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 influencers argue company’s polarizing Full Self-Driving transfer decision
Tesla maintains it will honor transfers for orders with initial delivery windows before the deadline and offers full deposit refunds otherwise, citing longstanding fine print that the program is “subject to change at any time.”
Tesla’s decision to tighten its Full Self-Driving (FSD) transfer promotion has ignited fierce debate among owners and enthusiasts.
The company quietly updated its terms in late February 2026, changing the eligibility from “order by March 31, 2026” to “take delivery by March 31, 2026.”
What began as a flexible incentive to boost sales, allowing buyers to transfer their paid FSD (Supervised) to a new vehicle, now excludes many, particularly Cybertruck owners facing delivery delays into summer or later.
Tesla maintains it will honor transfers for orders with initial delivery windows before the deadline and offers full deposit refunds otherwise, citing longstanding fine print that the program is “subject to change at any time.”
The reversal has polarized the Tesla community, with accusations of a “bait-and-switch” clashing against defenses of corporate pragmatism. Many owners who placed orders under the original wording feel betrayed, especially as production backlogs and new unsupervised FSD rollout complicate timelines.
However, Tesla has allowed them to cancel their orders and receive a refund.
Critics of the decision argue that the change disadvantages loyal customers who helped fund FSD development, calling it poor communication and a revenue grab as Tesla pivots toward subscriptions.
Popular influencers have amplified the divide. Whole Mars Catalog struck a measured but firm tone, acknowledging the original “order by” language but emphasizing Tesla’s right to adjust terms. He has continued to defend Tesla in this particular issue:
Sad to see so many fans trashing Tesla with such extreme language.
LIARS!!! PATHETIC!!! And if you aren’t as furious and angry as they are they are you’re “worshipping” and saying “they can do no wrong”.
Let’s get real here. They’re not liars. They offered FSD transfer to us… https://t.co/3Ay7vGaVR6
— Whole Mars Catalog (@wholemars) March 3, 2026
He criticized extreme backlash as “dramatization” and “spoiled kids,” noting the unsupervised FSD era and broader sales challenges make blanket transfers financially risky. Whole Mars advocated for polite outreach to CEO Elon Musk over the issue.
Rather than “calling them out”, I would simply say “Hey Elon, really hoped to be able to do FSD transfer on my cybertruck but the terms changed. Would really appreciate if Tesla could extend this to everyone who ordered before the terms changes”
that would probably work
— Whole Mars Catalog (@wholemars) March 3, 2026
In a contrasting perspective, Dirty TesLA voiced sharper frustration, posting that blocking transfers feels “crazy” and distancing himself from “people that want to worship a corporation and say they can do no wrong.” His stance resonated with owners who view the policy flip as disrespectful to early adopters.
Popular Tesla influencer Sawyer Merritt captured the frustration felt by thousands. In a widely shared thread viewed over 700,000 times, Merritt detailed how pre-change Cybertruck orders now risk losing FSD eligibility unless their initial delivery window falls before March 31.
It’s not a contradiction, it’s a change in policy that Tesla just made an hour ago. I am trying to check if the change is retroactive to all existing orders, including Cybertruck AWD orders, because if it is, that sucks big time.
— Sawyer Merritt (@SawyerMerritt) February 28, 2026
The controversy underscores deeper tensions—between Tesla’s need for revenue discipline and owners’ expectations of goodwill. As FSD evolves toward unsupervised capability, the community remains split: some see the change as necessary business, others as a broken promise. Whether Tesla reconsiders under pressure or holds firm remains to be seen, but it does not appear they are planning to budge.
News
Tesla Semi’s latest adoptee will likely encourage more of the same
Public visibility matters. When shoppers see a trusted name like Ralph’s running clean, high-tech trucks on public roads, skepticism fades. Competitors such as Albertsons, which pre-ordered Semis years ago, and other chains chasing ESG targets now have proof that electric autonomy works in real-world grocery fleets.
The latest adoptee of the Tesla Semi will likely encourage more businesses in the same realm to adopt the all-electric Class 8 truck, as a new company utilizing the Semi has been spotted in Southern California.
A sleek, futuristic Tesla Semi truck branded for Ralph’s Supermarkets was spotted cruising a Los Angeles highway in a viral 13-second dashcam video posted March 2, by X user ChargePozitive.
Tesla Semi Truck in the wild pic.twitter.com/SnQY8ShMMJ
— ChargePozitive ⚡️➕ (@ChargePozitive) March 2, 2026
This sighting confirms Kroger’s March 2025 partnership with Tesla to deploy up to 500 autonomous electric Semis.
While the initial announcement targeted Midwest supply chains, the California appearance under the Ralph’s banner shows the program expanding to Kroger’s West Coast operations. Ralph’s, a staple for millions of Southern California shoppers, is now hauling groceries with the Semi, which has zero tailpipe emissions and claims up to 500 miles of range per charge.
