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SpaceX sends “radically redesigned” Starship engine to Texas for hot-fire tests

As of September 2017, subscale Raptor engines had been cumulatively fired for more than 1200 seconds in just 12 months of testing. (SpaceX)

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SpaceX has shipped one of the first of a group of Starship engines known as Raptor, described last month by CEO Elon Musk as “radically redesigned”. A culmination of more than 24 months of prototype testing, the first flight-worthy Raptor could be ignited for the first time as early as February.

According to Musk, three of these redesigned Raptors will power the first full-scale BFR prototype, a Starship (upper stage) test article meant to conduct relatively low-altitude, low-velocity hop tests over the southern tip of Texas. Those tests could also begin next month, although a debut sometime in March or April is increasingly likely.

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Effectively designed on a blank slate, Raptor began full-scale component-level tests in 2014 at NASA’s Mississippi-based Stennis Space Center, evolving from main injector development to oxygen preburner hot-fires in 2015. Soon after Raptor’s prototype preburner design was validated at Stennis, SpaceX moved testing to its privately-owned and operated facilities in McGregor, Texas, where Raptor static fire testing has remained since.

Just days before CEO Elon Musk was scheduled to reveal SpaceX’s next-generation rocket (BFR, formerly known as the Interplanetary Transport System or ITS) in September 2016, he announced in a tweet that propulsion engineers and technicians had successful hot-fired an integrated Raptor prototype – albeit subscale – for the first time ever. Just 12 months later, Musk once again took to the stage to announce an update to BFR’s design, while also revealing that prototype Raptor engines had already completed more than 1200 seconds (20 minutes) of cumulative hot-fire tests, an extremely aggressive and encouraging rate of progress for such a new engine.

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Although Raptor undoubtedly borrows heavily from much of the same expertise that designed Merlin 1 and operated and improved it for years, that is roughly where the similarities between Raptor and M1D end. M1D, powered by refined kerosene (RP-1) and liquid oxygen, uses a combustion cycle (gas-generator) that is relatively simple and reliable at the cost of engine efficiency, although SpaceX propulsion expertise still managed to give M1D the highest thrust-to-weight ratio of any liquid rocket engine ever flown. Still, measured by ISP (instantaneous specific impulse), M1D’s inefficient kerolox gas-generator cycle ultimately means that the engine simply can’t compete with the performance of engines with more efficient propellants and combustion cycles.

While SpaceX’s Falcon 9 and Heavy rockets – powered by Merlin 1D and Merlin Vacuum – are more than adequate in and around Earth orbit, a far more efficient engine was needed for the company to enable the sort of interplanetary colonization Musk had in mind when he created SpaceX. Raptor was the answer. Ultimately settling on liquid methane and oxygen (methalox) as the propellant and a full-flow staged-combustion (FFSC) cycle, Raptor was designed to be extraordinarily reliable and efficient in order to safely power a spacecraft (BFS/Starship) meant to ferry dozens or hundreds of people to and from Mars.

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An excellent NASASpaceflight article explores the engine’s journey from a blank sheet to integrated static-fire tests and offers a deeper explanation of the technical details.

Raptor enters a new era

For all the extensive and invaluable testing SpaceX has done with a series of prototype Raptor engines, the engines tested were subscale versions with around 30% the thrust of the c. 2016 Raptor and around 40-50% of the updated c. 2017 iteration, producing almost the same amount of thrust as Merlin 1D (914 kN to Raptor’s ~1000 kN). In September 2018, Musk described Raptor as an “approximately…200-ton (~2000 kN) thrust engine” that would eventually operate with a chamber pressure as high as 300 bar (an extraordinary ~4400 psi), requiring at least one of the FFSC engine’s two preburners (used to power separate turbopumps) to operate at a truly terrifying ~810 bar (nearly 12,000 psi).

Conveniently stood beside a Merlin 1D engine also ready for hot-fire acceptance testing, the Raptor engine spotted departing SpaceX’s Hawthorne, CA factory last week was reportedly immense in person, towering over an M1D engine. Raptor also featured a mass of spaghetti-like plumbing (complexity necessary for its advanced combustion cycle), with a significant fraction of the metallic pipes and tubes displaying mirror-like finishes. Most notable was an obvious secondary preburner/turbopump stack and the lack of any exhaust port, whereas M1D relies on a single turbopump and exhausts the gases used to power it. Raptor’s full-flow staged-combustion cycle uses separate oxygen and methane preburners to power separate turbopumps, significantly improving mass flow rate and smoothing out combustion mixing.

 

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Unlike all previous hot-fired Raptors, those shipping now to McGregor, Texas are expected to be the first completed engines with a finalized design, arrived at only after a period of extensive testing and iterative improvement. They also appear to be full-scale, meaning that the test bays dedicated to Raptor will likely need to be upgraded (if they haven’t been already) to support a two- or threefold increase in maximum thrust.

SpaceX’s Starship hopper will need three finalized engines, meaning that the Raptor now in McGregor, Texas may not have been the first to arrive. Nevertheless, the shipment of full-scale hardware is always an extremely encouraging milestone for any advanced technology development program, while also foreshadowing the first imminent static-fires of the “radcally redesigned” rocket engine. With hardware now at the test site before January is out, a February test debut – one month behind a January debut teased by Elon Musk last December – is not out of the question.

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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 Cybercab display highlights interior wizardry in the small two-seater

Photos and videos of the production Cybercab were shared in posts on social media platform X.

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Credit: Tesla Robotaxi/X

The Tesla Cybercab is currently on display at the U.S. Department of Transportation in Washington, D.C., and observations of the production vehicle are highlighting some of its notable design details. 

