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SpaceX to use superalloys in Mars rocket Raptor engines, says Elon Musk
A few days after he touched upon methods of creating BFR propellant on Mars, SpaceX CEO Elon Musk mentioned in a tweet that the launch company was using cutting-edge combinations of metals (known as superalloys) to ensure the efficiency and reliability of its Raptor rocket engine, a critical requirement for BFR to enable sustainable colonization of Mars.
In response to a tweeted question about types of metal alloys currently in use at SpaceX, Musk briefly delved into the complexities of building BFR’s propulsion system, particularly with respect to alloys capable of surviving the intense conditions inside a rocket engine:
“[SpaceX is using] SX 300 & soon SX 500. Kind of a modern version of Inconel superalloys. High strength at temperature, extreme oxidation resistance. Needed for ~800 atmosphere, hot, oxygen-rich turbopump on Raptor rocket engine.” – Elon Musk
There’s a lot to break down for the layperson in Musk’s tweet. First and foremost, commenters (your author included) immediately jumped to the conclusion that “SX 300/500” referred to some sort custom SpaceX material, given that SX is a frequent shorthand for SpaceX used in the enthusiast community. In reality, it was quickly discovered that the requirements Musk described for the material – namely “high strength at temperature [&] extreme oxidation resistance” – were nearly the exact same qualities of single-crystal superalloys, extremely advanced metal formulations also notated as SC or SX. It’s quite the apt coincidence that SpaceX will apparently rely on SX alloys for critical components of BFR propulsion.
A 2017 test-firing of the mature development Raptor, roughly 50% less powerful than the full-scale system. (SpaceX)
Single-crystal superalloys employ small amounts of exotic elements in order to better ensure truly unusual crystal formation in metal structures. In the case of SX alloys, the optimal result is a monolithic metal structure that effectively has no visible grain (think wood grain but in metal) – the resulting metal would be a huge monolithic crystal, in other words, uniform down to a near-atomic level. These SX superalloys are already used regularly for industrial applications requiring the ability to reliably operate in extremely corrosive high-pressure, high-temperature environments for long periods of time, most frequently seen in gas turbines for energy generation and airplane propulsion.
Per Musk, SpaceX intends to take those alloys a step further, developing its own SX-300 and SX-500 iterations for the purpose of building a reliable, robust turbopump for the Raptor propulsion system. In pursuit of the greatest possible efficiency, Raptor’s turbopump will run oxygen-rich, meaning that the inherently imperfect combustion process will lean towards excess oxygen in the exhaust, rather than excess methane. In simple terms, this choice is partially motivated by the fact that oxygen molecules are slightly lighter than methane molecules (15.999u vs. 16.04u). More importantly, the higher the pressure in the turbopump, the higher the pressure in Raptor’s combustion chamber, which directly correlates with more efficient combustion and thus a more efficient rocket engine overall. All improvements to its subcomponents will inherently end up benefiting SpaceX’s BFR booster and spaceship, the latter of which is already nearing initial prototype construction.
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- SpaceX’s current Texas facilities feature a test stand for Raptor, the engine intended to power BFR and BFS to Mars. (SpaceX)
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- SpaceX’s Raptor proceeds through the complex process of ignition. (SpaceX)
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- SpaceX’s subscale Raptor engine has completed more than 1200 seconds of testing in less than two years. (SpaceX)
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- SpaceX’s three-bay Raptor test stand as of April 17. The middle bay is currently home to the subscale Raptor test program. (Aero Photo)
While SpaceX cut its original Raptor specifications by roughly 50% compared to its 2016 goals, it appears that the company’s ambitions for the downsized Raptor are smaller in name only. In a May 2018 presentation, Chief of Propulsion Tom Mueller foreshadowed those future ambitions while humbly acknowledging that the Merlin 1D powering Falcon 9 and Heavy is already a masterpiece of engineering: “Merlin holds the thrust to weight record for now… but Raptor’s coming.”
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Elon Musk has firmly denied recent media reports suggesting that SpaceX has reduced its target valuation for an upcoming initial public offering.
The denial came directly from the SpaceX and Tesla frontman on his social media platform X, where he responded with a single word, “False,” to a post from ZeroHedge that cited Bloomberg sources.
This swift rebuttal underscores Musk’s ongoing effort to manage speculation surrounding one of the most anticipated market debuts in recent history.
False
— Elon Musk (@elonmusk) May 29, 2026
According to the disputed reports, SpaceX had lowered its IPO valuation goal to at least $1.8 trillion from previous ambitions exceeding $2 trillion.
The claims emerged amid growing anticipation for the company’s confidential S-1 filing, which positions it for a potential public listing as early as June.
Some had pointed to strong revenue growth, particularly from the Starlink satellite internet service, which contributed heavily to the firm’s 2025 figures of $18.7 billion. Yet challenges persist in other areas, including substantial investments and losses tied to ambitious projects like Starship development and artificial intelligence initiatives, which plan to make life multiplanetary eventually.
Musk’s response highlights a pattern in which he actively counters what he views as inaccurate portrayals of his companies’ trajectories.
SpaceX, already valued privately at extraordinary levels, stands as a cornerstone of Musk’s empire alongside Tesla and xAI. The entrepreneur has long emphasized the transformative potential of reusable rockets and global broadband access, factors that fuel investor enthusiasm despite operational hurdles.
By rejecting the valuation downgrade narrative, Musk signals confidence in SpaceX’s fundamentals and its readiness for public markets on terms favorable to its long-term vision. People have been waiting a very long time to invest in SpaceX, and the valuation, as well as the introductory share price, is not going to need adjusting.
They’ll have plenty of suitors.
This episode reflects broader dynamics in the technology sector, where rumors often swirl around high-profile entities. Musk’s direct engagement with media narratives serves to maintain transparency and control the narrative around his ventures.
