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SpaceX scrubs Starhopper’s final Raptor-powered flight as Elon Musk talks “finicky” igniters
For unknown reasons, SpaceX’s Starhopper prototype suffered a hold just 0.8 seconds prior to its second planned flight test, a hold that was eventually followed by a decision to scrub the August 26th attempt and try again tomorrow, August 27th.
Starhopper is a full-scale, partial-height testbed for SpaceX’s next-generation Starship launch vehicle, serving more as a semi-mobile test stand for steel rockets and Raptor engines than an actual Starship prototype. The unusual vehicle took flight for the first time ever on July 25th, reaching an altitude of roughly 20m (65 ft) under the power of a single Raptor engine, capable of producing up to 200 tons (450,000 lbf) of thrust. That test also suffered a minor scrub on the 24th, followed by a successful flight one day later, a chapter that Starhopper may now mirror on its second attempted flight, a 150m (500 ft) hop.
Notably, SpaceX CEO Elon Musk took to Twitter just seconds after the rocket’s scheduled liftoff suffered a last-second hold to indicate that Raptor’s torch igniters were proving somewhat finicky relative to the chemical alternative used by SpaceX’s proven Merlin engines.
The CEO later confirmed that that comment was directly related to the 26th’s scrub, indicating that Raptor serial number 06 (SN06) needed to have its igniters inspected prior to a second hop test attempt, now scheduled to occur no earlier than 6pm EDT (22:00 UTC) on August 27th. The gist of the difficulties with Raptor’s igniter starts with the reason that SpaceX is attempting to integrate an entirely new form of ignition into the engine, replacing the methods successfully used over tens or even hundreds of thousands of seconds of firing with the company’s Merlin 1 and Merlin Vacuum engines.
Merlin 1D and MVacD both rely on a relatively simple, reliable, cheap, and easy method of chemical ignition, using a duo of pyrophoric materials known as triethylaluminum-triethylborane (TEA-TEB). When mixed, these materials immediately combust, generating an iconic green flash visible during Falcon 9 and Heavy launches, and thus producing the ‘spark’ needed to start Merlin engines.
Generally speaking, TEA-TEB is an excellent method of igniting rockets, even if it is more of a brute-force, inelegant solution than alternatives. It does, however, bring limitations: every single ignition requires a new ‘cartridge’ be expended, fundamentally limiting the number of times Merlin 1D (and Merlin Vacuum) engines can be ignited before and after liftoff.
This doesn’t even consider the fact that TEA-TEB are extremely complex chemical products that would be next to impossible to produce off of Earth, at least for the indefinite future.
To combat these downsides, SpaceX has designed Raptor with an entirely different method of ignition, known as torch ignition. Technically speaking, Raptor’s power, design, and methalox propellant combine to demand more than a relatively common solution, in which spark plugs are used to ignite an engine. Instead, Raptor uses those spark plugs to ignite its ignition sources, what CEO Elon Musk has described as full-up blow torches. Once ignited, those blow torches – likely miniature rocket engines using the same methane and oxygen fuel as Raptor – then ignite the engine’s methane and oxygen preburners before finally igniting those mixed, high-pressure gases in the combustion chamber.
In simple terms, the fact that Raptor is a full-flow staged-combustion (FFSC) engine means that the pressures it must operate under are extreme, verging on unprecedented in large-scale rocketry. Extremely high-pressure gases (on the order of 3,000-10,000+ psi or 200-700+ bar) are just as difficult to reliably ignite, especially if hypergolic solutions (i.e. TEA-TEB) are off the table.
To get an even ignition – critical to avoid burn-through, minor explosions, and even catastrophic engine failures – Raptor’s torch ignition may actually involve a 360-degree ring of spark plug-lit torches around the point of ignition, an undeniably complex solution.
However, as Musk notes, these significant, “finicky” challenges brought on by Raptor’s exotic ignition method are motivated by the potential benefits such a solution might bring. Relative to Merlin 1D’s TEA-TEB ignition, torch ignition – once optimized and matured into a reliable solution – will permit an almost unlimited number of Raptor ignitions before, during, and after flight.
Avoiding TEA-TEB and other complex chemical igniters also means that Starship will technically be able to launch to Mars or the Moon, perform injection and landing burns, maybe even hop around the surface, and still be able to return to Earth – all without resupply. Such a return voyage would still be predicated on the ability to generate the methane and oxygen propellant needed to fuel Starships, but – assuming that challenge can be solved – torch-lit Raptors would be ready for such a mission. In the event that, say, something like August 26th’s scrub happens to a Starship on Mars, the crew would also be able to get out, inspect Starship’s Raptors, and even replace faulty spark plugs if necessary.
Technically, one could bring lots of spare TEA-TEB cartridges and install those in space or after landing, but those cartridges are quite literally firebombs waiting to ignite, whereas spare spark plugs are entirely inert.
