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SpaceX CEO Elon Musk explains Starship’s ‘transpiring’ steel heat shield in Q&A
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.
When going to ~1750 Kelvin, specific heat is more important than latent heat of vaporization, which is why cryogenic fuel is a slightly better choice than water
— Elon Musk (@elonmusk) January 22, 2019
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”.
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- Starhopper and SpaceX’s spartan assembly facilities are pictured here, showing the inside of the aft section and a completed tank dome. (Austin Barnard)
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- Starship has been shown with actuating fins and canard wings since SpaceX’s September 2018 update. (SpaceX)
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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- Starship’s first full-scale prototype is being rapidly assembled in South Texas. (NASASpaceflight – bocachicagal)
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- Starship’s first full-scale prototype is being rapidly assembled in South Texas. (NASASpaceflight – bocachicagal)
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- Meanwhile, giant 9m-diameter tank domes are being assembled and welded together a few hundred feet away from Starhopper. (NSF – bocachicagal)
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- SpaceX’s Starhopper seen in a January render and a January photo. (SpaceX/Elon Musk)
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- BFS seen standing vertically on the pads of its tripod fins. (SpaceX)
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- A NASA team—via a US Navy aircraft—captured high-resolution, calibrated infrared imagery of Space Shuttle Discovery’s lower surface in addition to discrete instrumentation on the wing, downstream, and on the Boundary Layer Transition Flight Experiment protuberance. In the image, the red regions represent higher surface temperatures. (NASA)
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.
Probability at 60% & rising rapidly due to new architecture
— Elon Musk (@elonmusk) December 27, 2018
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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Tesla makes latest move to remove Model S and Model X from its lineup
Tesla’s latest decisive step toward phasing out its flagship sedan and SUV was quietly removing the Model S and Model X from its U.S. referral program earlier this week.
Tesla has made its latest move that indicates the Model S and Model X are being removed from the company’s lineup, an action that was confirmed by the company earlier this quarter, that the two flagship vehicles would no longer be produced.
Tesla has ultimately started phasing out the Model S and Model X in several ways, as it recently indicated it had sold out of a paint color for the two vehicles.
Now, the company is making even more moves that show its plans for the two vehicles are being eliminated slowly but surely.
Tesla’s latest decisive step toward phasing out its flagship sedan and SUV was quietly removing the Model S and Model X from its U.S. referral program earlier this week.
The change eliminates the $1,000 referral discount previously available to new buyers of these vehicles. Existing Tesla owners purchasing a new Model S or Model X will now only receive a halved loyalty discount of $500, down from $1,000.
The updates extend beyond the two flagship vehicles. New Cybertruck buyers using a referral code on Premium AWD or Cyberbeast configurations will no longer get $1,000 off. Instead, both referrer and buyer receive three months of Full Self-Driving (Supervised).
The loyalty discount for Cybertruck purchases, excluding the new Dual Motor AWD trim level, has also been cut to $500.
NEWS: Tesla has removed the Model S and Model X from the referral program.
New owners also no longer get a $1,000 referral discount on a new Cybertruck Premium AWD or Cyberbeast. Instead, you now get 3 months of FSD (Supervised).
Additionally, Tesla has reduced the loyalty… pic.twitter.com/IgIY8Hi2WJ
— Sawyer Merritt (@SawyerMerritt) March 6, 2026
These adjustments apply only in the United States, and reflect Tesla’s broader strategy to optimize margins while boosting adoption of its autonomous driving software.
The timing is no coincidence. Tesla confirmed earlier this year that Model S and Model X production will end in the second quarter of 2026, roughly June, as the company reallocates factory capacity toward its Optimus humanoid robot and next-generation vehicles.
With annual sales of the low-volume flagships already declining (just 53,900 units in 2025), incentives are no longer needed to drive demand. Production is winding down, and Tesla expects strong remaining interest without subsidies.
Industry observers see this as the clearest sign yet of an “end-of-life” phase for the vehicles that once defined Tesla’s luxury segment. Community reactions on X range from nostalgia, “Rest in power S and X”, to frustration among long-time owners who feel perks are eroding just as the models approach discontinuation.
Some buyers are rushing orders to lock in final discounts before they vanish entirely.
Doug DeMuro names Tesla Model S the Most Important Car of the last 30 years
For Tesla, the move prioritizes efficiency: fewer discounts on outgoing models, a stronger push for FSD subscriptions, and a focus on high-margin Cybertruck trims amid surging orders.
Loyalists still have a narrow window to purchase a refreshed Plaid or Long Range model with remaining incentives, but the message is clear: Tesla’s lineup is evolving, and the era of the original flagships is drawing to a close.
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Tesla Australia confirms six-seat Model Y L launch in 2026
Compared with the standard five-seat Model Y, the Model Y L features a longer body and extended wheelbase to accommodate an additional row of seating.
Tesla has confirmed that the larger six-seat Model Y L will launch in Australia and New Zealand in 2026.
The confirmation was shared by techAU through a media release from Tesla Australia and New Zealand.
The Model Y L expands the Model Y lineup by offering additional seating capacity for customers seeking a larger electric SUV. Compared with the standard five-seat Model Y, the Model Y L features a longer body and extended wheelbase to accommodate an additional row of seating.
The Model Y L is already being produced at Tesla’s Gigafactory Shanghai for the Chinese market, though the vehicle will be manufactured in right-hand-drive configuration for markets such as Australia and New Zealand.
Tesla Australia and New Zealand confirmed the vehicle will feature seating for six passengers.
“As shown in pictures from its launch in China, Model Y L will have a new seating configuration providing room for 6 occupants,” Tesla Australia and New Zealand said in comments shared with techAU.
Instead of a traditional seven-seat arrangement, the Model Y L uses a 2-2-2 layout. The middle row features two individual seats, allowing easier access to the third row while providing additional space for passengers.
Tesla Australia and New Zealand also confirmed that the Model Y L will be covered by the company’s updated warranty structure beginning in 2026.
“As with all new Tesla Vehicles from the start of 2026, the Model Y L will come with a 5-year unlimited km vehicle warranty and 8 years for the battery,” the company said.
The updated policy increases Tesla’s vehicle warranty from the previous four-year or 80,000-kilometer coverage.
Battery and drive unit warranties remain unchanged depending on the variant. Rear-wheel-drive models carry an eight-year or 160,000-kilometer warranty, while Long Range and Performance variants are covered for eight years or 192,000 kilometers.
Tesla has not yet announced official pricing or range figures for the Model Y L in Australia.
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
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
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
Tesla makes latest move to remove Model S and Model X from its lineup
Tesla Australia confirms six-seat Model Y L launch in 2026
