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SpaceX's "Christmas tree" is a Raptor engine for the holidays

Raptor performs a static fire test at SpaceX's McGregor, Texas development facilities. (SpaceX)

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SpaceX CEO Elon Musk showed off a holiday-themed Raptor engine “Christmas tree” with its very own star on top. Musk noted via a tweet that the company’s Starship propulsion team is “making great progress” building, testing, and refining the Raptor engines that will one day propel the next-generation rocket to Earth orbit and beyond.

On December 13th, Musk revealed that SpaceX is preparing to ship the 17th completed Raptor engine to the company’s McGregor, Texas rocket test and development facilities, the site of several dedicated test stands for the Starship engine. Likely one of the most complex rocket engines ever designed, built, or tested, Raptor relies on an exotic combustion cycle, referring to the specifics of how engines turn their propellant into meaningful thrust.

Raptor uses what is known as full-flow staged combustion (FFSC) and is the first FFSC engine to graduate beyond ground testing and actually fly, thus far having completed two flight tests in July and August 2019 as part of SpaceX’s Starhopper test campaign. In simple terms, the FFSC cycle aims to extract as much energy from a rocket’s propellant as efficiently as possible, resulting in what is theoretically the most efficient possible chemical propulsion from a given fuel and oxidizer combination.

Due to the sheer complexity required to achieve full-flow staged combustion, the engine type is incredibly rare and only two other (once) functional examples exist – one developed by Soviet engineers in the 20th century and the other built, tested, and inexplicably scrapped by NASA in the 2000s. In fact, the Soviet RD-270 engine’s thrust-to-weight ratio is likely second only to SpaceX’s own Merlin 1D engine, an absolutely spectacular achievement for a propulsion bureau operating in the late 1960s.

RD-270 had major development challenges and would likely have taken years of additional hardware-rich (i.e. destructive trial and error) testing to produce an engine actually capable of reliable flight. Before the program was cancelled in 1970, 22 engines were tested and no single RD-270 survived to perform a fourth static fire, a testament to the immense challenge of FFSC engines.

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Energomash’s FFSC RD-270 engine.

SpaceX appears to have had a much better go of it with Raptor, although many, many engines have definitely been destroyed or irreparably damaged since the full-scale engine’s February 2019 static fire debut. SpaceX CEO Elon Musk says that the 17th completed Raptor engine is almost ready to head to McGregor, Texas to kick off development and acceptance testing.

It remains to be seen when exactly Raptor engines will be mature and reliable enough to perform the 3-10 minute burns needed to send a Starship to orbit, let alone the Moon or Mars, but Musk appears confident that SpaceX is making great progress along those lines.

Per photos and info posted by NASASpaceflight.com earlier today, Raptor engine SN15 is already installed on a recently-reactivated McGregor test stand ahead of its first rocket-related test in almost half a decade.

Formerly used to test Falcon 9 first stages before SpaceX built a new stand for Falcon 9 and Heavy, that tripod stand has been reactivated for the sole purpose of supporting vertical Raptor engine static fire testing, which Musk says will simplify and expedite development by making test conditions much more flight-like. As of now, all subscale and full-scale Raptor engine static fire testing has been performed at horizontal test stands in McGregor, apparently resulting in wear and behavior that would not likely appear if engines were tested vertically.

SpaceX has gone through the same process with its Merlin engine programs, beginning with horizontal testing (far easier and simpler) but ultimately building a number of dedicated vertical test bays to ensure that engine acceptance and development tests can be performed under more flight-like conditions.

SpaceX’s Merlin 1D (Vacuum and Sea Level) tests stands, as well as a bay for upper stage static fires. (April 17, 2018 – Aero Photo)

According to NASASpaceflight, SpaceX may have already fired up Raptor SN15 on its reactivated tripod test stand earlier this week, kicking off Raptor’s first Starhopper-free vertical static fire testing. It’s now unclear where the twin horizontal Raptor test bays will fit into future engine testing given Musk’s comments. More importantly, every completed Starship and Super Heavy rocket will require several dozen new Raptor engines and every one of those engines will likely need to pass acceptance testing (including static fires) in McGregor before they can be installed on a launch vehicle.

SpaceX’s Falcon 9 rocket already requires 10 engines per new booster and upper stage, a test burden SpaceX has only managed with the help of two Merlin 1D stands and one Merlin Vacuum stand, all vertical. In other words, it’s safe to say that the reactivated tripod stand is likely just the first of several vertical Raptor test stands to come.

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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 Robotaxis are becoming a common sight on Austin’s public roads

Tesla Robotaxi sightings are becoming much more frequent ahead of its launch planned for this month.

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Credit: @Muzeishen | X

Tesla Robotaxis are becoming a common sight on the public roads of Austin, Texas, as yet another test mule has been spotted near the company’s target launch date.

Just over a week ago, the first public sighting of a driverless Tesla Robotaxi was reported. The vehicle was an updated version of the Tesla Model Y, which will be the initial model used in the public deployment of the Robotaxi platform.

Throughout the past week, sightings have been more common, as people in Austin have been looking for the unique decal Tesla is placing on car doors to recognize the driverless vehicles (After all, Robotaxis are not as easy to recognize as driverless vehicles without the LIDAR unit on the roof like Waymo).

