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SpaceX CEO Elon Musk explains Starship’s ‘transpiring’ steel heat shield in Q&A

BFR's booster (Super Heavy) and spaceship (Starship) separate shortly after launch. (SpaceX)

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Speaking in a late-December 2018 interview with Popular Mechanics’ editor-in-chief, SpaceX CEO Elon Musk shared considerable insight into the thought processes that ultimately led him to – in his own words – “convince” his team that the company’s BFR rocket (now Starship and Super Heavy) should pivot from an advanced composite structure to a relatively common form of stainless steel.

Aside from steel’s relative ease of manipulation and affordability, Musk delved into the technical solution he arrived at for an advanced, ultra-reusable heat shield for Starship – build it out of steel and use water (or liquid methane) to wick reentry heat away.

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Although there has been some successful experimental research done on “transpirational” heat shields (relying on the heat capacity of vaporizing liquids or gases to soak up thermal energy during orbital rocket reentries), Musk is by no means wrong when he says that a stainless steel sandwich-hulled spaceship regeneratively cooled by microscopic holes and liquid water or propellant “has never been proposed before”. While the basic concept probably arose somewhere over the last 50-100 years, it does not appear that any serious theoretical or experimental research has been conducted to explore transpiration-cooled metallic heat shields, where metallic thermal protection systems (TPS) are already fairly exotic and unproven in the realm of modern aerospace.

“Very easy to work with steel. Oh, and I forgot to mention: [SpaceX’s high-quality] carbon fiber is $135 a kilogram, 35 percent scrap, so you’re starting to approach almost $200 a kilogram. [301] steel is $3 a kilogram.” – Elon Musk

While Musk’s solution could dramatically simplify what is needed for Starship’s high-performance heat shield, a stainless steel sandwich on half of Starship offers another huge benefit: the spacecraft can still gain many of the mass ratio benefits of stainless steel balloon tanks (metal tanks so thin that they collapse without positive pressure) while retaining structural rigidity even when depressurized. At the end of the day, Musk very well might be correct when he states that a stainless steel Starship can ultimately be more mass-efficient (“lighter”) than a Starship built out of advanced carbon composites, a characteristic he rightly describes as “counterintuitive”.

What does Science™ have to say?

Based on research done in the 2010s by German space agency (DLR), a porous thermal protection material called Procelit 170 (P170) – 91% aluminum oxide and 9% silicon oxide – was cooled from a peak heat of ~1750 C (3200 F) to ~25 C (75 F) during wind tunnel testing, demonstrating that an average of 0.065 kg (~2.3 oz) of water per second would be needed to cool a square meter of P170 to the same degree, assuming a heating rate of around 200 kW/m^2. Given that 300-series stainless steels have a comparatively huge capacity for radiating heat at high temperatures, will be dramatically thinner than Procelit in any given Starship use-case, and will not need to be cooled all the way to 25C/75F during hot operations, the DLR-derived number is barely relevant without another round of wind tunnel tests focused on metallic thermal protection systems. Still, it allows for the creation of a sort of worst-case scenario for BFS/Starship’s water-cooled shield.

Assuming that the windward side of Starship’s regeneratively cooled heat shield has roughly the same surface area as half of a cylinder, 800 m^2 (8600 ft^2) will have to be actively cooled with water, translating to a water consumption rate of approximately 52 kg/s (115 lb/s) if the entire surface is being subjected to temperatures around ~1750 C. That is, of course, a grossly inaccurate generalization, as aerodynamic surfaces dramatically shape, dissipate, and concentrate airflows (and thus heat from friction) in complex and highly specific ways. Much like NASA’s Space Shuttle or DLR’s theoretical SpaceLiner, the reality of reentry heating is that that heat typically ends up being focused at leading edges and control surfaces, which thus require uniquely capable versions of thermal protection (TPS). Shuttle used fragile reinforced carbon-carbon tiles at those hotspots, while DLR was exploring water cooling as a viable and safer alternative for SpaceLiner.

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Aside from heat flux, it’s also unclear when or how long the cooling system will need to be supplied with water during potential Starship reentries. At worst, the spacecraft would need to supply a constant 50+ kg/s throughout a 5+ minute (600+ second) regime of high-velocity, high-drag reentry conditions. Assuming that Starship will need to rely heavily on aerobraking to maintain efficient interplanetary operations, it might have to perform 2+ active-cooling cycles per reentry, potentially requiring a minimum of 15 tons of water per reentry. Given that SpaceX intends (at least as of September 2018) for Starship to be able to land more than 100 tons on the surface of Mars, 15t of water would cut drastically into payload margins and is thus likely an unfeasibly large mass reserve or any given interplanetary mission.

