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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.

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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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Musk forces Judge’s exit from shareholder battles over viral social media slip-up

McCormick insisted in a court filing that she harbors no actual bias against Musk or the defendants. She claimed she either never clicked the “support” button, LinkedIn’s version of a “like,” or did so accidentally.

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(Credit: Tesla)

Many Tesla fans are familiar with the name Kathaleen McCormick, especially if they are investors in the company.

McCormick is a Delaware Chancery Court Judge who presided over Tesla CEO Elon Musk’s pay package lawsuit over the past few years, as well as his purchase of Twitter. However, she will no longer be sitting in on any issues related to Musk.

Elon Musk demands Delaware Judge recuse herself after ‘support’ post celebrating $2B court loss

In a rare admission of potential optics issues in one of America’s most powerful corporate courts, Delaware Chancery Court Chancellor Kathaleen McCormick stepped aside Monday from a cluster of shareholder lawsuits targeting Elon Musk and Tesla’s board.

The move came just days after Musk’s legal team highlighted her apparent “support” on LinkedIn for a post that mocked the billionaire over his 2022 tweets about the $44 billion Twitter acquisition.

McCormick insisted in a court filing that she harbors no actual bias against Musk or the defendants. She claimed she either never clicked the “support” button, LinkedIn’s version of a “like,” or did so accidentally.

She wrote in a newly published memo from the Delaware Chancery Court:

“The motion for recusal rests on a false premise — that I support a LinkedIn post about Mr. Musk, which I do not in fact support. I am not biased against the defendants in these actions.”

Yet she granted the reassignment anyway, acknowledging that the intense media scrutiny surrounding her involvement had become “detrimental to the administration of justice.”

The consolidated cases will now be handled by three of her colleagues on the Delaware Court of Chancery, the nation’s go-to venue for high-stakes corporate disputes. The lawsuits accuse Musk and Tesla directors of breaching fiduciary duties through lavish executive compensation and lax governance oversight.

One prominent claim, filed by a Detroit pension fund, challenges massive stock awards granted to board members, alleging the payouts harmed the company. The litigation also overlaps with issues stemming from Musk’s turbulent 2022 Twitter purchase.

McCormick’s history with Musk made her a lightning rod. In 2022, she presided over the fast-tracked lawsuit that ultimately forced Musk to complete the Twitter deal after he tried to back out.

Then in 2024, she struck down his record $56 billion Tesla compensation package, ruling the approval process was flawed and overly CEO-friendly. The Delaware Supreme Court later reinstated the pay on technical grounds, but the ruling fueled Musk’s long-standing criticism of the state’s judiciary.

Musk has repeatedly urged companies to reincorporate elsewhere, arguing Delaware courts have grown hostile to visionary leaders. Monday’s recusal hands him a symbolic victory and underscores how personal social-media activity can collide with judicial impartiality standards.

Delaware law requires judges to step aside if there’s even a “reasonable basis” to question their neutrality.

Court watchers say the episode highlights growing tensions in corporate America’s legal epicenter. While McCormick maintained her impartiality, the appearance of bias proved too costly to ignore. The cases will proceed without her, but the broader debate over Delaware’s dominance in business litigation is far from over.

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Elon Musk has generous TSA offer denied by the White House: here’s why

Musk stepped in on March 21 via a post on X, writing: “I would like to offer to pay the salaries of TSA personnel during this funding impasse that is negatively affecting the lives of so many Americans at airports throughout the country.”

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Gage Skidmore, CC BY-SA 4.0 , via Wikimedia Commons

Tesla and SpaceX CEO Elon Musk made a generous offer to pay the salaries of Transportation Security Administration (TSA) employees last week, but the offer was denied by the White House.

In a striking display of private-sector initiative clashing with federal bureaucracy, the White House has turned down an offer from Elon Musk to personally cover the salaries of TSA officers amid an ongoing partial government shutdown. The rejection, reported last Wednesday by multiple outlets, highlights the legal and political hurdles facing unconventional solutions to Washington’s funding gridlock.

