacuum conditions, while the engine’s closed-cycle design and regeneratively (i.e. propellant) cooled nozzle should apply well to a vacuum design.

If SpaceX is lucky, there will be few roadblocks in the way of simply lengthening a SL Raptor-style nozzle and calling it a day, in which case it would be impressive but not all that surprising if SpaceX is actually able to begin RVac testing before the end of 2019. Once a rough V1.0 engine is in place, the process of optimizing efficiency can be done slowly and methodically, all while exploiting an unprecedented wealth of data from flight and orbit-tested Raptor Vacuum engines.

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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 board reveals reasoning for CEO Elon Musk’s new $1 trillion pay package

“Yes, you read that correctly: in 2018, Elon had to grow Tesla by billions; in 2025, he has to grow Tesla by trillions — to be exact, he must create nearly $7.5 trillion in value for shareholders for him to receive the full award.”

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(Credit: Tesla)

Tesla’s Board of Directors has proposed a new pay package for company CEO Elon Musk that would result in $1 trillion in stock offerings if he is able to meet several lofty performance targets.

Musk, who has not been meaningfully compensated since 2017, completed his last pay package by delivering billions in shareholder value through a variety of performance-based “tranches,” which were met and resulted in the award of billions in stock.

Elon Musk’s new pay plan ties trillionaire status to Tesla’s $8.5 trillion valuation

However, Musk was unable to claim this award due to a ruling by the Delaware Chancery Court, which deemed the payout an “unfathomable sum.”

Now, the company is taking steps to ensure Musk gets paid, as the Board feels that it is crucial to retain its CEO, who has been responsible for much of the company’s success.

This is not a statement to undermine the work of all of Tesla’s terrific employees, but a ship needs to be captained by someone, and Musk has proven he is the right person for the job.

The Board also believes that, based on a statement made by the company in its proxy, various issues will be discussed during the upcoming Shareholder Meeting.

Robyn Denholm and Kathleen Wilson-Thompson recognized Musk’s contributions in a statement, which encouraged shareholders to vote to approve the payout:

“We’re asking you to approve the 2025 CEO Performance Award. In designing the new performance award, we explored numerous alternatives. Ultimately, the new award aims to build upon the success of the 2018 CEO Performance Award framework, which ensure that Elon was only paid for the performance delivered and incentivized to guide Tesla through a period of meteoric growth. The 2025 CEO Performance Award similarly challegnes Elon to again meet a series of even more aspirational goals, including operational milestones focused on reaching Adjusted EBITDA targets (thresholds that are up to 28 times higher than the 2108 CEO Performance Award’s top Adjusted EBITDA milestone) and rolling out new or expanded product offerings (including 1 million Robotaxis in commercial operation and delivery of 1 million AI Bots), all while growing the company’s market capitalization by trillions of dollars.

Yes, you read that correctly: in 2018, Elon had to grow Tesla by billions; in 2025, he has to grow Tesla by trillions — to be exact, he must create nearly $7.5 trillion in value for shareholders for him to receive the full award.

In addition to these unprecedented performance milestones, the 2025 CEO Performance Award also includes innovative structural features, born out of the special committee’s considered analysis and extensive shareholder feedback. These features include supercharged retention (at least seven and a half years and up to 10 years to vest in the full award), structural protections to minimize stock price volatility due to administration of this award and, thereafter, incentives for Elon to participate in the Board’s continued development of a framework for long-term CEO Succession. If Elon achieves all the performance milestones under this principle-based 2025 CEO Performance Award, his leadership will propel Tesla to become the most valuable company in history.”

Musk will have a lot of things to accomplish to receive the 423,743,904 shares, which are divided into 12 tranches.

However, the Board feels he is the right person for the job, and they want him to remain the CEO. This package should ensure that he stays with Tesla, as long as shareholders feel the same way.

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Tesla Robotaxi app download rate demolishes Uber, Waymo all-time highs

After two and a half months of testing with a group of hand-picked Tesla influencers and some media, the company has officially launched Robotaxi rides in both Austin, Texas, and the California Bay Area to the public.

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Credit: @BLKMDL3 | X

Tesla launched its Robotaxi app to the general public yesterday, and the number of downloads is a testament to the platform’s high demand for testing.

After two and a half months of testing with a group of hand-picked Tesla influencers and some media, the company has officially launched Robotaxi rides in both Austin, Texas, and the California Bay Area to the public.

Tesla Robotaxi makes major expansion with official public app launch

Downloading the app is available to iOS users, so if you have an iPhone, you can get it and join the waitlist. Tesla has not yet launched the Robotaxi app for the Android platform, but did hint that it would be coming soon.

The testing phase with the group Tesla selected has gone well. In Austin, the City has only listed one “Safety Concern” with Robotaxi during the testing phase. For the most part, things have gone extremely well, and riders have had good things to say.

Tesla is still operating with some safeguards in place, such as Safety Monitors and Safety Drivers, but these are precautionary and temporary; CEO Elon Musk has said they should be removed by the end of the year.

Elon Musk says Tesla will take Safety Drivers out of Robotaxi: here’s when

Even still, Tesla Robotaxi is something that many people want to experience, and the app downloads prove it.

The Tesla Robotaxi app was downloaded at a rate that exceeded all rolling 30-day periods of both Uber and Waymo, according to Brett Winton of ARK Invest. Tesla’s Robotaxi’s first day on the App Store exceeded Uber’s by 40 percent and Waymo’s best download day ever by six times:

The surge in downloads is a good indication of how in demand the Robotaxi suite was, as many people within the community had vocalized their requests to try the platform, but Tesla was not ready to expand it beyond its handpicked group.

The expansion of the program will result in more rides, provided Tesla continues to expand its fleet of vehicles. It has already admitted many of those who were initially placed on the waitlist.

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Elon Musk’s xAI expands to Seattle with salaries up to $440,000

The move was announced by the artificial intelligence startup and Elon Musk on social media platform X.

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(Credit: xAI)

Elon Musk’s artificial intelligence startup xAI is opening a new office in Seattle as it accelerates its global expansion. 

The move was announced by the artificial intelligence startup and Elon Musk on social media platform X. xAI is also hiring for its first positions in the new site.

New Seattle office

As could be seen on xAI’s Careers webpage, the Seattle office is currently hiring for three engineering roles. Each of the three technical roles tied to the new site carry salaries ranging from $180,000 to $440,000. 

The new office adds to xAI’s growing presence, which now spans San Francisco, Austin, London, Dublin, New York, and Memphis. The Seattle-based roles focus on video and image generation systems, signaling Musk’s intent to challenge rivals like OpenAI and Meta in generative AI.

Pressures and challenges

Seattle also places xAI within reach of Microsoft’s headquarters in Redmond. Microsoft has emerged as a central player in the AI race through its multibillion-dollar partnership with OpenAI, making xAI’s move into the region notable. The competition for AI specialists has pushed salaries higher across the industry, with filings showing OpenAI staff earning up to $530,000 and Anthropic engineers as much as $690,000 annually, as noted by Insider.

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The startup has also seen some high-profile departures in recent months, including cofounder Igor Babuschkin and general counsel Robert Keele. Still, xAI continues to grow aggressively, and its Grok large language model has been gaining momentum among mainstream users. Work also continues to be underway to further build out the company’s Colossus supercomputer cluster. Reports have also suggested that xAI has moved into San Francisco offices in the Mission District, a site Musk initially leased during OpenAI’s early years.

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