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Stoke Space to build SpaceX Raptor engine’s first real competitor

Stoke Space has begun testing parts of an engine similar to SpaceX's famous Raptor.

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Seattle startup Stoke Space has revealed plans to develop an efficient rocket engine similar to the Raptors that power SpaceX’s Starship.

Formed in October 2019, Stoke Space secured its first significant round of funding – $9.1 million – less than three years ago. At that time, CEO and co-founder Andy Lapsa says that the startup had just five employees, no permanent workspace, and a “barren field” for a test site. Within 18 months, Stoke Space had turned that empty field into an impressive test facility, conducted numerous component tests, and assembled its first full-scale rocket engine – an exotic UFO-like device unlike any seen before.

It also raised another $65 million – enough funding to begin earnestly developing a potentially revolutionary rocket capable of launching more than 1.65 tons (~3600 lb) into orbit for less than half a million dollars. To realize that extremely ambitious goal, Stoke Space has taken the even more ambitious step of attempting to make the first rocket it develops fully reusable. Simultaneously, the company has incorporated several exotic technologies into that rocket, recently culminating in a surprise announcement that it will attempt to develop one of the most difficult types of engines to power that rocket’s booster stage.

Full-flow staged combustion

At the end of an extended interview and tour with YouTuber Tim Dodd (The Everyday Astronaut), CEO Andy Lapsa revealed that Stoke Space has decided to build a full-flow staged combustion (FFSC) engine for the first stage of its reusable rocket. FFSC is the most efficient type of combustion cycle available for a chemical bipropellant rocket engine, but it’s also the most difficult to develop.

A full-flow engine attempts to squeeze every possible ounce of performance out of the propellant it consumes. The most powerful and efficient chemical rocket engines must consume huge volumes of propellant in a short amount of time without destroying the launch vehicle they’re attached to. To create pressure and spin the pumps that are needed to feed that propellant into their main combustion chamber, engines often burn a small amount of propellant in a separate gas generator or preburner. Gas-generator engines vent that exhaust overboard, reducing efficiency but making for a much simpler design. Staged-combustion engines use preburners to create gas that pumps liquid propellant, and that exhaust gas is eventually injected into the main combustion chamber.

Full-flow staged combustion sets itself apart by having two separate pumps and preburners for oxidizer and fuel. Unlike simpler variants of staged combustion, FFSC engines turn all of their propellant into gas before injecting it into the combustion chamber. That hot gas increases the heat of combustion and the pressure inside the combustion chamber, ensuring that virtually all of the propellant that flows through the engine is combusted and turned into thrust as efficiently as possible. FFSC is exceptionally difficult because of the extra-high temperatures and pressures it requires, as well as the need for an oxygen-rich preburner and pump. In a high-pressure, hot-oxygen environment, virtually anything imaginable – including most metals – will spontaneously combust.

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Only complex custom-designed alloys can survive those conditions. SpaceX’s Raptor, the only FFSC engine that has ever flown, is especially difficult because it’s meant to be highly reusable. To be successful, Raptor will have to survive those conditions dozens or even hundreds of times in a row with little to no maintenance in between.

The first booster engine Stoke Space ever attempts to build will be a reusable full-flow staged combustion engine powered by liquid methane and liquid oxygen – essentially a smaller version of SpaceX’s Raptor. Stoke’s booster is otherwise familiar and features deployable landing legs like SpaceX’s Falcon boosters. Lapsa says it will likely also have grid fins.

Reusing the upper stage

In some ways, the upper stage of Stoke’s first rocket is even more ambitious. Powered by hydrogen and oxygen propellant, Stoke has designed a conical capsule-like upper stage with an integral fairing. The upper stage’s propulsion is exotic and unique. A large pump will feed propellant to up to 30 combustion chambers distributed around the rim of its heat shield. The exhaust coming from those 30 chambers will expand and partially push against the upper stage’s equally exotic metallic, liquid-cooled heat shield. That expansion against the heat shield improves the efficiency of the upper stage and means that its engine will technically be an aerospike.

Stoke has already begun testing a full-scale version of the upper stage’s UFO-like rocket engine with 15 combustion chambers. Since testing began in the second half of 2022, Stoke has completed dozens of static fires. Everyday Astronaut’s tour also revealed that the startup has made significant progress fabricating and assembling its first full-scale upper stage prototype – tanks, nosecone, heat shield, engine, and all.