Photos and videos of the production Cybercab were shared in posts on social media platform X.

Observers of the Cybercab display unit noted that the two-seat Robotaxi provides unusually generous legroom for a vehicle of its size. Based on the vehicle’s video, the compact two-seater appears to offer more legroom than Tesla’s larger vehicles such as the Model Y, Model X, and Cybertruck.

The Cybercab’s layout allows Tesla to dedicate nearly the entire cabin to passengers. The vehicle is designed without a steering wheel or pedals, which helps maximize interior space.

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Footage from the display also highlights the Cybercab’s large center screen, which is positioned prominently in front of the passenger bench. The display appears intended to provide entertainment and ride information while the vehicle operates autonomously.

Images of the vehicle also show an additional camera integrated into the Cybercab’s C-pillar. The extra camera appears to expand the vehicle’s field of view, which would be useful as Tesla works toward fully unsupervised Full Self-Driving.

Tesla engineers have previously explained that the Cybercab was designed to be highly efficient both in manufacturing and in operation. Cybercab Lead Engineer Eric E. stated in 2024 that the Robotaxi would be built with roughly half the number of parts used in a Model 3 sedan.

“Two seats unlocks a lot of opportunity aerodynamically. It also means we cut the part count of Cybercab down by a substantial margin. We’re gonna be delivering a car that has roughly half the parts of Model 3 today,” the Tesla engineer said.

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The Tesla engineer also noted that the Cybercab’s cargo area can accommodate multiple golf bags, two carry-on suitcases, and two full-size checked bags. The trunk can also fit certain bicycles and a foldable wheelchair depending on size, which is quite impressive for a small car like the Cybercab.

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Elon Musk’s xAI wins permit for power plant supporting AI data centers

The development was reported by CNBC, citing confirmation from the Mississippi Department of Environmental Quality (MDEQ).

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Mississippi regulators have approved a permit allowing Elon Musk’s artificial intelligence company xAI to construct a natural gas power plant in Southaven. The facility is expected to support the company’s expanding AI infrastructure tied to its Colossus data center operations near Memphis.

The development was reported by CNBC, citing confirmation from the Mississippi Department of Environmental Quality (MDEQ).

According to the report, regulators “voted to approve the permit” of xAI subsidiary MZX Tech LLC to construct a power plant featuring 41 natural gas-burning turbines “after careful consideration of all public comments and community concerns.”

The Mississippi Department of Environmental Quality stated that the permit followed a regulatory review process that included public comments and community input. Jaricus Whitlock, air division chief for the MDEQ, stated that the project met all applicable environmental standards.

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“The proposed PSD permit in front of the board today not only meets all state and federal permitting regulations, but goes above and beyond what is required by law. MDEQ and the EPA agree that not a single person around our facilities will be exposed to unhealthy levels of air pollution,” Whitlock stated.

The planned facility will help provide electricity for xAI’s AI computing infrastructure in the Memphis region.

The Southaven project forms part of xAI’s efforts to scale computing capacity for its artificial intelligence systems.

The company currently operates two major data centers in Memphis, known as Colossus 1 and Colossus 2, which provide computing power for xAI’s Grok AI models. xAI is also planning to build another large data center in Southaven called Macrohardrr, which would be located in a warehouse previously used by GXO Logistics.

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Large-scale AI training requires substantial computing power and electricity, prompting technology companies to develop dedicated energy infrastructure for their data centers.

SpaceX President Gwynne Shotwell previously stated that xAI plans to develop 1.2 gigawatts of power capacity for its Memphis-area AI supercomputer site as part of the federal government’s Ratepayer Protection Pledge. The commitment was announced during an event with United States President Donald Trump.

“As part of today’s commitment, we will take extensive additional steps to continue to reduce the costs of electricity for our neighbors. xAI will therefore commit to develop 1.2 GW of power as our supercomputer’s primary power source. That will be for every additional data center as well. We will expand what is already the largest global Megapack power installation in the world,” Shotwell said.

“The installation will provide enough backup power to power the city of Memphis, and more than sufficient energy to power the town of Southaven, Mississippi where the data center resides. We will build new substations and invest in electrical infrastructure to provide stability to the area’s grid.”

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Tesla China teases Optimus robot’s human-looking next-gen hands

The image was shared by Tesla AI’s account on Weibo and later reposted by Tesla community members on X.

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Credit: Tesla China

A new teaser shared by Tesla’s China team appears to show a pair of unusually human-like hands for Optimus. 

The image was shared by Tesla AI’s account on Weibo and later reposted by Tesla community members on X.

As could be seen in the teaser image, the new version of Optimus’ hands features proportions and finger structures that look strikingly similar to those of a human hand. Their appearance suggests that they might have dexterity approaching that of a human hand.

If the image reflects a new generation of Optimus’ hands, it could indicate Tesla is continuing to refine one of the most critical components of its humanoid robot.

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Hands are widely viewed as one of the most difficult engineering challenges in robotics. For Optimus to perform complex real-world work, from manufacturing tasks to household activities, its hands would need to be the best in the industry.

Elon Musk has repeatedly described Optimus as Tesla’s most important long-term product. In posts on social media platform X, Musk has stated that Optimus could eventually become the first real-world Von Neumann machine.

In theory, a Von Neumann machine is a self-replicating system capable of building copies of itself using available materials. The concept was originally proposed by mathematician John von Neumann in the mid-20th century.

“Optimus will be the first Von Neumann machine, capable of building civilization by itself on any viable planet,” Musk wrote in a post on X.

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If Optimus is expected to carry out complex work autonomously in the future, high levels of dexterity will likely be essential. This makes the development of advanced robotic hands a key step towards Musk’s long-term expectations for the product.

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