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SpaceX’s first orbital Starship rocket engine is almost ready for testing
CEO Elon Musk says that SpaceX is “about a month away” from testing a rocket engine that will be essential for Starship and its Super Heavy booster to reach their full potential.
Known as Raptor Vacuum, the engine – as its name suggests – is a variant of the base Raptor engine optimized for maximum performance and efficiency in the vacuum of space. Although Starship could technically still function and likely reach orbit with only sea level-optimized Raptors installed, it would likely significantly limit the amount of payload it could carry into Earth orbit and would especially harm the ship’s performance to higher orbits and other planets.
Back in May 2019, Musk revealed that SpaceX had shifted gears again, forgoing a plan to begin orbital Starship flight operations with only sea level Raptors, gradually designing and phasing in RaptorVac engines much further down the road. Instead, SpaceX restarted (relatively) urgent work on the vacuum variant and Musk hinted that it would “aspirationally” be ready to support launches in the near term. A few weeks shy of a year later, Musk says that Raptor Vacuum testing could begin as early as June 2020.
For a variety of reasons, even if based directly off of an existing design, vacuum-optimized engines are typically much more complex than a comparable sea level variant. While efficiency is always relatively important for rocket engine design, it becomes even more paramount when dealing with vacuum rocketry, as the entire point of a dedicated vacuum-optimized engine is to eke as much efficiency as possible out of a launch vehicle’s orbital stage(s).
For example, even from a purely visual perspective, Merlin Vacuum (MVac) is substantially different when compared to the Merlin 1D engine it’s based on. Due to a number of major and largely unknown differences, the engines’ shared components are largely invisible. It’s unclear how similar they are but it’s safe to say that they share at least ~50% commonality. Obviously, the most apparent part of the difference between a vacuum-optimized engine and an atmosphere-optimized engine is the bell nozzle: MVac has a nozzle that is dramatically larger than M1D.
Raptor will be no different, with the sea-level variant featuring a nozzle about 1m (3.2 ft) in diameter, whereas RaptorVac’s bell will have a diameter closer to 2.5m (~8 ft). With SpaceX’s apparent May 2019 pivot back to working on RaptorVac now, the company has been working on a dedicated vacuum variant of the high-performance methane-oxygen engine for at least a full year. Now, perhaps beginning as early as June or July, Musk suggests that the first RaptorVac engine (SN0? SN1?) is almost ready to commence static fire testing.
The nature of that testing is a bit of a mystery. While it will almost certainly occur at SpaceX’s McGregor, Texas test and development facilities, it’s unclear if Raptor Vacuum’s first static fire test campaign will be attempted with the engine’s extended nozzle installed. Back in October 2019, Musk suggested that yes, Raptor Vacuum version 1.0 would have a nozzle small enough to operate at sea level without destroying itself or its test facilities. With Merlin Vacuum engines, SpaceX performs acceptance tests in Texas but only without their nozzle extensions installed. If Musk’s October 2019 comments remain true, that may not be the case for RaptorVac.
Either way, it will be thoroughly interesting to note the differences between RaptorVac and its sea level-optimized predecessor if or when Elon Musk or SpaceX releases photos of their newest engine as it nears its first major tests. Simultaneously, SpaceX is also readying a sea-level Raptor for its inaugural static fire test while attached to a full-scale Starship prototype, while the first test with three Raptor engines installed could be attempted just a few weeks from now.
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News
Elon Musk makes a key Tesla Optimus detail official
“Since we are naming the singular, we will also name the plural, so Optimi it is,” Musk wrote on X.
Tesla CEO Elon Musk just made a key detail about Optimus official. In a post on X, the CEO clarified some key wording about Optimus, which should help the media and the public become more familiar with the humanoid robot.
Elon Musk makes Optimus’ plural term official
Elon Musk posted a number of Optimus-related posts on X this weekend. On Saturday, he stated that Optimus would be the Von Neumann probe, a machine that could eventually be capable of replicating itself. This capability, it seems, would be the key to Tesla achieving Elon Musk’s ambitious Optimus production targets.
Amidst the conversations about Optimus on X, a user of the social media platform asked the CEO what the plural term for the humanoid robot will be. As per Musk, Tesla will be setting the plural term for Optimus since the company also decided on the robot’s singular term. “Since we are naming the singular, we will also name the plural, so Optimi it is,” Musk wrote in his reply on X.
This makes it official. For media outlets such as Teslarati, numerous Optimus bots are now called Optimi. It rolls off the tongue pretty well, too.
Optimi will be a common sight worldwide
While Musk’s comment may seem pretty mundane to some, it is actually very important. Optimus is intended to be Tesla’s highest volume product, with the CEO estimating that the humanoid robot could eventually see annual production rates in the hundreds of millions, perhaps even more. Since Optimi will be a very common sight worldwide, it is good that people can now get used to terms describing the humanoid robot.
