News
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”.
-
- Starhopper and SpaceX’s spartan assembly facilities are pictured here, showing the inside of the aft section and a completed tank dome. (Austin Barnard)
-
- 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.
-
- Starship’s first full-scale prototype is being rapidly assembled in South Texas. (NASASpaceflight – bocachicagal)
-
- Starship’s first full-scale prototype is being rapidly assembled in South Texas. (NASASpaceflight – bocachicagal)
-
- Meanwhile, giant 9m-diameter tank domes are being assembled and welded together a few hundred feet away from Starhopper. (NSF – bocachicagal)
-
- SpaceX’s Starhopper seen in a January render and a January photo. (SpaceX/Elon Musk)
-
- BFS seen standing vertically on the pads of its tripod fins. (SpaceX)
-
- 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.
News
Tesla Semi gets strange-but-understandable comparison from Jay Leno
In a recent interview with MotorTrend, legendary comedian and automotive enthusiast Jay Leno shared his impressions after driving Tesla’s long-range Semi truck, offering one of the most vivid descriptions to date:
The Tesla Semi recently received a strange-but-understandable comparison from automotive enthusiast and former long-time late-night television show host Jay Leno.
In a recent interview with MotorTrend, legendary comedian and automotive enthusiast Jay Leno shared his impressions after driving Tesla’s long-range Semi truck, offering one of the most vivid descriptions to date:
“It’s like driving an office building.”
The comparison may seem quirky—office buildings evoke images of immobility rather than motion—but it aptly conveys the experience of commanding a massive 23,000-pound Class 8 electric truck that delivers sports-car acceleration.
Lenotested the production-spec Long Range model, which is rated for up to 500 miles of range. He was visibly impressed by its performance, noting how the enormous vehicle moves with surprising urgency.
“It’s as fast as a Tesla, but it’s like driving an office building,” he remarked. “It’s this huge thing that moves like right now. You go 500 miles. You get 60% charge in 30 minutes. You’re saving on fuel costs. It seems quite good.”
Jay Leno in new interview on what it’s like to drive the @Tesla Semi:
“I was quite impressed with that. It’s a fast as a Tesla, but it’s like driving an office building. It’s this huge thing that moves like right now. You go 500 miles. You get 60% charge in 30 mins. You’re… pic.twitter.com/YU7tk6a6pV
— Sawyer Merritt (@SawyerMerritt) May 8, 2026
The reaction highlights the cognitive dissonance at the core of the Tesla Semi. Traditional diesel semi-trucks are slow, noisy, and expensive to run. The Semi rewrites the rules with instant torque from its tri-motor electric powertrain, producing up to 800 kW.
Despite its size, the truck feels agile thanks to full electric steering assist, upgraded actuators borrowed from the Cybertruck, and a 48-volt electrical architecture that improves responsiveness and efficiency.
Tesla reports real-world energy consumption below 1.7 kWh per mile for the Long Range version. Megacharger stations can deliver a 60% charge in roughly 30 minutes, making the truck suitable for long-haul operations.
Additional features include an electric Power Take-Off (ePTO) capable of 25 kW for trailer refrigeration or other equipment, and a driver-focused cab with a central seating position for optimal visibility and a quiet, high-tech interior.
Fleet operators stand to benefit significantly from the economics. Diesel trucks often cost nearly one dollar per mile when including fuel, maintenance, and downtime.
Tesla projects the Semi can reduce operating costs to as low as 15 cents per mile through cheaper electricity, regenerative braking that minimizes brake wear, and reduced service requirements. While early deployments, like Pepsi’s, focused on shorter routes, the 500-mile variant targets cross-country applications.
Obstacles remain. A fully loaded tractor-trailer can reach 80,000 pounds, which reduces real-world range compared to the unloaded test conditions. Building out a nationwide Megacharger network will be essential for broader adoption. The Semi also carries a higher upfront price than conventional diesels, though total cost of ownership and available incentives frequently tip the scales in its favor over time.
Tesla Semi hauls fresh Cybercab batch as Robotaxi era takes hold
Leno’s “office building” description resonates because it captures the unexpected thrill of piloting something so large yet so capable. As the trucking industry faces pressure to cut emissions and control rising fuel expenses, the Semi offers a compelling alternative that excels in performance, comfort, and efficiency.
Coming from a man who has driven everything from vintage classics to modern hypercars, Leno’s genuine enthusiasm adds weight to the verdict.
The Tesla Semi is emerging as more than an experimental EV—it represents a practical vision for the future of heavy-duty transport where massive rigs accelerate instantly, and the numbers finally make sense. If fleet results continue to validate the claims, the era of diesel dominance could be drawing to a close.
News
Tesla expands its mass-market color palette in the U.S.
Delivering a fresh splash of color to its lineup, Tesla is giving U.S. buyers two stunning new blue options that are already turning heads.
Tesla has expanded the color palette it offers on its mass market vehicles in the United States, giving buyers of the Model 3 and Model Y a few additional options than before.