Reminiscent of SpaceX’s Grasshopper and Starhopper campaigns, Stoke plans to conduct hop tests with that prototype if it makes it through qualification testing. On February 7th, Stoke also revealed that it’s begun testing a crucial component of its full-flow booster engine. All told, Stoke Space is making progress at a remarkable pace and continues to tackle the hardest problems. The startup has also avoided widely publicizing any specific deadlines, instead choosing to let hardware and tangible results speak for themselves. Only time will tell if that approach pays off, but Stoke is off to an exceptionally impressive start in an industry full of impressive rocket startups.

Eric Ralph is Teslarati's senior spaceflight reporter and has been covering the industry in some capacity for almost half a decade, largely spurred in 2016 by a trip to Mexico to watch Elon Musk reveal SpaceX's plans for Mars in person. Aside from spreading interest and excitement about spaceflight far and wide, his primary goal is to cover humanity's ongoing efforts to expand beyond Earth to the Moon, Mars, and elsewhere.

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Elon Musk

Elon Musk says SpaceX would not exist if this crucial early launch failed

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Credit: SpaceX

Elon Musk recently restated a fact that still defines SpaceX’s origin story: if Falcon 1’s fourth launch had failed, the company would not exist. The comment answered a reminder that after three consecutive losses, SpaceX had money for only one more attempt.

On X, Peter Diamandis said that the present-day acknowledgement of SpaceX’s success does not discount the rough start the company had. “Almost nobody remembers that Elon’s first rocket failed three times, and there was money for exactly only one more attempt.”

Musk said, “If the 4th launch had failed, SpaceX would not exist.”

In late 2008, the firm was nearly out of cash. Another failure would have ended payroll, closed the Hawthorne factory, and left the Falcon 9 and Dragon programs as unfinished drawings.

The first flight lifted off from Omelek Island on 24 March 2006. Thirty-three seconds later, a corroded aluminum fitting on a fuel line leaked. Kerosene ignited around the Merlin engine, control was lost, and the vehicle came apart. The small DARPA payload, FalconSAT-2, survived the short flight only to land on a storage shed near the pad. Investigators later traced the fitting to a materials mix-up that should never have reached the rocket.

Flight 2, on 21 March 2007, looked far better at first. The first stage burned cleanly and handed off to the Kestrel-powered upper stage. The vehicle crossed 100 kilometers and reached a peak of about 289 kilometers. Then propellant slosh in the second-stage tank started a circular coning motion that grew until the engine shut down. Telemetry faded as the stage tumbled, and SpaceX had reached space but not orbit. Over the next year, the team redesigned everything from the ground up, including tanks, baffles, and the new regeneratively cooled Merlin 1C.

That engine flew on Flight 3 on 2 August 2008. The first stage performed almost perfectly and reached 217 kilometers. After main-engine cutoff, leftover fuel in the cooling channels produced a faint residual thrust, roughly 10 pounds per square inch of chamber pressure. On a Texas test stand, the effect was invisible beneath ambient air pressure. In vacuum it was enough to push the spent first stage back into the second stage after separation. The stages collided, the upper stage spun, and the mission was lost. Musk later said a slightly longer delay before staging would have saved the flight.

Six weeks later, the team assembled Flight 4 from remaining parts and flew it on 28 September 2008 at 23:15 UTC. The payload was Ratsat, a 165-kilogram aluminum mass simulator built in-house. Staging was delayed so residual thrust could decay. The Kestrel ignited, the fairing split away, and nine and a half minutes after liftoff the vehicle was in orbit. After a coast, the second stage restarted, settling into a 621-by-643-kilometer path at 9.35 degrees inclination. Falcon 1 became the first privately developed liquid-fueled rocket to reach Earth orbit. Musk called the insertion “middle of the bull’s-eye.”

SpaceX restores a Falcon 1 rocket for 10th anniversary of first launch success

That success unlocked NASA’s Commercial Resupply Services award later that year. Without it, there would have been no Falcon 9, no reusable first stages, and no Dragon cargo or crew flights to the International Space Station. Launch prices would have remained far higher. Starlink’s constellation would not exist; broadband from low Earth orbit would still be a paper concept.

Ride-share markets, high launch cadence, and the current pace of lunar and Mars hardware would be years behind. Communications, Earth observation, and the cost of putting anything into space would look more like the 2000s than the 2020s.

One extra second of residual thrust in August 2008 would have written a different decade.

