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SpaceX’s Starship Raptor Vacuum engine plans laid out by CEO Elon Musk
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.
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.
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.
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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Tesla CEO Elon Musk reveals new details about Robotaxi rollout
The first Tesla Robotaxi unit was spotted in Austin earlier today, and CEO Elon Musk is revealing some cool new details.
Tesla CEO Elon Musk has revealed new details about the company’s relatively imminent rollout of the Robotaxi platform as the suspected launch date of June 12 continues to near.
Earlier today, the first video showing the first driverless Tesla Robotaxi in Austin was shared on X, just a day after the City officially listed the company as an autonomous vehicle operator on its website. Tesla is listed as a company in the “Testing” phase.
🚨 BREAKING: The first Tesla Robotaxi has been spotted in Austin!
It’s has the word “Robotaxi” inscribed on the side, and it’s very clear that there is nobody in the driver’s seat.
It does appear that someone is in the passenger’s seat. https://t.co/6BdTfd4B8p pic.twitter.com/dygWCeQ5kZ
— TESLARATI (@Teslarati) June 10, 2025
The initial details of the Robotaxi are being revealed by Musk, who is carefully releasing small tidbits that seem to show the capabilities of the entire Tesla fleet, and not necessarily just the vehicles that will be involved in the initial rollout in Austin.
First Tesla driverless robotaxi spotted in the wild in Austin, TX
His first tidbit is one that many Tesla owners and fans will already know: many Teslas are capable of this driveless performance, but Full Self-Driving is not yet refined to the point where the software is quite ready to handle it. Current versions are robust, but not prepared for driverless navigation. The hardware, however, will enable Teslas to be Robotaxis, even if they’re already purchased by owners:
These are unmodified Tesla cars coming straight from the factory, meaning that every Tesla coming out of our factories is capable of unsupervised self-driving! https://t.co/n94ln0Uas6
— Elon Musk (@elonmusk) June 10, 2025
This is one of the biggest advantages Tesla has over other vehicle makers. Simply put, the Over-the-Air software updates that will roll out to FSD users will eventually make their cars into Robotaxis as well.
However, Musk shed some details on the version of FSD that is being run in these new Robotaxis that were spotted. Musk said that the version these Robotaxis are running is a new version, but will soon “merge to main branch.”
There is also an even newer version that has four times the parameters as this newer version that the test-stage Robotaxis are using, but Musk admits that this needs significant refinement before it is released to the public.
It’s a new version of software, but will merge to main branch soon.
We have a more advanced model in alpha stage that has ~4X the params, but still requires a lot of polishing.
That’s probably ready for deploy in a few months.
— Elon Musk (@elonmusk) June 10, 2025
As of now, Tesla is simply teasing the actual launch date of the Robotaxi program, but Bloomberg reported earlier this month that it will occur on June 12.
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First Tesla driverless robotaxi spotted in the wild in Austin, TX
The short clip suggests that Tesla may be ramping up its preparations for its robotaxi rollout in Austin.
A recent video posted on X has provided a first look at Tesla’s driverless robotaxi, which is expected to be deployed in Austin, Texas, this month. The vehicle was a new Tesla Model Y, which was followed by what appeared to be a manned chase car.
The short clip suggests that Tesla may be ramping up its preparations for its robotaxi rollout in Austin.
The First Robotaxi Sighting
It was evident from the short clip that the Tesla robotaxi was operating completely driverless. In the video, which was posted on X by @TerrapinTerpene, the driverless Tesla could be seen confidently making a turn. The vehicle looked and behaved like any other car on the road, save for the fact that there was no one in the driver’s seat.
Interestingly enough, the short video also provided a teaser on where Tesla will place its “robotaxi” logo on its self-driving cars. Based on the video, the robotaxis’ logo will be tastefully placed on the front doors, making the vehicles look sleek and clean.
Initial Rollout Imminent
Recent reports have suggested that Tesla is already starting the testing phase of its robotaxi service in Austin, Texas. Expectations are also high that Tesla’s initial fleet of self-driving vehicles will be utilizing a lot of teleoperation to ensure that they operate as safely as possible.
Updates to Austin’s official website recently have hinted at Tesla’s robotaxi launch. Just this Monday, Tesla was listed as an autonomous vehicle (AV) operator on Austin’s official Department of Motor Vehicles (DMV). Other AV operators listed on the site are Waymo and Zoox, among others.
Elon Musk, for his part, has noted that by the end of June, the public in Austin should be ready to take rides in Tesla robotaxis without an invitation. He also noted in late May that Tesla has been busy testing driverless cars on Austin’s city streets without any incidents.
News
Tesla Model Y proudly takes its place as China’s best-selling SUV in May
The Model Y edged out competitors like the BYD Song Plus.
The Tesla Model Y claimed its position as China’s best-selling SUV in May, with 24,770 units registered, according to insurance data from China EV DataTracker.
The Model Y edged out competitors like the BYD Song Plus, which recorded 24,240 registrations, as well as Geely’s gasoline-powered Xingyue L, which took third place with 21,014 units registered, as noted in Car News China report.
Return To The Top
The Model Y’s return to the top of China’s SUV market follows a second-place finish in April, when it trailed the BYD Song Plus by just 684 units. Tesla China had 19,984 new Model Y registrations in April, while BYD had 20,668 registrations for the Song Plus.
For the first five months of 2025, Tesla sold 126,643 Model Ys in China, outpacing the Song Plus at 110,551 units and BYD’s Song Pro at 80,245 units. This is quite impressive as the new Tesla Model Y is still a premium vehicle that is significantly more expensive than a good number of its competitors.
Year-Over-Year Challenges
Despite its SUV crown, Tesla’s year-over-year performance in China is still seeing headwinds. May sales totaled 38,588 units, a 30% year-over-year decline. From January to May, Tesla delivered 201,926 vehicles in China, a 7.8% drop year-over-year. These drops, however, are notably affected by the company’s changeover to the new Model Y in the first quarter.
Exports from Tesla’s Shanghai Gigafactory also fell, with 90,949 vehicles being shipped from January to May 2025. This represents a decline of 33.4% year-over-year, though May exports rose 33% to 23,074 units.
China’s electric vehicle market, meanwhile, showed robust growth. Total NEV sales, which includes battery electric vehicles (BEVs) and plug-in hybrids (PHEVs), reached 1,021,000 units in May, up 28% year-over-year. BEV sales alone hit 607,000 units, a 22.4% increase.
Considering the fact that China’s BEV market is extremely competitive, the Tesla Model Y’s rise to the top of the country’s SUV rankings is extremely impressive.
Tesla CEO Elon Musk reveals new details about Robotaxi rollout
First Tesla driverless robotaxi spotted in the wild in Austin, TX
Tesla Model Y proudly takes its place as China’s best-selling SUV in May
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