Tesla Semi pricing revealed after company uncovers trim levels
The timing could not be better for sustainable logistics. Traditional trucking accounts for a massive share of retail emissions, but Tesla’s Semi slashes fuel and maintenance costs while leveraging full autonomy to ease driver shortages and improve safety.
Tesla’s expanding Megacharger network, including new sites along major freight corridors and partnerships like the recently-announced one with Pilot Travel Centers, is removing range anxiety and making nationwide scaling realistic. There’s still a long way to go, but things are moving in the right direction.
Public visibility matters. When shoppers see a trusted name like Ralph’s running clean, high-tech trucks on public roads, skepticism fades. Competitors such as Albertsons, which pre-ordered Semis years ago, and other chains chasing ESG targets now have proof that electric autonomy works in real-world grocery fleets.
PepsiCo’s successful pilots already demonstrated viability, and Ralph’s sighting adds retail credibility.
As Tesla ramps high-volume Semi production through 2026, this isn’t an isolated curiosity. Instead, it’s a catalyst. More grocers adopting the platform will accelerate industry-wide decarbonization, cut operating expenses, and deliver tangible environmental wins.
The future of sustainable supply chains is already on the highway, and Ralph’s just made it impossible to ignore.
Moving forward, Tesla hopes to expand the Semi program into other regions, including Europe, which CEO Elon Musk recently said is a total possibility next year.
Elon Musk
Tesla ramps Cybercab test manufacturing ahead of mass production
Tesla still has plans for volume production, which remains between four and eight weeks away, aligning with Musk’s statements that early ramps would be deliberately measured given the Cybercab’s novel architecture and full reliance on Tesla’s vision-based Full Self-Driving technology.
Tesla is seemingly ramping Cybercab test manufacturing ahead of mass production, which is scheduled to begin next month, the company said.
At Tesla’s Gigafactory Texas, production of the Cybercab, the company’s groundbreaking purpose-built Robotaxi vehicle, is accelerating markedly. Drone footage from Joe Tegtmeyer captured striking aerial footage today, revealing what appears to be the largest public sighting of Cyebrcabs to date.
A total of 25 units were observed by Tegtmeyer across the Gigafactory Texas property, marking a clear step-up in testing and validation activities as Tesla prepares for a broader output.
Tesla Cybercab production begins: The end of car ownership as we know it?
In the footage, 14 metallic gold Cybercabs were parked in a tight formation outside the factory exit, showcasing their sleek, autonomous-only design with no steering wheels, pedals, or traditional controls. Another 9 units sat at the crash testing facility, likely undergoing structural and safety validations, while two more appeared at the west end-of-line area for final checks.
Big day for Cybercab at Giga Texas today! Actually, yesterday to kick off March, the production line went into a higher volume & today we see 25 at three main locations, and there were several others I observed driving around too!
I think this may be the largest single grouping… pic.twitter.com/HZDMNv57lJ
— Joe Tegtmeyer 🚀 🤠🛸😎 (@JoeTegtmeyer) March 3, 2026
Tegtmeyer noted additional Cybercabs driving around the complex, hinting at active movement and real-world testing beyond static parking.
This surge follows the first production Cybercab rolling off the line in mid-February 2026, several weeks ahead of the originally anticipated April start.
That milestone, celebrated by Tesla employees and confirmed by CEO Elon Musk, kicked off low-volume builds on the dedicated “unboxed” manufacturing line, a modular process designed to slash costs, reduce factory footprint, and enable faster assembly compared to conventional methods.
Industry observers interpret the jump to dozens of visible units in early March as evidence that Tesla has transitioned into higher-volume test manufacturing.
Tesla still has plans for volume production, which remains between four and eight weeks away, aligning with Musk’s statements that early ramps would be deliberately measured given the Cybercab’s novel architecture and full reliance on Tesla’s vision-based Full Self-Driving technology.
The Cybercab, envisioned as a sub-$30,000 autonomous two-seater for robotaxi fleets, represents Tesla’s bold pivot toward scalable autonomy and robotics.
Tesla fans and enthusiasts on X praised the imagery, with many expressing excitement over the visible progress toward deployment. While challenges remain, including software maturity, regulatory hurdles, and supply chain scaling, the increased factory activity underscores Tesla’s momentum in turning the Cybercab vision into reality.
As Giga Texas continues expanding and refining the manufacturing process of the Cybercab, the coming months will prove to be a pivotal time in determining how quickly this revolutionary vehicle reaches roads in the U.S. and internationally.
Tesla influencers argue company’s polarizing Full Self-Driving transfer decision
Tesla Semi’s latest adoptee will likely encourage more of the same