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Tesla surges Robotaxi fleet ahead of Cybercab launch event

Tesla’s unsupervised robotaxi fleet quietly grew sevenfold in three weeks just before Cybercab Day arrives.

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Tesla’s unsupervised Robotaxi fleet has grown far faster than the public numbers suggested, and the timing lines up with the company’s biggest autonomy showcase yet. According to data compiled by the crowdsourced Robotaxi Tracker, Tesla now has nearly 200 vehicles operating without a safety monitor across Austin, Dallas and Houston, yielding a roughly 7X increase in about three weeks.

The jump lands four days before this week’s Tesla Cybercab launch event in Austin, where the company plans to show off its purpose-built, two-seat robotaxi with no steering wheel or pedals in a live commercial setting for the first time. Stick with us on X and Facebook for live reporting from the event.

The strategic logic is straightforward. Tesla has spent the past year scaling Robotaxi in small, deliberate steps, first widening geofences, then extending operating hours, then quietly growing fleet size, usually with little advance notice. Ashok Elluswamy told investors on the Q2 earnings call that the program had logged more than 380,000 unsupervised miles with zero notable incidents, a safety record the company has leaned on to justify moving slowly. Critics have used the flip side of that caution, a fleet that appeared stuck around two dozen vehicles for months, as evidence that Tesla’s driverless ambitions were outrunning its actual deployment.

A fleet quietly scaling to nearly 200 vehicles right before Cybercab Day undercuts that argument without Tesla having to say anything about it directly. It also sets up the event to do double duty. Rather than simply introducing new hardware, Tesla can point to an operating base of unsupervised Model Ys already running at meaningful scale, then argue the Cybercab, which uses the same underlying Full Self-Driving stack according to earlier coverage of the fleet’s software upgrades, is a natural next steps. Tesla has separately been registering the two-seat Cybercabs with Texas regulators this week, with the count climbing from seven to 45 in a matter of days.

The two ramps, one in software-driven Model Y deployment and one in physical Cybercab registrations, are happening in parallel rather than in sequence. That suggests Tesla wants Thursday’s event to land as proof that the robotaxi business is already running at scale, not just a reveal of a new vehicle shape. Whether the unsupervised numbers hold up once Cybercabs start mixing into the same fleet is the detail worth watching once the event wraps.

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Cybertruck

Tesla Cybertruck windshield protection just got cheaper

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Credit: Tesla

Tesla is lowering the monthly price of its Cybertruck Windshield Protection Plan from $35 to $25. The new rate will apply to the first payment on or after October 1, 2026. Tesla has told subscribers that all other benefits stay the same.

The plan covers unlimited repairs for chips and minor cracks on the front windshield. It also includes one full replacement every 12 months at no extra charge. Additional replacements in the same year carry a $100 deductible. Service is performed with Tesla glass and camera calibration, which matters because Autopilot and Full Self-Driving rely on those lenses behind the windshield.

There is no long-term contract. Coverage applies only to the front glass and does not include collision, vandalism, or weather damage.

The Cybertruck’s large, complex windshield has been more expensive to replace than glass on Tesla’s cars, which is why the pickup started at a higher subscription price. The $10 monthly cut reduces the annual cost from $420 to $300. Tesla has not publicly explained the change. The timing coincides with a year of claims data after the plan was extended to the Cybertruck.

Tesla sells several related protection products as monthly subscriptions through the Tesla app. The Windshield Protection Plan is also offered on other models. Model 3 and Model Y currently cost $16 a month. Those passenger-car rates are unchanged in the latest Cybertruck notice.

The Wheel and Tire Protection Plan covers road-hazard damage such as potholes, nails, and debris. Repairs are unlimited. Each wheel or tire replacement appointment has a $25 deductible. Pricing varies by model and whether the vehicle is a Performance version. Tesla is raising some of those rates on the same October 1 date.

Reported examples include Model 3 Performance moving from $16 to $24 and Model Y Performance from $20 to $24. Cybertruck wheel-and-tire coverage has been listed at $20 a month for the standard configuration.

A separate Luxe Package bundles four years of windshield coverage, wheel-and-tire coverage, and recommended maintenance on certain new Model S, Model X, and Cyberbeast orders, although the Model S and X are now defunct.

Tesla also offers an Extended Service Agreement after the basic vehicle warranty ends. That product covers many Tesla-manufactured parts rather than glass or tires. Together, the plans give owners a menu of targeted, cancel-anytime coverage instead of relying only on auto insurance.

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