“You just need, essentially, [a stainless-steel sandwich]. You flow either fuel or water in between the sandwich layer, and then you have [very tiny] perforations on the outside and you essentially bleed water [or fuel] through them … to cool the windward side of the rocket.” – SpaceX CEO Elon Musk (Popular Mechanics, December 2018)

The assumptions needed for the above calculations do mean that 30T is an absolute worst-case scenario for a regeneratively-cooled Starship reentry, given that SpaceX may only have to vigorously cool a small fraction of its windward surface and will likely be able to cut more than half of the water needed by allowing Starship’s steel skin to heat quite a lot while still staying well below its melting point (likely around 800C/1500F or higher). This also fails to account for the fact that a regeneratively-cooled stainless steel heat shield would effectively let SpaceX do away with what would otherwise be a massive and heavy ablative heat shield and mounting mechanism. Perhaps the benefits of stainless steel might ultimately mean that carrying around 10-30T of coolant is actually performance-neutral or a minimal burden when all costs and benefits are properly accounted for.

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Musk clearly believes with almost zero doubt that a stainless steel Starship and booster (Super Heavy) is the way forward for the company’s BFR program, and he has now twice indicated that the switch away from advanced carbon composites will actually “accelerate” the rocket’s development schedule. For now, all we can do is watch as the first Starship prototype – meant to perform short hop tests ASAP – gradually comes into being in South Texas.

 


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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 Roadster patent hints at radical seat redesign ahead of reveal

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A newly published Tesla patent could offer one of the clearest signals yet that the long-awaited next-generation Roadster is nearly ready for its public debut.

Patent No. US 20260061898 A1, published on March 5, 2026, describes a “vehicle seat system” built around a single continuous composite frame – a dramatic departure from the dozens of metal brackets, recliner mechanisms, and rivets that make up a traditional car seat. Tesla is calling it a monolithic structure, with the seat portion, backrest, headrest, and bolsters all thermoformed as one unified piece.

The approach mirrors Tesla’s broader manufacturing philosophy. The same company that pioneered massive aluminum castings to eliminate hundreds of body components is now applying that logic to the cabin. Fewer parts means fewer potential failure points, less weight, and a cleaner assembly process overall.

Tesla Roadster Seat Concept Image by TESLARATI

Tesla ramps hiring for Roadster as latest unveiling approaches

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The timing of the filing is difficult to ignore. Elon Musk has publicly targeted April 1, 2026 as the date for an “unforgettable” Roadster design reveal, and two new Roadster trademarks were filed just last month. A patent describing a seat architecture suited for a hypercar, and one that Tesla has promised will hit 60 mph in under two seconds.

The Roadster, originally unveiled in 2017, has been one of Tesla’s most anticipated yet most delayed products. With a target price around $200,000 and engineering ambitions to match, it is being positioned as the ultimate showcase for what Tesla’s technology can do.

The patent was first flagged by @seti_park on X.

Tesla Roadster Monolithic Seat: Feature Highlights via US Patent 20260061898 A1

  1. Single Continuous Frame (Monolithic Construction). The core invention is a seat assembly built from one continuous frame that integrates the seat portion, backrest portion, and hinge into a single component — eliminating the need for separate structural parts and mechanical joints typical in conventional seats.
  2. Integrated Flexible Hinge. Rather than a traditional mechanical recliner, the hinge is built directly into the continuous frame and is designed to flex, and allowing the backrest to move relative to the seat portion. The hinge can be implemented as a fiber composite leaf spring or an assembly of rigid linkages.
  3. Thermoformed Anisotropic Composite Material. The continuous frame is manufactured via thermoforming from anisotropic composite materials, including fiberglass-nylon, fiberglass-polymer, nylon carbon composite, Kevlar-nylon, or Kevlar-polymer composites, enabling a molded-to-shape monolithic structure.
  4. Regionally Tuned Stiffness Zones. The frame is engineered with up to six distinct stiffness regions (R1–R6) across the seat, backrest, hinge, headrest, and bolsters. Each zone can have a different stiffness, allowing precise ergonomic and structural tuning without adding separate components.
  5. Linkage Assembly Hinge Mechanism. The hinge incorporates one or more linkage assemblies consisting of multiple interlocking links with gears, connected by rods. When driven by motors or actuators, these linkages act as a flexible member to control backrest movement along a precise, ergonomically optimized trajectory.
  6. Multi-Actuator Six-Degree-of-Freedom Positioning System. The seat uses four distinct actuator pairs, all controlled by a central controller. These actuators work in coordinated combinations to achieve fore/aft, height, cushion tilt, and backrest rotation adjustments simultaneously.
  7. ECU-Based Controller Architecture. An Electronic Control Unit (ECU) and programmable controller manage all seat actuators, receive user input via a user interface (touchscreen, buttons, or switches), and incorporate sensor feedback to confirm and maintain desired seat positions, essentially making this a software-driven seat system.
  8. Airbag-Integrated Bolster Deployment System. The backrest bolsters (216) are geometrically shaped and sized to guide airbag deployment along a specific, pre-configured trajectory. Left and right bolsters can have different shapes so that each guides its respective airbag along a distinct trajectory, improving occupant protection.
  9. Ventilation Holes Formed into the Backrest. The continuous frame includes one or more ventilation holes formed directly into the backrest portion, configured to either receive airflow into or deliver airflow from the seat frame — enabling passive or active thermal comfort without requiring separate ventilation components.
  10. Soft Trim Recess for Tool-Free Integration. The headrest and backrest portions together define a molded recess, specifically designed to receive and secure a soft trim component (foam, fabric, or cushioning) directly into the continuous frame, eliminating the need for separate attachment hardware and simplifying final assembly.