-->During the Tesla 2025 Annual Shareholder Meeting, Musk stated that the humanoid robot will see “the fastest production ramp of any product of any large complex manufactured product ever,” starting with a one-million-Optimi-per-year production line at the Fremont Factory. Giga Texas would get an even bigger Optimus production line, which should be capable of producing tens of millions of Optimi per year.
News
Tesla is improving Giga Berlin’s free “Giga Train” service for employees
With this initiative, Tesla aims to boost the number of Gigafactory Berlin employees commuting by rail while keeping the shuttle free for all riders.
Tesla will expand its factory shuttle service in Germany beginning January 4, adding direct rail trips from Berlin Ostbahnhof to Giga Berlin-Brandenburg in Grünheide.
With this initiative, Tesla aims to boost the number of Gigafactory Berlin employees commuting by rail while keeping the shuttle free for all riders.
New shuttle route
As noted in a report from rbb24, the updated service, which will start January 4, will run between the Berlin Ostbahnhof East Station and the Erkner Station at the Gigafactory Berlin complex. Tesla stated that the timetable mirrors shift changes for the facility’s employees, and similar to before, the service will be completely free. The train will offer six direct trips per day as well.
“The service includes six daily trips, which also cover our shift times. The trains will run between Berlin Ostbahnhof (with a stop at Ostkreuz) and Erkner station to the Gigafactory,” Tesla Germany stated.
Even with construction continuing at Fangschleuse and Köpenick stations, the company said the route has been optimized to maintain a predictable 35-minute travel time. The update follows earlier phases of Tesla’s “Giga Train” program, which initially connected Erkner to the factory grounds before expanding to Berlin-Lichtenberg.
-->Tesla pushes for majority rail commuting
Tesla began production at Grünheide in March 2022, and the factory’s workforce has since grown to around 11,500 employees, with an estimated 60% commuting from Berlin. The facility produces the Model Y, Tesla’s best-selling vehicle, for both Germany and other territories.
The company has repeatedly emphasized its goal of having more than half its staff use public transportation rather than cars, positioning the shuttle as a key part of that initiative. In keeping with the factory’s sustainability focus, Tesla continues to allow even non-employees to ride the shuttle free of charge, making it a broader mobility option for the area.
News
Tesla Model 3 and Model Y dominate China’s real-world efficiency tests
The Tesla Model 3 posted 20.8 kWh/100 km while the Model Y followed closely at 21.8 kWh/100 km.
Tesla’s Model 3 and Model Y once again led the field in a new real-world energy-consumption test conducted by China’s Autohome, outperforming numerous rival electric vehicles in controlled conditions.
The results, which placed both Teslas in the top two spots, prompted Xiaomi CEO Lei Jun to acknowledge Tesla’s efficiency advantage while noting that his company’s vehicles will continue refining its own models to close the gap.
Tesla secures top efficiency results
Autohome’s evaluation placed all vehicles under identical conditions, such as a full 375-kg load, cabin temperature fixed at 24°C on automatic climate control, and a steady cruising speed of 120 km/h. In this environment, the Tesla Model 3 posted 20.8 kWh/100 km while the Model Y followed closely at 21.8 kWh/100 km, as noted in a Sina News report.
These figures positioned Tesla’s vehicles firmly at the top of the ranking and highlighted their continued leadership in long-range efficiency. The test also highlighted how drivetrain optimization, software management, and aerodynamic profiles remain key differentiators in high-speed, cold-weather scenarios where many electric cars struggle to maintain low consumption.
Xiaomi’s Lei Jun pledges to continue learning from Tesla
Following the results, Xiaomi CEO Lei Jun noted that the Xiaomi SU7 actually performed well overall but naturally consumed more energy due to its larger C-segment footprint and higher specification. He reiterated that factors such as size and weight contributed to the difference in real-world consumption compared to Tesla. Still, the executive noted that Xiaomi will continue to learn from the veteran EV maker.
“The Xiaomi SU7’s energy consumption performance is also very good; you can take a closer look. The fact that its test results are weaker than Tesla’s is partly due to objective reasons: the Xiaomi SU7 is a C-segment car, larger and with higher specifications, making it heavier and naturally increasing energy consumption. Of course, we will continue to learn from Tesla and further optimize its energy consumption performance!” Lei Jun wrote in a post on Weibo.
-->Lei Jun has repeatedly described Tesla as the global benchmark for EV efficiency, previously stating that Xiaomi may require three to five years to match its leadership. He has also been very supportive of FSD, even testing the system in the United States.
Elon Musk makes a key Tesla Optimus detail official
Tesla is improving Giga Berlin’s free “Giga Train” service for employees
