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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 Scienceâ„¢ 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.
Lucid CEO Silvio Napoli responded to rumors of an imminent bankruptcy that was reportedly being mulled after a report stated the automaker was working with the firm AlixPartners to iron out its next steps.
The company felt a massive loss on Wall Street yesterday, as the report essentially pushed the stock down as much as 55 percent on Tuesday.
The report, published initially by Eletric-Vehicles.com, claimed Lucid was essentially in dire straits and was told by AlixPartners, a commonly used restructuring advisor, to either take shares private or file for Chapter 11 bankruptcy protection.
Lucid’s head of Communications, Nick Twork, immediately challenged the report and stated the company “has sufficient liquidity to carry its operations well into next year.”
Now, the company’s CEO is chiming in as well, stating that the report is “so far from the facts that they require a direct response.”
Napoli said:
“Lucid is not considering bankruptcy or a transaction to take the company private. Those reports are false. The Board did not explore either scenario. Period.
As disclosed in our most recent quarterly filing, Lucid has sufficient liquidity to fund its operations well into next year.
We work with outside advisors to improve operational performance and execution. They are not advising Lucid on a take-private transaction or bankruptcy, and any suggestion that they have recommended either course of action to management or the Board is false.
My priority is clear: turn this company around. That is where the leadership team and I are focused.
I look forward to providing a full update during our quarterly earnings call on August 4th.”
🚨 Lucid CEO Silvio Napoli calls rumors of financial issues “so far from the facts that they require a direct response.”
Read his full remarks here: https://t.co/t3Pg1NHvzy pic.twitter.com/LvHUPhO4Qf
— TESLARATI (@Teslarati) July 15, 2026
It seems pretty clear that Lucid is confident things will be okay, and, to be honest, they should not have much to worry about, especially considering the company has been backed by the Saudi Public Investment Fund (PIF) for years. It has solid financial backing, and its sales, while weak, are pretty much right on par with a company of this age.
Lucid also sent a Cease & Desist letter to the publication for their report.
Lucid shares have rebounded nicely and are up nearly 21 percent at the time of publication. As soon as the company dispelled the rumors of bankruptcy yesterday, the stock began to climb back toward more reasonable levels.
Tesla has once again demonstrated strong customer focus by swiftly addressing and fully refunding a bizarre Supercharger pricing glitch that affected drivers in Atlantic Canada.
The issue surfaced earlier this month when the Tesla app began displaying dramatically inflated per-minute charging rates at stations in Prince Edward Island and parts of New Brunswick.
One widely shared screenshot from a Charlottetown, PEI Supercharger showed rates reaching ridiculous levels: $6.00 per minute for the 180-250 kW tier, along with $3.57/min for 100-180 kW and $2.29/min for 60-100 kW.
Correct pricing will be going live at midnight tonight. All fees since July 2nd 2026 will be waived.
— Tesla Charging (@TeslaCharging) July 13, 2026
These figures were several times higher than normal Supercharger pricing in the region.
To put the error in perspective, charging at the highest incorrect rate would have been shockingly expensive.
At 250 kW, a common charging speed at Superchargers, a vehicle pulls roughly 4.17 kWh per minute. Under the glitch, a driver spending just 10 minutes at peak power would face a $60 bill. A typical 20- to 30-minute session to add meaningful range could have cost $120 to $180 or more, before any congestion fees.
Tesla gets another layer of gamification with Free Supercharging on the line
By comparison, standard Canadian Supercharger rates usually fall between $0.25 and $0.60 per kWh, making a similar session cost roughly $15–$40. The erroneous per-minute structure, combined with the inflated numbers, turned what should be a convenient stop into a potential financial shock.
The glitch appears to have started sometime around early July, and quickly drew attention on social media as owners questioned whether Tesla had implemented steep hidden increases. Some drivers even reported seeing $0 charges in their history, indicating broader billing confusion.
Tesla’s official Charging account on X stated that correct pricing would roll out at midnight on July 13, so the fix is already in effect. More importantly, the company announced it would waive all fees for every Supercharger session since July 2. This blanket waiver covers the entire affected period without requiring users to file individual claims, with automated refunds expected soon. The decision affects stations in PEI and nearby areas in New Brunswick and Nova Scotia.
It’s a classy move, and rather than issuing partial credits or forcing owners to submit support tickets, Tesla simply absorbed the cost of the system error and made drivers whole. In an industry where hidden fees and bill disputes are common, Tesla’s proactive, no-questions-asked approach reinforces owner trust and highlights the company’s commitment to service excellence.
The incident, while disruptive for a short time, ultimately showcases Tesla’s ability to own mistakes and prioritize customer satisfaction. Atlantic Canada Tesla owners can now charge with confidence again, knowing the company has their back when technology glitches occur.
In an era of complex EV billing, such transparency and generosity are refreshing and set a positive example for the industry.
SpaceX’s Starlink has launched its latest residential hardware kit: the V5. Designed for reliable high-speed internet, the new terminal represents a significant leap forward in user equipment.
The next generation Starlink Kit is designed to deliver reliable, high-speed home internet. Starlink V5 has a smaller form factor and lightweight design with greater power efficiency than the Starlink V4.
With speeds up to 375+ Mbps, Starlink V5 delivers seamless connectivity… pic.twitter.com/0dorU6n0oD
— Starlink (@Starlink) July 14, 2026
The new V5 Starlink kit features a dramatically smaller and lighter form factor, measuring approximately 384 mm x 306 mm x 34 mm and weighing just 1.1 kg, which is less than half the weight of the previous V4 model, which was 2.9 kg.
This compact design makes installation easier and more versatile, whether mounted on a roof, pole, or even integrated with a pipe adapter. An integrated LED light aids setup in low-light conditions.
Power efficiency sees major gains too. The V5 draws only 35-50W, reducing energy consumption and making it ideal for off-grid or solar-powered setups. Despite its smaller size, performance remains robust. Starlink claims peak speeds of 375+ Mbps, supported by a new Wi-Fi 6 Router Mini that covers up to 2,200 square feet and connects up to 235 devices simultaneously.
The kit maintains strong signal reliability in diverse environments, from urban rooftops to remote rural areas, as demonstrated in the promo footage released by SpaceX, showing seamless operation under cloudy skies.
These improvements expand suitable applications considerably. Households can enjoy lag-free 4K streaming, smooth video conferencing, online gaming, and smart home device management without interruption. The V5’s efficiency and portability also benefit RVs, small businesses, and temporary installations in disaster-recovery zones where quick deployment is critical. Its lightweight build lowers shipping costs and simplifies user handling compared to bulkier predecessors.
Starlink’s Broader Impact on Global Internet Connectivity
Since SpaceX began launching Starlink satellites in 2019, the constellation has grown rapidly. By mid-2026, over 10,400 satellites orbit Earth, with thousands more deployed annually. This massive low-Earth-orbit network delivers broadband to approximately 160 countries and territories, reaching millions of users who previously lacked reliable internet access.
Starlink plays a vital role in bridging the digital divide. It provides essential connectivity to remote communities, maritime vessels, airlines, and regions affected by natural disasters or infrastructure gaps. By combining advanced satellite technology with iterative hardware upgrades like the V5 kit, SpaceX continues to push the boundaries of global internet access, fostering education, economic opportunity, and emergency response capabilities worldwide.
As production ramps up, the V5 promises to make high-performance internet even more accessible to users everywhere.
Elon Musk’s Texas ranch to showcase the lifelong work that changed the world
Lucid CEO dispels any rumors of bankruptcy: ‘So far from the facts’
