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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.
Elon Musk
Tesla FSD in Europe vs. US: It’s not what you think
Tesla FSD is approved in the Netherlands, but the European version differs from what US drivers use.
On April 10, 2026, the Dutch vehicle authority RDW granted Tesla the first European type approval for Full Self-Driving Supervised, making the Netherlands the first country on the continent to authorize Tesla’s semi-autonomous system for customer use on public roads.
As Teslarati reported, the RDW approval followed 18 months of testing, more than 1.6 million kilometers driven on EU roads, 13,000 customer ride-alongs, and documentation covering over 400 compliance requirements. Tesla Europe had been running public demo drives through cities like Amsterdam and Eindhoven since early 2026, giving passengers their first experience of the system on European streets.
The European version of FSD is not the same software US drivers use. The RDW’s own statement is direct, noting that the software versions and functionalities in the US and Europe “are therefore not comparable one-to-one.” We’ve compile a table below that captures the most significant differences between US-based Tesla FSD vs. European Tesla FSD that’s based on what regulators and Tesla have publicly confirmed.
| Feature | FSD US | FSD Europe (Netherlands) |
| Regulatory framework | Self-certification, post-market oversight | Pre-market type approval required (UN R-171 + Article 39) |
| Hands requirement | Hands-off permitted on highway | Hands must be available to take over immediately |
| Auto turning from stop lights | Available — navigates intersections, turns, and traffic signals autonomously | Available in EU build — confirmed in Amsterdam demo footage handling unprotected turns and signalized intersections |
| Driving modes | Multiple profiles including a more aggressive “Mad Max” mode | EU build is more conservative by default and errs on the side of restraint when it cannot confirm the limit |
| Summon | Available — Smart Summon navigates parking lots to driver | Status unclear — not confirmed as part of the RDW-approved feature set; urban FSD approval targeted separately for 2027 |
| Driver monitoring | Camera-based eye tracking | Stricter continuous monitoring with more frequent intervention alerts |
| Software version | FSD v14.3 | EU-specific builds that must be separately validated by RDW |
| Geographic restriction | US, Canada, China, Mexico, Australia, NZ, South Korea | Netherlands only; EU-wide vote pending summer 2026 |
| Subscription price | $99/month | €99/month |
| Full urban FSD scope | Available | Partial — separate urban application planned for 2027 |
The approval comes as Tesla is under real pressure to grow FSD subscriptions globally. Musk’s 2025 CEO compensation package, approved by shareholders, includes a milestone requiring 10 million active FSD subscriptions as one condition for his stock awards to vest. Tesla hit one million subscriptions during its Q4 2025 earnings call, which is a meaningful start, but still a long way from the target. Opening Europe as a market for subscriptions, rather than just hardware sales, directly accelerates that number.
Tesla has said it anticipates EU-wide recognition of the Dutch approval during summer 2026, which would extend FSD access to Germany, France, and other major markets through a mutual recognition process without each country repeating the full 18-month review. That timeline is Tesla’s projection, not a confirmed regulatory outcome. As Musk acknowledged at Davos in January 2026, “We hope to get Supervised Full Self-Driving approval in Europe, hopefully next month.”
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Tesla’s troublesome Auto Wipers get a major upgrade
Tesla has quietly deployed a major over-the-air (OTA) update across its entire fleet, implementing a new patent that could finally solve one of the most complained-about features in its vehicles: the Auto Wipers.
One of Tesla’s most complained-about features is that of the Auto Wipers, but they have recently received a major upgrade that impacts every vehicle in the company’s fleet, a company executive confirmed.
Tesla has quietly deployed a major over-the-air (OTA) update across its entire fleet, implementing a new patent that could finally solve one of the most complained-about features in its vehicles: the Auto Wipers.
Confirmed by senior Tesla AI engineer Yun-Ta Tsai on April 10, the improvement is based on patent US 20260097742 A1. It introduces an “energy balance model” that adds a tactile, physics-driven layer to the existing camera-based system—without requiring any new hardware.
🚨 Tesla has already implemented a new patent that improves the accuracy of the Auto Wiper system https://t.co/QjjKHKxSNv pic.twitter.com/mEbd04oJAu
— TESLARATI (@Teslarati) April 10, 2026
Tesla drivers have griped about auto wipers since the company ditched traditional rain sensors in favor of Tesla Vision around 2018.
Owners routinely report the wipers failing to activate in light drizzle or mist, leaving windshields streaked and visibility dangerously reduced. Just as often, they formerly blasted into high-speed mode on dry, sunny days, screeching across glass and risking scratches or premature blade wear.
This is a rare occurrence anymore, but many owners still report the feature having the wipers perform at the incorrect speed or frequency when precipitation is falling.
Tesla has tried repeatedly to fix the problem through software alone.
Early “Deep Rain” initiatives and the 2023 Autowiper v4 update used multi-camera video and refined neural networks, with Elon Musk promising “super good” performance. The 2024.14 update added manual sensitivity boosts, and later FSD versions claimed further gains. Yet complaints persisted.