Delivering a fresh splash of color to its lineup, Tesla is giving U.S. buyers two stunning new blue options that are already turning heads. Starting on May 8, the automaker updated its North American configurator to introduce Marine Blue on Model Y Premium trims and Frost Blue exclusively on the Model 3 Performance.
Tesla Model Y and Model 3 Premium get Marine Blue for $1000 in the U.S.!
What do you think? pic.twitter.com/3FqMXcnmru
— TESLARATI (@Teslarati) May 8, 2026
The move replaces the long-running Deep Blue Metallic, a staple for over eight years, and brings previously exclusive shades stateside.
Marine Blue, a deep, rich oceanic hue formerly limited to Europe and Asia-Pacific markets, is now available on Model 3 and Model Y RWD and Long Range AWD Premium variants. Priced at a $1,000 upgrade—standard for Tesla’s premium paints—it delivers a sophisticated, metallic finish that shifts beautifully under light.
Tesla Model Y and Model 3 Premium get Marine Blue for $1000 in the U.S.!
What do you think? pic.twitter.com/3FqMXcnmru
— TESLARATI (@Teslarati) May 8, 2026
Tesla North America highlighted the change directly in an official post, confirming Marine Blue as the new flagship blue for non-Performance models.
Frost Blue, on the other hand, is the real crowd-pleaser for enthusiasts. Previously reserved for the flagship Model S and Model X, this lighter, icy metallic shade is now offered at no extra cost on Model 3 Performance and Model Y Performance trims.
Frost Blue now available on Tesla Model 3 Performance 😤 pic.twitter.com/rLOEh4pTkp
— TESLARATI (@Teslarati) May 8, 2026
Performance buyers effectively get a premium color included in the base price, a smart perk that Tesla has extended to higher-end variants across the board. Early in-person sightings and configurator renders show Frost Blue’s cool, modern vibe popping against the cars’ sleek lines, especially with black wheels and red brake calipers.
The timing couldn’t be better. With Tesla pushing refreshed Model 3 and Model Y refreshes amid growing competition, these updates add visual excitement without major redesigns.
Deep Blue Metallic orders are being transitioned to the new shades, according to customer reports and Tesla communications. In the U.S., Puerto Rico, and Mexico, the options are live now; Canada sees limited Frost Blue availability on the Model 3 Performance.
Tesla’s color strategy continues to evolve, borrowing from higher-end models to refresh mass-market EVs. Now that we bid farewell to the Model S and Model X, some of their colors might be available on the more widely available Model 3 and Model Y.
Elon Musk
Tesla Semi’s official battery capacity leaked by California regulators
A California regulatory filing just confirmed the exact battery size inside each Tesla Semi variant.
A regulatory filing published by the California Air Resources Board in April 2026 has put official numbers on what Tesla Semi owners and fleet buyers have long wanted confirmed: the exact battery capacities of both the Long Range and Standard Range Semi truck variants. CARB is California’s independent air quality regulator, and it certifies zero-emission powertrains before they can be sold or operated in the state. When a manufacturer submits a vehicle for certification, the resulting executive order becomes a public document, making it one of the most reliable sources for confirmed production specs on any EV.
The document lists two certified powertrain configurations. The Long Range Semi carries a usable battery capacity of 822 kWh, while the Standard Range version comes in at 548 kWh. Both use lithium-ion NCMA chemistry and share the same peak and steady-state motor output ratings of 800 kW and 525 kW respectively. Cross-referencing Tesla’s published efficiency figure of approximately 1.7 kWh per mile under full load, the 822 kWh pack supports roughly 480 miles of real-world range, which aligns closely with Tesla’s advertised 500-mile figure for the Long Range trim. The 548 kWh Standard Range pack works out to approximately 320 miles, again consistent with Tesla’s stated 325-mile target.
Here is a direct comparison of the two versions based on the CARB filing and published specs:
| Tesla Semi Spec | Long Range | Standard Range |
| Battery Capacity | 822 kWh | 548 kWh |
| Battery Chemistry | NCMA Li-Ion | NCMA Li-Ion |
| Peak Motor Power | 800 kW | 525 kW |
| Estimated Range | ~500 miles | ~325 miles |
| Efficiency | ~1.7 kWh/mile | ~1.7 kWh/mile |
| Est. Price | ~$290,000 | ~$260,000 |
| GVW Rating | 82,000 lbs | 82,000 lbs |
The timing of this certification is not incidental. On April 29, 2026, Semi Programme Director Dan Priestley confirmed on X that high-volume production is now ramping at Tesla’s dedicated 1.7-million-square-foot facility in Sparks, Nevada. A key advantage of the Nevada location is vertical integration: the 4680 battery cells powering the Semi are manufactured in the same complex, eliminating the supply chain bottleneck that had delayed the program for years.
Tesla’s long-term goal is to reach a production capacity of 50,000 trucks annually at the Nevada factory, which would represent roughly 20 percent of the entire North American Class 8 market. With CARB certification now in hand and the production line running, the regulatory and manufacturing groundwork for that target is in place.
Tesla Semi gets strange-but-understandable comparison from Jay Leno
Tesla expands its mass-market color palette in the U.S.