The impasse began weeks ago when Congress failed to pass funding for the Department of Homeland Security (DHS), leaving TSA employees, essential workers who screen millions of travelers daily, without paychecks while still required to report for duty.

Frustrated travelers have endured record-long security lines at major airports, with reports of chaos and delays rippling across the country.

Musk stepped in on March 21 via a post on X, writing: “I would like to offer to pay the salaries of TSA personnel during this funding impasse that is negatively affecting the lives of so many Americans at airports throughout the country.”

But it was not for no reason.

White House spokesperson Abigail Jackson responded on behalf of the Trump administration, expressing appreciation for Musk’s gesture.

However, the legal obstacles, which would be insurmountable, would inhibit Musk from doing so. Jackson said:

“We greatly appreciate Elon’s generous offer. This would pose great legal challenges due to his involvement with federal government contracts.”

Musk’s companies hold significant federal contracts, including NASA launches through SpaceX and potential Defense Department work, raising concerns about conflicts of interest, ethics rules, and anti-bribery statutes that prohibit private payments to government employees. Administration officials also indicated they expect the shutdown to end soon, making external funding unnecessary.

The episode underscores deeper tensions in Washington. Musk, who has advised on government efficiency efforts and maintains a close relationship with President Trump, has frequently criticized wasteful spending and bureaucratic delays.

His offer came as airport security lines ballooned, drawing public frustration toward both parties. TSA officers, many of whom rely on paychecks to cover mortgages and family expenses, have continued working without compensation, a situation that has drawn bipartisan concern but little immediate resolution.

Critics of the rejection argue it prioritizes red tape over practical relief for frontline workers and travelers. Supporters of the White House position counter that allowing private funding sets a dangerous precedent and could undermine congressional authority over the budget.

The White House eventually came to terms with the TSA on Friday and started paying them once again, and lines at airports instantly shrank.  The Department of Homeland Security (DHS) said that TSA staf would begin receiving paychecks “as early as” today.

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Tesla FSD mocks BMW human driver: Saves pedestrian from near miss

Tesla FSD anticipated a BMW driver’s lane drift before the human behind the wheel could react.

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A video posted to r/TeslaFSD this week put a sharp spotlight on Tesla’s Full Self-Driving (FSD) software being able to react to pedestrian intent than an actual human driver behind the wheel. In the Reddit clip, a BMW driver can be seen rolling through a neighborhood street completely unaware of a pedestrian stepping in to cross. At the same time, a Tesla  driving on FSD had already begun slowing down before the pedestrian even began their attempt to cross the street The BMW kept moving, prompting the pedestrian to hop back, while the Tesla came to a stop and provide right-of-way for the human to safely cross.

That gap between what the BMW driver saw and what FSD had already processed is the story. Tesla FSD wasn’t reacting to a person in the street, rather it was reading the signals that a person was about to enter it based on the pedestrian’s movement, trajectory, and their trajectory to telegraph intent.

Tesla’s FSD is now built on an end-to-end neural network trained on billions of real-world miles, learning to interpret subtle human behavioral cues the same way an experienced human driver does instinctively. The difference is consistency. A human driver distracted for two seconds misses what FSD does not.

Tesla sues California DMV over Autopilot and FSD advertising ruling

Reddit commenters in the thread were blunt about the BMW driver’s failure, with several pointing out that the pedestrian was visible well before the crossing. One response put it plainly that the car on FSD saw the situation developing before the human in the other car had registered there was a situation at all.

Tesla has published data showing FSD (Supervised) is 54% safer than a human driver, accumulated across billions of miles driven on the system. Elon Musk has said FSD v14 will outperform human drivers by a factor of two to three, and that v15 has “a shot” at a 10x improvement. Pedestrian safety is where the stakes are highest, and where intent prediction closes the gap fastest. At 30 mph, a car covers roughly 44 feet per second. An extra second of awareness from reading a person’s body language rather than waiting for them to step out is often the difference between a near miss and a fatality.

Video and community discussion: r/TeslaFSD on Reddit

FSD saves man from becoming a pancake. BMW driver nearly flattens him.
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