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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.
Tesla is continuing to refine and improve its Robotaxi program from A to Z, and it is now going to make some sweeping changes to the smartphone app portion of the suite.
The company is aiming to make some sweeping changes with the release of Robotaxi app version 26.4.5, which was recently decompiled by Tesla App Updates on X. The update reveals significant new code, focused on remote operations, safety protocols, and seamless autonomous ride-hailing.
These improvements evidently signal Tesla’s preparations for scaling unsupervised Cybercab deployments, particularly the steering wheel-less variants spotted in production. The enhancements emphasize providing a reliable experience that gives passengers support when needed, along with operational efficiency.
Version 26.4.5 of the Robotaxi app has been de-compiled and we’ve got some interesting things added this update (https://t.co/jInbED7fOv):
– Remote Operator Voice Calls 📞
– Proactive Remote Assistance 🤖
– Manual Override + Remote Start for wheel-less Cybercabs 🎮
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— Tesla App Updates (iOS) (@Tesla_App_iOS) May 16, 2026
Remote Operator Voice Calls
One standout addition is support for remote operator voice calls. The app now includes a dedicated native voice-communication system linking passengers directly to Tesla teleoperators via the vehicle’s cabin microphone and speakers.
This feature allows real-time assistance during rides, addressing issues like navigation questions or comfort adjustments without disrupting the autonomous journey. It builds on existing support protocols, making human intervention more accessible and intuitive.
Proactive Remote Assistance
The update introduces proactive remote assistance capabilities. Rather than waiting for passenger-initiated requests, the system can anticipate and offer help based on monitored conditions.
This might include something like suggesting route changes, climate adjustments, or addressing potential delays. By integrating AI-driven monitoring with human oversight, Tesla aims to deliver a smoother, more attentive experience that exceeds traditional ride-sharing services.
Manual Override and Remote Start for Steering Wheel-less Cybercabs
A key highlight for the wheel-less Cybercab fleet is manual override plus remote start functionality. Fleet operators and technicians can now temporarily take control or remotely start vehicles lacking steering wheels. This is crucial for lower-speed maneuvers, such as getting vehicles from tight parking situations or even performing maintenance.
Controls are strictly limited for safety–typically to speeds under 2 MPH–ensuring these interventions remain emergency measures only.
Tesla is adding a secure “Enable Manual Drive” mode that will allow those fleet operators or others to take control temporarily.
Additionally, a Remote Start feature, which authorizes an empty vehicle to begin a driverless ride alone.
Ride-Hailing and Dispatch Features
Ride dispatch has been enhanced with soft-matching and multi-stop support. The app can intelligently pair riders with available Cybercabs while accommodating multiple destinations in a single trip.
This optimizes fleet utilization, reduces wait times, and improves efficiency for shared rides. Soft-matching likely considers factors like proximity, rider preferences, and vehicle availability for better user satisfaction.
Rider-Cabin Sync, Real-Time Routing
New synchronization tools allow the rider’s app to mirror and control cabin settings like seating, climate, and entertainment directly from their phone. Real-time routing updates adapt dynamically to traffic or road conditions, while dynamic safety monitoring continuously assesses the environment.
The app can now push updates directly to the main screen, enabling Center Display Control. Additionally, there is a dedicated navigation protocol sharing the exact coordinates of road closures and construction, which could prevent the car from getting stuck and needing manual override.
These features create a cohesive, responsive experience where the vehicle and app work in harmony.
Kill Switch
A high-security command lets Tesla completely freeze a vehicle’s ability to drive. This would take the vehicle out of the Robotaxi fleet for any reason Tesla sees fit, and would not allow it to be put into gear even with the correct equipment, like valid keys.
Elon Musk
SpaceX just forced Verizon, AT&T and T-Mobile to team up for the first time in history
AT&T, T-Mobile, and Verizon just joined forces for one reason: Starlink is winning.
America’s three largest wireless carriers, AT&T, T-Mobile, and Verizon, announced on On May 14, 2026 that they had agreed in principle to form a joint venture aimed at pooling their spectrum resources to expand satellite-based direct-to-device (D2D) connectivity across the United States in what can be seen as a direct response to SpaceX’s Starlink initiative. D2D, in plain terms, is technology that lets a standard smartphone connect directly to a satellite in orbit, the same way it connects to a cell tower, with no extra hardware required.