For now, we’ll have to wait for SpaceX technicians to get their eyes and hands-on Starhopper’s lone Raptor engine to verify that its ignition hardware is in good health. If all goes well, Starhopper will attempt its final flight test as early as August 27th.
Update (August 27th): Starhopper is reportedly set for a second attempted 150m (500 ft) flight test today, scheduled to occur no earlier than 5pm EDT (21:00 UTC) on August 27th. Stay tuned for SpaceX’s official Livestream!
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Tesla Cybercab skips the traditional paint shop entirely, marking an unorthodox process for coloring the fully autonomous vehicle. However, the decision was a smart one, as it slashed factory costs, floor space utilization, and complexity, since Tesla relied on specialized alloys and in-mold coloring.
Munro Live was given the opportunity to do a factory walkthrough with Tesla Vice President of Vehicle Engineering Lars Moravy, who explained and detailed how Cybercab production at Giga Texas eliminates one of the automotive manufacturing industry’s most expensive and space-hungry elements.
A conventional paint line can cost hundreds of millions of dollars and require a million man-hours to build. Moravy framed the choice around Tesla’s core rule: “Question the requirements: why do you need paint?”
🚨 Super cool quote from the Cybercab breakdown on the decision to avoid traditional paint:
“One of the most expensive parts of the factory is a paint line… a few hundred million dollars, a million man hours to build one… rule number one at Tesla, question the requirements. Why do you need paint?… the alloys we use in the castings… don’t oxidize and reduce strength over time.” -@larsmoravy
Model Y and Cybertruck bodies are fully coated and painted. On Cybercab, only the side pieces get the anti-corrosion dip coat, and there’s no paint shop at all, which helps cut factory floor space per car by about 50%.
— TESLARATI (@Teslarati) October 26, 2026
The structural answer lies in material selection. The aluminum alloys used in Cybercab’s front and rear castings do not oxidize and lose strength over time, the way many common automotive aluminum alloys do. Only the side modules, built around hot-stamped boron-steel door rings, receive an anti-corrosion e-coat, or dip coat. Front and rear modules skip coating altogether.
Model Y and Model 3 bodies, by contrast, are fully coated and painted.
Exterior colors come from the plastics shop, which Tesla engineers described as “our paint shop” for the Cybercab. Body panels are produced via reaction injection molding, referred to as RIM. Color is then mixed into a polyurethane resin at the mix head immediately before injection, so the panel emerges already colored with a Class-A surface.
Robots trim overflow to control sink marks and flow lines. The process avoids conventional spray-paint defects like orange peel and paint bleed. Scratches can still be repaired with compatible coatings that behave “basically like paint.” Because color is integral rather than a surface layer, shallow scratches do not expose a contrasting undercoat.
The secret behind Tesla’s Cybercab Gold goes well beyond just the color
Tesla has also explored related approaches, including in-mold lamination and painted films on stamped panels.
The manufacturing payoff is substantial because removing the paint shop, combined with the “unboxed” modular process that builds and tests front, rear, side, and center modules in parallel before a short final assembly, cuts factory floor space per vehicle by about 50 percent.
Final assembly itself uses only about 25 automated stations, far fewer than the typical Model Y line, and the overall line runs at about 78 percent automation, Moravy said. The approach also eliminates volatile organic compound emissions associated with traditional spray painting for these panels and shortens the coloring cycle from hours to minutes.
Cybercab’s paint strategy is clearly less about aesthetics than about systematically deleting capital-intensive, energy-heavy, and space-consuming steps once material science and process design make them unnecessary. It is a concrete example of Tesla applying first-principles questioning to one of the auto industry’s most entrenched factory requirements.
Investor's Corner
Tesla has a Cybercab problem nobody saw coming
Tesla’s Cybercab line now builds robotaxis faster than Tesla can deploy them, Lars Moravy says.
Tesla’s Cybercab line in Texas can now build the two seat robotaxi faster than the company can put it into service, according to Lars Moravy, Tesla’s Vice President of Vehicle Engineering. “We don’t run every day because the line can run so fast. It’s currently outpacing our deployments,” Moravy said in a new Cybercab deep dive from Munro Live. “So, it’s a bit of a race right now. Who’s going to go faster? Right now the manufacturing line’s ahead.”
Tesla’s official Robotaxi account shared a Cybercab analysis video on X on Monday, calling it a “Cybercab engineering deep dive.” Moravy’s comments go further than what he told analysts on the Q3 earnings call last week, when he said the Cybercab line’s listed capacity of more than 125,000 units a year undersells what it can actually run.
The tour shows where that speed comes from. Tesla’s unboxed process splits the Cybercab into front, rear, side and center modules that are built and tested on their own before they meet on a short final line. That final line has just 25 fully automated stations, which Tesla’s team estimated is a fifth to a tenth of what a Model Y needs. The full line is about 78% automated, the framing line is already at 100%, and the layout uses roughly 50% less floor space per vehicle. The stated goal is “100% automation in 10 second cycle time,” or one finished Cybercab every 10 seconds.