 

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Elon Musk’s xAI plans $659M expansion at Memphis supercomputer site

The new building is planned for a 79-acre parcel located at 5414 Tulane Road, next to xAI’s Colossus 2 data center site.

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Credit: xAI

Elon Musk’s artificial intelligence company xAI has filed a permit to construct a new building at its growing data center complex outside Memphis, Tennessee. 

As per a report from Data Center Dynamics, xAI plans to spend about $659 million on a new facility adjacent to its Colossus 2 data center. Permit documents submitted to the Memphis and Shelby County Division of Planning and Development show the proposed structure would be a four-story building totaling about 312,000 square feet.

The new building is planned for a 79-acre parcel located at 5414 Tulane Road, next to xAI’s Colossus 2 data center site. Permit filings indicate the structure would reach roughly 75 feet high, though the specific function of the building has not been disclosed.

The filing was first reported by the Memphis Business Journal.

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xAI uses its Memphis data centers to power Grok, the company’s flagship large language model. The company entered the Memphis area in 2024, launching its Colossus supercomputer in a repurposed Electrolux factory located in the Boxtown district.

The company later acquired land for the Colossus 2 data center in March last year. That facility came online in January.

A third data center is also planned for the cluster across the Tennessee–Mississippi border. Musk has stated that the broader campus could eventually provide access to about 2 gigawatts of compute power.

The Memphis cluster is also tied to new power infrastructure commitments announced by SpaceX President Gwynne Shotwell. During a White House event with United States President Donald Trump, Shotwell stated that xAI would develop 1.2 gigawatts of power for its supercomputer facility as part of the administration’s “Ratepayer Protection Pledge.”

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“As you know, xAI builds huge supercomputers and data centers and we build them fast. Currently, we’re building one on the Tennessee-Mississippi state line… 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… 

“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,” Shotwell said.

Shotwell also stated that xAI plans to support the region’s water supply through new infrastructure tied to the project. “We will build state-of-the-art water recycling plants that will protect approximately 4.7 billion gallons of water from the Memphis aquifer each year. And we will employ thousands of American workers from around the city of Memphis on both sides of the TN-MS border,” she said.

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Tesla wins another award critics will absolutely despise

Tesla earned an overall score of 49 percent, up 6 percentage points from the previous year, widening its lead over second-place Ford (45 percent, up 2 points) to a commanding 4-percentage-point gap. The company also excelled in the Fossil Free & Environment category with a 50 percent score, reflecting strong progress in reducing emissions and decarbonizing operations.

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(Credit: Tesla)

Tesla just won another award that critics will absolutely despise, as it has been recognized once again as the company with the most sustainable supply chain.

Tesla has once again proven its critics wrong, securing the number one spot on the 2026 Lead the Charge Auto Supply Chain Leaderboard for the second consecutive year, Lead the Charge rankings show.

This independent ranking, produced by a coalition of environmental, human rights, and investor groups including the Sierra Club, Transport & Environment, and others, evaluates 18 major automakers on their efforts to build equitable, sustainable, and fossil-free supply chains for electric vehicles.

Tesla earned an overall score of 49 percent, up 6 percentage points from the previous year, widening its lead over second-place Ford (45 percent, up 2 points) to a commanding 4-percentage-point gap. The company also excelled in the Fossil Free & Environment category with a 50 percent score, reflecting strong progress in reducing emissions and decarbonizing operations.

Perhaps the most impressive achievement came in the batteries subsection, where Tesla posted a massive +20-point jump to reach 51 percent, becoming the first automaker ever to surpass 50 percent in this critical area.

Tesla achieved this milestone through transparency, fully disclosing Scope 3 emissions breakdowns for battery cell production and key materials like lithium, nickel, cobalt, and graphite.

The company also requires suppliers to conduct due diligence aligned with OECD guidelines on responsible sourcing, which it has mentioned in past Impact Reports.

While Tesla leads comfortably in climate and environmental performance, it scores 48 percent in human rights and responsible sourcing, slightly behind Ford’s 49 percent.

The company made notable gains in workers’ rights remedies, but has room to improve on issues like Indigenous Peoples’ rights.

Overall, the leaderboard highlights that a core group of leaders, Tesla, Ford, Volvo, Mercedes, and Volkswagen, are advancing twice as fast as their peers, proving that cleaner, more ethical EV supply chains are not just possible but already underway.

For Tesla detractors who claim EVs aren’t truly green or that the company cuts corners, this recognition from sustainability-focused NGOs delivers a powerful rebuttal.

Tesla’s vertical integration, direct supplier contracts, low-carbon material agreements (like its North American aluminum deal with emissions under 2kg CO₂e per kg), and raw materials reporting continue to set the industry standard.

As the world races toward electrification, Tesla isn’t just building cars; it’s building a more responsible future.

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