The alliance is widely seen as a means to slow Starlink’s rapid expansion in the satellite internet and mobile markets. SpaceX’s Starlink Mobile service launched commercially in July 2025 through a partnership with T-Mobile, starting with messaging before expanding to broadband data. SpaceX secured access to valuable wireless spectrum through its $17 billion deal with EchoStar, paving the way for significantly faster satellite-to-phone speeds.
SpaceX was not shy about its reaction. SpaceX president and COO Gwynne Shotwell responded on X: “Weeeelllll, I guess Starlink Mobile is doing something right! It’s David and Goliath (X3) all over again — I’m bettin’ on David.” SpaceX’s VP of Satellite Policy David Goldman went further, flagging potential antitrust concerns and asking whether the DOJ would even allow three dominant competitors to coordinate in a market where a new rival is actively entering.
Weeeelllll, I guess @Starlink Mobile is doing something right! It’s David and Goliath (X3) all over again — I’m bettin’ on David 🙂 https://t.co/5GzS752mxL
— Gwynne Shotwell (@Gwynne_Shotwell) May 14, 2026
Financial analysts at LightShed Partners were blunt, saying the announcement showed the three carriers are “nervous,” and pointed to the timing: “You announce an agreement in principle when the point is the announcement, not the deal. The timing, weeks ahead of the SpaceX roadshow, was the point.”
As Teslarati reported, SpaceX’s next generation Starlink V2 satellites will deliver up to 100 times the data density of the current system, with custom silicon and phased array antennas enabling around 20 times the throughput of the first generation. The carriers’ JV, which has no definitive agreement, no financial structure, and no deployment timeline yet, will need to move quickly to matter.
Elon Musk’s SpaceX is targeting a Nasdaq listing as early as June 12, aiming for what would be the largest IPO in history. With Starlink now serving over 9 million subscribers across 155 countries, holding 59 carrier partnerships globally, and now powering Air Force One, the carriers’ joint venture announcement landed at exactly the wrong time to look like anything other than a defensive move.
Tesla just raised Model Y prices for the first time in two years, with the largest increase being $1,000.
The move signals shifting dynamics in the competitive electric vehicle market as the company continues to work on balancing demand, profitability, and accessibility.
The new pricing affects premium trims while leaving entry-level options unchanged. The Model Y Premium Rear-Wheel Drive (RWD) now starts at $45,990, a $1,000 increase.
The Model Y Premium All-Wheel Drive (AWD)—previously referred to in the post as simply “Model Y AWD”—rises to $49,990, also up $1,000. The top-tier Model Y Performance sees a more modest $500 bump, bringing its starting price to $57,990.
Tesla Model Y prices just went up:
New prices:
🚗 Model Y Premium RWD: $45,990 – up $1,000
🚗 Model Y AWD: $49,990 – up $1,000
🚗 Model Y Performance: $57,990 – up $500 https://t.co/e4GhQ0tj4H pic.twitter.com/TCWqr3oqiV— TESLARATI (@Teslarati) May 16, 2026
Base models remain untouched to preserve affordability. The entry-level Model Y RWD holds steady at $39,990, and the base Model Y AWD stays at $41,990. This selective approach keeps the crossover accessible for budget-conscious buyers while extracting more revenue from higher-margin configurations.
After years of aggressive price cuts to stimulate volume amid slowing EV adoption and rising competition from rivals like BYD, Ford, and GM, Tesla appears confident in underlying demand. Recent lineup refreshes for the 2026 Model Y, including refreshed styling and efficiency gains, have helped maintain its status as America’s best-selling EV.
By protecting base prices, Tesla avoids alienating price-sensitive customers while improving margins on the more popular variants.
Tesla Model Y ownership review after six months: What I love and what I don’t
For consumers, the changes are relatively modest—under 3% on affected trims—and still position the Model Y competitively against gas-powered SUVs in the same class. Federal tax credits and potential state incentives may further offset costs for eligible buyers.
This marks a subtle but notable shift from the deep discounting era that defined much of 2024 and 2025. As the EV market matures into 2026, Tesla’s pricing strategy will be closely watched for clues about production ramps, new variants like the rumored longer-wheelbase Model Y, and broader profitability goals.
In short, today’s adjustment reflects a company that remains dominant yet pragmatic—willing to test higher pricing where demand supports it. It is unlikely to deter consumers from choosing other options.
Tesla is making sweeping improvements to Robotaxi
Starship V3 is here putting SpaceX closer to Mars than it has ever been
