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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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SpaceX stock did the opposite of what most of Wall Street expected this week, when the day designed to be its most dangerous turned into a rally, and the rally kept going.
Thursday marked the first major lockup expiration since SpaceX’s June IPO, making roughly 911.5 million insider held shares eligible to trade for the first time, more than doubling the company’s public float. Analysts and short sellers had spent weeks bracing for a flood of selling, especially after the stock fell 13 percent following its first earnings report as a public company on Tuesday. Instead, shares rose 6.1 percent Thursday to close at $114.92, and by Friday they were trading near $129, up more than another 12 percent on the day.
SpaceX shorts get warned by Musk ally, echoing Tesla’s early struggles
The setup made the outcome notable. Short interest had climbed to roughly 34 percent of the float heading into earnings, among the highest of any large cap stock, with about 95 percent of available shares to borrow already on loan. CEO Elon Musk warned short sellers twice in the weeks before the lockup, writing on X that “the survival probability of firms who maintain a significant short position in SpaceX over time is very low,” then following up on the morning of earnings with “I try to warn them, but they just double down.”
When the newly unlocked shares hit the market and the selloff never showed up, some of that short position appears to have started unwinding. TipRanks reported that options activity shifted toward bullish strategies like put selling and risk reversals following the rally, with roughly $600 million in options premium trading Thursday alone. Retail buyers also stepped in during the earnings dip, according to Vanda Research.
The fundamentals behind the stock have not changed much in a week. SpaceX’s revenue nearly doubled year over year to $7.8 billion, with Starlink subscribers doubling to 12 million and the company’s AI segment growing 247 percent. What spooked investors on Tuesday was the spending side. Capital expenditures jumped to more than $18 billion for the quarter, up from $2.8 billion a year earlier, with AI investment alone rising from $749 million to $15.8 billion. Wall Street remains split on whether that spending is building infrastructure SpaceX needs or outrunning what the business can currently support, a debate Teslarati has tracked since shares first came under pressure.
None of that resolves the bigger question hanging over the stock. Thursday’s release was only the first of nine staggered lockup tranches, with roughly $800 billion worth of additional shares scheduled to become eligible through October, and Musk’s own stake stays locked until next June. If this week is any indication, the market is treating that supply as something it can absorb rather than something to fear, at least for now.
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News
The Boring Company’s newest Vegas Station has a permit quietly waiting behind it
Sahara Las Vegas opened a new Vegas Loop station, joining an exclusive two resort transit club.
Sahara Las Vegas opened a new Vegas Loop station Thursday, giving The Boring Company’s underground transit system its northernmost stop yet on the Strip. The station sits at Sahara’s Paradise Road entrance, on the southeast corner of Las Vegas Boulevard and Sahara Avenue, and connects riders to the Las Vegas Convention Center, other Strip resorts on the network and, eventually, Harry Reid International Airport.
The addition makes Sahara the second resort, after Fontainebleau opened its own station in January, to get a stop built at street level rather than tucked into the property itself. Sahara now joins Westgate as the only two Strip resorts offering both a Vegas Loop station and a stop on the Las Vegas Monorail, giving guests two separate ways to get around without leaving the property.
The Boring Company just doubled its tunneling power in Nashville
The bigger news buried in Thursday’s announcement is what comes next. Boring Company has already secured its first permit to tunnel north of Sahara Avenue, extending the network beyond where it currently ends, even though permits to push the Loop toward downtown Las Vegas still haven’t been granted. Crews are also working on a two mile dual tunnel line running from Westgate to a planned station at 4744 Paradise Road, just north of Tropicana Avenue, that Las Vegas Convention and Visitors Authority CEO Steve Hill has said the company hopes to open in time for November’s Las Vegas Grand Prix.
Ridership has grown alongside the buildout. The Loop moved roughly 82,000 passengers during CONEXPO in early March, a total the company highlighted on its own X account at the time, and the system has now carried more than 4 million passengers through 11 open stations since it began running in 2021. The airport connector tunnels, meant to give the Loop a direct link to Harry Reid, have slipped past their original first quarter target and remain under construction, with Boring Company director Mike Baier saying that a full opening is still a few months out.