Tesla also deleted the paint shop. Only the side modules are coated, and the exterior panels get their color inside the molding machine. Engineers said the car is designed to run at least 500,000 miles, which matters for a vehicle that will spend most of its day carrying riders.
The battery got the same treatment. The Cybercab uses an 88S6P pack of 4680 cells in a steel enclosure, a first for Tesla, with each module potted separately so a single failed module can be swapped instead of the whole pack. Wireless battery management boards replace a wiring harness, and new contactors are fast enough to drop the pyro fuse entirely. Tesla’s battery director graded the pack an A minus, compared with a D for the Model Y structural pack and a B minus for Cybertruck. Up front, the drive unit runs an 11:1 gear ratio versus roughly 9:1 on most Teslas, since the Cybercab does not need a high top speed.
Cybercab engineering deep dive — Robotaxi (@robotaxi) October 26, 2026
The deployment side is now the bottleneck Moravy described. Tesla had more than 50 Cybercabs working the Formula 1 weekend in Austin, and Texas records show 463 Cybercabs registered. Tesla said on its earnings call that Cybercab service will launch in Dallas next month, and Moravy said the company is aiming to get Cybercabs to customers by the end of 2026. Every unit built so far has gone into Tesla’s own fleet since the line moved into volume production in April.
Munro Live also asked when it could get a Cybercab to tear down. Tesla’s answer: “Not yet.”
SpaceX’s Raptor engine family has steadily increased sea-level thrust while simultaneously reducing mass, turning iterative engineering gains into substantially higher performance for the Super Heavy booster. CEO Elon Musk shed more light on how powerful Raptor 4 will be, and it’s pretty crazy.
Raptor 1 delivered 185 metric tons of thrust at roughly 2,080 kilograms, while Raptor 2 raised that to 230 tons while cutting mass to about 1,630 kilograms. SpaceX data for Raptor 3 lists a target of 280 tons at 1,525 kilograms (with further reductions in associated vehicle hardware), while operational flight ratings have been cited near 250 tons.
This morning, Elon Musk stated that Raptor 4 is expected to reach 300 tons of sea-level thrust at roughly the same mass as Raptor 3. Across these versions, thrust has risen by more than 60 percent from the first engines while engine mass has fallen, producing a sharp improvement in thrust-to-weight ratio. This is a true testament to how great SpaceX engineering has been:
🚀 Elon says Raptor 4 will make 300 tons of thrust at sea level at roughly the same mass as Raptor 3.
How far Raptor has come:
Raptor 1: 185 tf, 2,080 kg
Raptor 2: 230 tf, 1,630 kg
Raptor 3: 250 tf, 1,525 kg
Raptor 4: 300 tf33 on Super Heavy = ~9,900 tf, nearly 3x Saturn V https://t.co/HQDswZhyvL
— TESLARATI (@Teslarati) October 26, 2026
With 33 engines on SuperHeavy, the jump from earlier versions to a 300-ton Raptor 4 would produce roughly 9,900 metric tons of total liftoff thrust, nearly three times the Saturn V’s approximately 3,400 metric tons from its five F-1 engines.
This is not just a larger number on a data sheet, either, as sea-level thrust is the force available the moment the vehicle leaves the pad. This is when it is heaviest and still deep in Earth’s gravity well and dense atmosphere.
Higher levels of sea-level thrust directly improves the initial thrust-to-weight ratio of the full stack. A higher ratio produces faster acceleration off the pad, which shortens the time the rocket has to spend fighting gravity, and gravity losses during the first minute or two of the flight are a major drain on total available delta-v. Every second shaved off of that early climb preserves more propellant energy for reaching orbital velocity or for carrying extra payload.
Because Super Heavy’s engine count is constrained by vehicle diameter and packing density, increasing thrust per engine is the most straightforward way to raise total liftoff performance without redesigning the booster structure or design.
The same-mass target for Raptor 4 is equally important. Holding engine mass roughly constant while raising thrust improves the engine’s own thrust-to-weight ratio and reduces the structural and propellant mass fraction that must be carried solely to support the engines.
Earlier Raptor iterations also simplified or eliminated extensive vehicle-side hardware such as heat shields. These gains compound: more force for less installed mass leaves additional capacity for propellant, payload, or operational margins such as engine-out capability.
For Starship’s architecture, the practical effects are large. Greater liftoff thrust supports heavier vehicles, larger propellant loads, and higher payloads to low Earth orbit, figures SpaceX has targeted in the 100-plus-ton reusable range. That capacity underpins orbital refueling, lunar missions, and eventual Mars cargo and crew flights.
Continued growth in sea-level thrust therefore tightens the gap between theoretical rocket performance and the high flight rates and reusability needed to make large-scale space transport practical.
Tesla Cybercab’s unorthodox paint process explained
Tesla has a Cybercab problem nobody saw coming