Elon Musk apologizes for Tesla’s quirky auto wipers, hints at improvements
Vision systems struggle with edge cases—glare, bugs, reflections, or faint mist—because they rely purely on visual inference rather than physical detection
The new patent takes a different approach. The car’s computer constantly measures electrical power delivered to the wiper motor. It subtracts predictable losses—internal motor friction, linkage drag, and aerodynamic resistance—leaving only the friction force between the rubber blade and windshield glass.
Water lubricates the glass, sharply reducing friction; dry or icy surfaces increase it dramatically. This real-time “tactile” data acts as an independent check on the camera’s visual cues, instantly shutting down false triggers on dry glass and fine-tuning speed for actual rain.
The system can also detect ice and auto-activate defrost heaters, while long-term friction trends alert drivers when blades need replacing.
By fusing vision with precise motor-load physics, Tesla has created a hybrid sensor that is both elegant and cost-free. Owners have waited years for reliable auto wipers; this OTA rollout may finally deliver them.
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Tesla Roadster unveiling set for this month: what to expect
As Tesla finally edges toward production and an updated reveal, enthusiasts aren’t asking for compromises; they’re demanding the original vision be honored. Here are five clear expectations that will come with the vehicle’s unveiling, which is still set for later this month, hopefully.
The Tesla Roadster has been the ultimate carrot on a stick since its 2017 unveiling. Promised as the fastest production car ever made, with 0-60 mph in under two seconds and a top speed over 250 mph, it has endured years of delays.
As Tesla finally edges toward production and an updated reveal, enthusiasts aren’t asking for compromises; they’re demanding the original vision be honored. Here are five clear expectations that will come with the vehicle’s unveiling, which is still set for later this month, hopefully.
Performance and Safety Do Not Go Hand in Hand, and That’s the Point
The Roadster is not a family sedan or a daily commuter. It is a no-holds-barred supercar meant to embarrass six-figure exotics on track days. Tesla should resist the temptation to load it with every passive-safety nanny and electronic guardian that dulls the raw feedback drivers crave.
Owners want to feel the road, not be shielded from it. Strip away unnecessary electronic limits so the car can deliver the visceral thrill Elon Musk originally described. Safety ratings will still be strong because of Tesla’s structural excellence, but the Roadster’s mission is speed, not coddling.
He said late last year:
“This is not a…safety is not the main goal. If you buy a Ferrari, safety is not the number one goal. I say, if safety is your number one goal, do not buy the Roadster…We’ll aspire not to kill anyone in this car. It’ll be the best of the last of the human-driven cars. The best of the last.”
Musk was clear that this will not be a car that will be the safest in Tesla’s lineup, but that’s the point. It’s not made for anything other than pushing the limits.
Tesla Needs to Come Through on a HUGE Feature
The Roadster unveiling would be wildly disappointing if it were only capable of driving. Tesla has long teased the potential ability to float or hover, and they need to come through on something that is along those lines.
The SpaceX cold-gas thruster package was never a joke. Musk, at one time, explicitly said owners could opt for a set of thrusters capable of lifting the car off the ground for short hops or dramatic launches. That feature is what separates the Roadster from every other hypercar on the planet.
If the production version arrives without it—or with a watered-down “maybe later” version—enthusiasts will feel betrayed. Deliver the thrusters, make them functional, and let the Roadster literally hover above the competition.
An Updated Design Might Be Warranted
It’s been nine years since Tesla first rolled off the next-gen Roadster design and showed it to the world.
The 2017 concept still looks sharp, but eight years is an eternity in automotive styling. The sharp lines and aggressive stance now compete against the angular Cybertruck and the next-generation vehicles rolling out of Fremont and Austin.
Tesla Roadster patent hints at radical seat redesign ahead of reveal
A subtle refresh, maybe with sharper headlights, revised aero elements, and modern materials, would keep the Roadster feeling current without losing its identity. Fans don’t want a complete redesign, just enough evolution to prove Tesla still cares.
Self-Driving Isn’t a Necessity for the Tesla Roadster
Full Self-Driving hardware and software belong in the Model 3, Model Y, and the upcoming robotaxi—not in a two-seat rocket built for canyon carving. The Roadster’s entire appeal is the direct connection between driver, steering wheel, and asphalt.
Offering FSD as standard would dilute the purity that separates it from every other Tesla. Make autonomy an optional delete or simply omit it. Let the Roadster remain the purest driving machine in the lineup, because that’s what it is all about.
Tesla Needs to Come Through on the Unveiling Timeline
The last thing Tesla needs right now is another complaint about not hitting timelines or expectations. This unveiling has already been pushed back one time, from April 1 to “probably in late April.”
Repeated delays have tested even the most patient fans. Whatever date the company now sets for the next major reveal or start of production must be met. No more “next year” promises. The Roadster has waited long enough. When it finally arrives, it must feel worth every extra month.
If Tesla hits these five marks, the Roadster won’t just be another fast car—it will be the machine that redefines what a Tesla can be. The world is watching.
Tesla FSD in Europe vs. US: It’s not what you think
Tesla’s troublesome Auto Wipers get a major upgrade