For Sahara, the calculation is straightforward. Convention traffic drives a large share of Loop ridership, and a station at the property’s front door gives conventiongoers one more reason to book rooms on the Strip’s north end instead of closer to the convention center itself.
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Elon Musk
Tesla’s mysterious Robovan makes a sneak peek with Optimus in Terafab video
Elon Musk shared a new Terafab video showing Optimus, Robovans, and a stunningly futuristic campus.
Elon Musk posted a new video of Terafab on X Thursday morning, and the most eye-catching details in it were not the building itself, but two products still awaiting production: Optimus and the Robovan.
The concept render, credited to SpaceX, shows Optimus robots working the grounds of the roughly 2.5-mile-long facility planned for the Gibbons Creek site in Grimes County, while a Robovan glides along an elevated roadway cutting through the building itself, sharing the frame with a Tesla Semi and a Cybercab.
Robovan is the boxy, driverless people and cargo mover Musk unveiled alongside Cybercab at Tesla’s “We, Robot” event in October 2024. He pitched it as a way to move up to 20 passengers at once, or handle freight instead, at a target cost he claimed could fall under a dollar a mile, with no steering wheel or pedals, the same layout as Cybercab. Nearly two years later, Robovan still has no confirmed production timeline and has not shown up in any factory footage, which makes Thursday’s render one of the only recent looks at the vehicle in any form.
Terafab Texas will be the largest and most valuable building on Earth by far.
And it will be stunningly beautiful. pic.twitter.com/4NweOqTL7y
— Elon Musk (@elonmusk) August 6, 2026
Optimus has moved further along. Tesla began converting Fremont’s old Model S and Model X assembly line into a Gen 3 Optimus production line earlier this year, and Musk visited the site on July 1 to mark the changeover. A second, larger Optimus plant is under construction at Giga Texas, targeting volume production in summer 2027 and eventual capacity of 10 million units a year. Tesla AI lead Ashok Elluswamy said this month the robot has “big shoes to fill” in replacing the S and X line, while Musk has repeatedly called Optimus the company’s biggest product of any kind, with a long-term price he has pegged between $20,000 and $30,000.
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Check out the “Robovan” from @Tesla
📸: @Teslarati pic.twitter.com/D4es2i9NUe
— TESLARATI (@Teslarati) October 11, 2024
“Terafab Texas will be the largest and most valuable building on Earth by far,” Musk wrote alongside the clip. “And it will be stunningly beautiful.”
One quote post summed up the reaction: “Futuristic scene with RoboVan + Cybercab + Tesla Semi + Optimus.”
Beyond the vehicles, the architecture wrapped around them stands out too. The building’s facade is canted at sharp angles, with illuminated horizontal bands running through what appears to be a multi level interior visible from outside. Below the elevated roadway, pedestrians walk along a plaza next to a reflecting pool, and the skyline behind the campus is dotted with angular spires that read more like sculpture than infrastructure, a departure from the strictly utilitarian look of Gigafactory Texas or Starbase.
The timing tracks with what Terafab representative Riley Trennell told Grimes County residents on Wednesday, when he said renderings of the facility would be released “within days.” Musk’s post followed less than 24 hours later, and Texas Governor Greg Abbott’s office sent out its own release Thursday confirming the project. As Teslarati reported this morning, Terafab’s tax abatement agreements with Grimes County are now signed and active, and SpaceX has sent the county its first $10 million payment under that deal. The dollar figure tied to this phase of construction, per Reuters, is $16.8 billion, one of the first hard capital expenditure numbers attached to Terafab since Musk unveiled the joint Tesla-SpaceX-xAI venture in March.Reaction on X ranged from enthusiastic to skeptical. “God Bless Texas! Everything is bigger and better in Texas!” one reply read. Another was more measured: “Terafab in a decade…..”
Whether the finished building matches the render is a separate question from whether Musk wanted people talking about the render itself. Less than a day after posting, the video had already crossed 5.5 million views.
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Elon Musk and SpaceX shrugs off the trading day Wall Street feared most
The Boring Company’s newest Vegas Station has a permit quietly waiting behind it