As SpaceX prepares for greater scrutiny in public markets, the founder’s denial reinforces optimism about its prospects. Supporters argue that the company’s innovative edge positions it for enduring success, far beyond short-term valuation debates. With the denial now public, attention turns to forthcoming regulatory filings that could provide clearer insights into SpaceX’s strategy and financial health.
The coming weeks promise to reveal more about how SpaceX will transition into a publicly traded powerhouse.
Tesla’s dreams of operating a fully autonomous ride-hailing platform just took a massive step toward reality, as two separate events have indicated the company is perhaps closer than ever to achieving self-driving as a product.
On Thursday, Tesla was granted authorization by the State of Texas to operate driverless vehicles in a commercial manner. On May 28, Senate Bill 2807, passed by the 89th Texas Legislature, took effect after being passed back on September 1, 2025.
The bill establishes a statewide regulatory framework requiring authorization from the Texas Department of Motor Vehicles for companies to operate automated vehicles commercially on Texas roads.
This covers driverless, or SAE Level 4+, operations for passenger transport, meaning Robotaxi, or freight.
Tesla and other companies can self-certify their vehicles and tech as long as they:
- Operate in compliance with Texas traffic laws
- Maintain proper registration, title, and insurance
- Use compliant automated driving systems
- Record onboard activity and handle system failures and glitches safely.
The new authorization, which was first reported by James Stephenson on X, allows companies to utilize their own processes to determine if their vehicles are ready to operate without drivers.
🚨BREAKING:
Tesla has been authorized by the State of Texas to operate driverless vehicles commercially under the new law that took effect today, May 28th, 2026. Tesla has officially self-certified the software running on its robotaxis as Level 4. $TSLA pic.twitter.com/KSJdsvlaW5— James Stephenson (@ICannot_Enough) May 28, 2026
It is a rule that expedites the entire approval process, keeping agencies out of a usually long, lengthy, and frustrating task that is essential to technological advancements. It essentially means Tesla can launch commercial Robotaxi operations at this point.
On the very same day, Tesla continued the momentum as CEO Elon Musk shared a video of Cybercab units autonomously driving off the property at Gigafactory Texas. This is a major step in the story of the Cybercab.
Mass production of the Cybercab started at Giga Texas in April, and it is already heading out of the factory on its own.
Cybercab driving itself out of the GigaTexas factory pic.twitter.com/EwAMVVDjYy
— Elon Musk (@elonmusk) May 28, 2026
These two major events mark a drastic step forward in Tesla’s progress toward Cybercab and the permissions it needs to operate a self-driving ride-hailing service. Tesla is now able to operate autonomously under Texas law by self-certifying, and with the potentially imminent rollout of Cybercab, Tesla’s autonomous dreams are starting to take serious shape.
Elon Musk
The Tesla and SpaceX merger everyone is talking about is quietly building
Tesla and SpaceX may be closer to merging than Wall Street or either company is admitting.
Elon Musk has reportedly discussed merging Tesla and SpaceX with people close to him, according to CNBC, which cited sources familiar with the conversation. Tesla employees have long expected such a transaction and the topic is openly discussed internally, according to internal sources. With SpaceX is days away from kicking off its Wall Street roadshow for what could be the largest IPO in market history, this would be the first time the company will have public market currency to execute a stock-for-stock deal with Tesla.
The financial logic for a merger would make sense. A combined SpaceX and Tesla would create a conglomerate spanning rockets, satellites, electric vehicles, AI infrastructure, and energy storage valued at roughly $3.35 trillion to $3.6 trillion based on SpaceX’s IPO target range and Tesla’s current market capitalization. The two companies are already more intertwined than most people realize. SpaceX bought $697 million worth of Tesla Megapack systems for xAI data centers and $131 million worth of Cybertrucks. Tesla invested $2 billion in xAI, which subsequently merged with SpaceX. Past transactions also include Tesla selling solar equipment and parts to SpaceX, and SpaceX helping with Cybertruck materials.
Will Tesla join the fold? Predicting a triple merger with SpaceX and xAI
Musk himself signaled where this was heading in November 2025 when he posted on X, “My companies are, surprisingly in some ways, trending towards convergence.” Tesla and SpaceX announced a joint semiconductor fabrication facility in Austin called Terafab on the Gigafactory Texas campus, covering two advanced chip factories, with one serving Tesla’s AI needs for vehicles and Optimus robots, the other targeting space-based data centers under SpaceX’s infrastructure vision.
Wedbush analyst Dan Ives places the probability of a merger at 80% to 90% with a target completion in the first half of 2027. The mechanics of a deal became possible the moment SpaceX filed its S-1. Legal experts said a merger likely would not spark antitrust issues but would raise concerns among shareholders in each company, with questions around which company would be the parent, how a stock swap would take place, and who determines the appropriate price. Musk holds about 20% of Tesla’s equity but controls 85.1% of SpaceX’s voting power through a super-voting share class, meaning he would largely be negotiating the terms with himself.
Not everyone is convinced the timing is imminent. Traders on Kalshi place only 33% odds that a merger will happen before May 2027. The more immediate concern for Tesla shareholders is whether the SpaceX IPO pulls capital and Musk’s attention away from Tesla before any merger consolidates the upside for both.
What is clear is that the structural groundwork is already being laid. The Terafab announcement, the xAI merger, the shared supply chain, the cross-company balance sheet transactions, and now the IPO all point in the same direction. Whether the merger follows in 2027 or later, the two companies are already operating more like divisions of a single entity than independent competitors.
Elon Musk strikes down reports on SpaceX IPO rumors
Tesla’s Robotaxi dreams just took a massive step toward reality