Yet another sighting of a Robotaxi was shared on social media today, just two days before CEO Elon Musk’s proposed launch date of June 22:

It is easy to tell that there is nobody in the driver’s seat of this vehicle. Tesla is using its white interior on this particular mule, making it incredibly simple to recognize that no human is controlling the car.

Whether Tesla will still meet the June 22nd deadline remains to be seen, but it is no secret that the company is prioritizing safety ahead of offering public rides.

Tesla will initially roll out the Robotaxi platform in Austin, but it has already started the regulatory process in other areas, specifically California.

The National Highway Traffic Safety Administration (NHTSA) is also helping to streamline the process for companies developing driverless vehicles by giving exemptions to automakers. It will make things much more efficient, benefiting Tesla and other car companies that have similar plans.

Tesla Robotaxi just got a big benefit from the U.S. government

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Elon Musk teases Tesla Optimus Gen 3 capabilities: ‘So many improvements’

If you thought Optimus Gen 2 was impressive, Tesla might have a surprise for you.

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Credit: Tesla Optimus | X

Elon Musk has teased that huge improvements are coming to Tesla’s Optimus humanoid robot, which is arguably the product that the company is developing with the most potential for everyday use by consumers and valuation increases from a financial perspective.

Optimus is still in the development stages, but Tesla has made great strides in its development over the past several years. It started as a simple idea that was unveiled with a human being in a spandex suit.

Tesla posts Optimus’ most impressive video demonstration yet

Just a few years later, Tesla has developed several humanoid robot prototypes that have made their way to influencers and have lent a helping hand around the company’s manufacturing facilities.

Tesla has already introduced two generations of Optimus, as the most recent release featured a vast number of improvements from the initial version.

The following is a list of things Tesla improved upon with Optimus Gen 2 compared to Gen 1:

  • Tesla introduced a weight reduction of roughly 22 pounds, improving efficiency and agility
  • Optimus Gen 2 had a walking speed that improved by 30 percent over Gen 1
  • Tesla developed more capable hands that had 22 degrees of freedom, double that of Gen 1. This improved object handling
  • Optimus Gen 2 had a 2-degree-of-freedom neck, as Gen 1’s was fixed
  • Tesla integrated actuators and sensors for better performance. This includes things like foot force/torque sensing, articulated toe sections that are close to human foot geometry for better balance and movement
  • Optimus Gen 2 has 28 degrees of overall freedom, improving flexibility from the first generation
  • Tesla’s Optimus Gen 2 can do more than Gen 1, and has shown improved motor control and precision, doing things like squats, yoga poses, dancing, and even poaching an egg

These changes essentially brought Tesla closer to what will be the Optimus version that makes it to production. The company has plans to start production for the public in 2026, but some units will be manufactured for internal use within its factories as soon as this year. Tesla has said it could scale to 100,000 units or more by next year.

Musk also revealed to Teslarati recently that the company is in the process of building the production line that will bring manufacturing rates of Optimus to that level.

However, there is another design of Optimus coming, and Musk says it will feature “so many improvements”:

Tesla has said that Optimus will have the capability to perform tedious and time-consuming tasks like folding laundry, babysitting, cooking, walking the dog, and plenty of other things. However, it will be super impressive to see it do things that require true coordination, like threading a needle, for example.

Musk did not hint toward any specific developments that Tesla will aim for with Optimus Gen 3, but the sky is the limit, especially as it will be performing some manufacturing tasks across its factories.

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Elon Musk

Elon Musk slams Bloomberg’s shocking xAI cash burn claims

Musk stated that “Bloomberg is talking nonsense.”

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Credit: xAI/X

Elon Musk has forcefully rejected Bloomberg News’ claims that his artificial intelligence startup, xAI, is hemorrhaging $1 billion monthly. 

In a post on X, Musk stated that “Bloomberg is talking nonsense.” He also acknowledged an X user’s comment that people “really have no idea what’s at stake” with AI.

Bloomberg‘s Allegations and Musk’s Rebuttal

The Bloomberg News report painted a dire picture of xAI’s finances. Citing people reportedly familiar with the matter, the news outlet claimed that xAI burns $1 billion a month as costs for building advanced AI models outpaced the company’s limited revenues. 

Bloomberg alleged that xAI is planning to spend over half of a proposed $9.3 billion fundraising haul in three months, with a projected $13 billion loss in 2025. The report also claimed that of the $14 billion that xAI has raised since 2023, only $4 billion remained by Q1 2025. Even this amount, the news outlet alleged, will be nearly depleted in Q2.

xAI did not comment on Bloomberg‘s claims, though Elon Musk shared his thoughts on the matter on social media platform X. In response to an X user who quoted the publication’s article, Musk noted that “Bloomberg is talking nonsense.” Musk, however, did not provide further details as to why the publication’s report was fallacious.

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xAI’s Bright Horizon

Despite Bloomberg‘s claims, even the publication noted that xAI’s prospects are promising. The company, now merged with X, aims to leverage the platform’s vast data archives for model training, which could reduce costs compared to rivals like OpenAI. Tapping into X also allows xAI to access real-time information from users across the globe. 

xAI’s valuation reportedly soared to $80 billion by Q1 2025, up from $51 billion in 2024. The AI startup has attracted heavyweight investors such as Andreessen Horowitz, Sequoia Capital, and VY Capital so far, and optimistic projections point to profitability possibly being attained by 2027. This would be quite a feat for xAI as OpenAI, the AI startup’s biggest rival, is still looking at 2029 as the year it could become cash flow positive.

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