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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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3 years ago

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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.

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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.

SpaceX’s Raptor engine.
A single-Raptor static fire.
The 33-engine base of Starship’s first stage.
Stoke’s fully-reusable rocket.
The booster appears to have seven FFSC engines.
The upper stage has a single engine with 30 combustion chambers.

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.

The upper stage prepares for reentry.
The upper stage separates from the booster.
A render of the upper stage heat shield.
The upper stage touches down.
Individual Stoke thrusters.
A 15-chamber static fire.
A prototype of the upper stage heat shield and engine.
A prototype of the upper stage tanks. (Everyday Astronaut)

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.

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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

Tesla Board Chair discusses what is being done to protect CEO Elon Musk

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1 hour ago

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September 12, 2025

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Credit: xAI

Tesla Board Chair Robyn Denholm met with Bloomberg this morning to discuss a variety of topics, but perhaps one of the most interesting was her comments on what is being done to protect company CEO Elon Musk.

After the assassination of right-wing political commentator Charlie Kirk this week, there have been concerns about Musk’s safety, as well as that of other high-profile business leaders and political figures.

Earlier this week, Musk said himself that his security detail would be increased significantly following Kirk’s death, a move that many investors and fans of the company had requested because of political violence.

Elon Musk assures Tesla investors he will enhance his security detail

“Definitely need to enhance security,” Musk said. Tesla spent $3.3 million on Musk’s security in 2024 and January and February 2025. For reference, Meta spent over $27 million on Mark Zuckerberg’s security last year, which is higher than any other tech CEO.

During Denholm’s appearance on Bloomberg TV earlier today, she stated that the company has been focused on Musk’s security detail for “many years,” especially considering he is one of the richest people on Earth and holds an incredible amount of influence.

“It is something that we take very seriously; he takes it very seriously as well. So, again, from a board perspective, it is something we’ve discussed at length,” Denholm said.

Denholm added that she believes “there is not anyone in a boardroom that is not touched by what has happened with Charlie Kirk.”

Although Musk’s political involvement has toned down significantly in the past, he still has enemies, especially based on groups that oppose him and the company specifically. Based on this week’s events, it feels that increased security is a necessary expense Tesla must account for.

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Investor's Corner

Tesla bear turns bullish for two reasons as stock continues boost

“I think from a trading perspective, it looks very interesting,” Nathan said, citing numerous signs of strength, such as holding its 200-day moving average and holding against its resistance level.

Published

5 hours ago

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September 12, 2025

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Credit: Tesla Manufacturing

A Tesla bear is changing his tune, turning bullish for two reasons as the company’s stock has continued to get a boost over the past month.

Dan Nathan, a notorious skeptic of Tesla shares, said he is changing his tune, at least in the short term, on the company’s stock because of “technicals and sentiment,” believing the company is on track for a strong Q3, but also an investment story that will slowly veer away from its automotive business.

“I think from a trading perspective, it looks very interesting,” Nathan said, citing numerous signs of strength, such as holding its 200-day moving average and holding against its resistance level.

He also said he believes a rally for the stock could continue as it heads into the end of the quarter, especially as the $7,500 electric vehicle tax credit is coming to an end at the end of the month.

With that being said, he believes the consensus for Q3 deliveries is “probably low,” as he believes Wall Street is likely underestimating what Tesla will bring to the table on October 1 or 2 when it reports numbers for the quarter.

Tesla shares are already up over five percent today, with gains exceeding nine percent over the past five trading days, and more than fourteen percent in the past month.

While some analysts are looking at the performance of other Mag 7 stocks, movement on rates from the Federal Reserve, and other broader market factors as reasoning for Tesla’s strong performance, it appears some movement could be related to the company’s recent developments instead.

Over the past week, Tesla has made some strides in its Robotaxi program, including a new license to test the platform in the State of Nevada, which we reported on.

Tesla lands regulatory green light for Robotaxi testing in new state

Additionally, the company is riding the tails of the end of the EV tax credit, as inventory, both new and used, is running extremely low, generally speaking. Many markets do not have any vehicles to purchase as of right now, making delivery by September 30 extremely difficult.

However, there has been some adjustments to the guidelines by the IRS, which can be read here:

Tesla set to win big after IRS adjusts EV tax credit rules

Tesla is trading at around $389 at 10:56 a.m. on the East Coast.

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News

Tesla lands regulatory green light for Robotaxi testing in new state

This will be the third state in total where Tesla is operating Robotaxi, following Austin and California.

Published

1 day ago

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September 11, 2025

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Credit: Tesla

Tesla has landed a regulatory green light to test its Robotaxi platform in a new state, less than three months after the ride-hailing service launched in Texas.

Tesla first launched its driverless Robotaxi suite in Austin, Texas, back on June 22. Initially offering rides to a small group of people, Tesla kept things limited, but this was not to be the mentality for very long.

It continued to expand the rider population, the service area, and the vehicle fleet in Austin.

The company also launched rides in the Bay Area, but it does use a person in the driver’s seat to maintain safety. In Austin, the “Safety Monitor” is present in the passenger’s seat during local rides, and in the driver’s seat for routes that involve highway driving.

Tesla is currently testing the Robotaxi platform in other states. We reported that it was testing in Tempe, Arizona, as validation vehicles are traveling around the city in preparation for Robotaxi.

Tesla looks to make a big splash with Robotaxi in a new market

Tesla is also hoping to launch in Florida and New York, as job postings have shown the company’s intention to operate there.

However, it appears it will launch in Nevada before those states, as the company submitted its application to obtain a Testing Registry certification on September 3. It was processed by the state’s Department of Motor Vehicles Office of Business Licensing on September 10.

It will then need to self-certify for operations, essentially meaning they will need to comply with various state requirements.

This will be the third state in total where Tesla is operating Robotaxi, following Austin and California.

CEO Elon Musk has stated that he believes Robotaxi will be available to at least half of the U.S. population by the end of the year. Geographically, Tesla will need to make incredible strides over the final four months of the year to achieve this.

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