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SpaceX to use superalloys in Mars rocket Raptor engines, says Elon Musk

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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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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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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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SpaceX just got pulled into the biggest Weapons Program in U.S. history

SpaceX joins the Golden Dome software group, deepening its role in America’s most expensive defense program.

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US Golden Dome space defense system (Concept render by Grok)

SpaceX has joined a nine-company group developing the core operating software for the Golden Dome, America’s next-generation missile defense system. According to a Bloomberg report, SpaceX is focused on integrating satellite communications for military operations and is working alongside eight other defense and artificial intelligence companies, including Anduril Industries, Palantir Technologies, and Aalyria Technologies, to build software connecting missile defense capabilities.

The Golden Dome concept dates back to President Trump’s 2024 campaign, and on January 27, 2025, he signed an executive order directing the U.S. Armed Forces to construct the system before the end of his term. The system is planned to employ a constellation of thousands of satellites equipped with interceptors, with data centers in space providing automated control through an AI network.

FCC accepts SpaceX filing for 1 million orbital data center plan

Space Force Gen. Michael Guetlein, director of the Golden Dome initiative, has described the software layer as a “glue layer” that would enable officers to manage and control radars, sensors, and missile batteries across services. The consortium is aiming to test the platform this summer.

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Trump selected a design in May 2025 with a $175 billion price tag, expected to be operational by the end of his term in 2029, though the Congressional Budget Office projected the cost could reach $831 billion over two decades.

The Golden Dome role is only the latest in a string of military wins for SpaceX. As Teslarati reported, the U.S. Space Force awarded SpaceX a $178.5 million task order on April 1, 2026 to launch missile tracking satellites for the Space Development Agency, covering two Falcon 9 launches beginning in Q3 2027. That came on top of more than $22 billion in government contracts held by SpaceX as of 2024, per CEO Gwynne Shotwell, spanning NASA resupply missions, classified intelligence satellites through its Starshield program, and military broadband.

The accumulation of defense contracts, now including a seat at the table on the most expensive weapons program in U.S. history, positions SpaceX as the dominant infrastructure provider for American national security in space. With a SpaceX IPO still on the horizon, each new contract adds weight to what is already one of the most consequential companies in aerospace history, raising real questions about how much of America’s defense architecture will depend on a single private operator before it ever trades publicly.

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Tesla pulls back the curtain on Cybercab mass production

Tesla’s Cybercab drives itself off the Gigafactory Texas line in a striking new production video.

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Tesla Cybercab production units rolling off the factory line in Gigafactory Texas (Credit: Tesla)

Tesla has provided a first look from inside a production Cybercab as it drove itself off the assembly line at Gigafactory Texas. The video footage, posted on X, opens on the factory floor with robotic arms and assembly equipment visible through the Cybercab windshield, and follows the car through a branded tunnel marked “Cybercab”, before autonomously navigating itself to a holding lot.

The first Cybercab rolled off the Giga Texas production line on February 17, 2026, with Musk writing on X, “Congratulations to the Tesla team on making the first production Cybercab.” April marked the official shift to volume production. The Giga Texas line is being prepared to produce hundreds of units per week, with 60 units already spotted on the Gigafactory campus earlier this month.


The Cybercab was first revealed publicly at Tesla’s “We, Robot” event in October 2024 at Warner Bros. Studios in Burbank, California, where 20 pre-production units gave attendees rides around the studio lot. Musk said he believed the average operating cost would be around $0.20 per mile, and that buyers would be able to purchase one for under $30,000. The two-seat design is deliberate. Musk noted that 90 percent of miles driven involve one or two people, making a compact two-passenger vehicle the most efficient configuration for a fleet-scale robotaxi. Eliminating rear seats also removes complexity and cost, supporting that sub-$30,000 target.

Tesla’s annual production goal is 2 million Cybercabs per year once several factories reach full design capacity. The Cybercab has no steering wheel, no pedals, and relies entirely on Tesla’s vision-based FSD system. What the video shows is the first evidence of that system working not as a demo, but as a production reality, driving itself off the line and into the world.

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Elon Musk talks Tesla Roadster’s future

Elon Musk confirmed the Roadster as Tesla’s last manually driven car, with a debut coming soon.

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Tesla Roadster driving along sunset cliff (Credit: Grok)

During Tesla’s Q1 2026 earnings call on April 22, Elon Musk made a brief but notable comment about the long-awaited next generation Roadster while describing Tesla’s future vehicle lineup. “Long term, the only manually driven car will be the new Tesla Roadster,” he said. “Speaking of which, we may be able to debut that in a month or so. It requires a lot of testing and validation before we can actually have a demo and not have something go wrong with the demo.”

That single statement is the entire Roadster update from yesterday’s call, and while it represents another timeline shift, it comes as no surprise with Tesla heads-down-at-work on the mass rollout of its Robotaxi service across US cities, and the industrial scale production of the humanoid Optimus.

The fact that Musk specifically framed the Roadster as the last manually driven Tesla is significant on its own. As the rest of the lineup moves toward full autonomy, the Roadster becomes something rare in the Tesla-sphere by keeping the driver in control. Driving enthusiasts who buy a $200,000 supercar are not doing so to be passengers. They want the physical connection to the road, the feel of acceleration under their own input, and the experience of controlling something with that level of performance. FSD, however capable it becomes, removes that entirely. The Roadster signals that Tesla understands this distinction and is building a car specifically for the people who consider driving itself the point.

Tesla isn’t joking about building Optimus at an industrial scale: Here we go

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The specs for the Roadster Musk has teased over the years are genuinely unlike anything in production. The base model targets 0 to 60 mph in 1.9 seconds, a top speed above 250 mph, and up to 620 miles of range from a 200 kWh battery. The optional SpaceX package takes it further, rumored to add roughly ten cold gas thrusters operating at 10,000 psi, borrowed directly from Falcon 9 rocket technology. With thrusters, Musk has claimed 0 to 60 mph in as little as 1.1 seconds. In a 2021 Joe Rogan interview he went further, stating “I want it to hover. We got to figure out how to make it hover without killing people.” Tesla filed a patent for ground effect technology in August 2025, suggesting the hover concept has not been abandoned. The starting price remains $200,000, with the Founders Series requiring a $250,000 full deposit. Some reservation holders placed those deposits in 2017 and are approaching a full decade of waiting.

With production now targeted for 2027 or 2028 at the earliest, the Roadster remains Tesla’s most audacious promise and its longest-running delay. But if what Musk is testing lives up to even half of what he has described, the demo alone should be worth waiting for.

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