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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 will give ‘every kid in America’ a SpaceX share in 2027

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Credit: Grok Imagine

Elon Musk said he is planning to give “every one of his SpaceX shares to every kid in America” in 2027, stating that “this will be the first of many.”

SpaceX went public earlier this year, and its stock price has been relatively stable since leveling off shortly after its IPO. Based on its current price, it’s a gift of just over $10 billion to children across the United States.

It appears to be closely related to President Donald Trump’s bank accounts for children, which were set up earlier this year as Trump Accounts.

Just hours earlier, Anthropic had announced the establishment of its Anthropic Public Benefit Fund, “a new wholly-owned entity dedicated entirely to public benefit.” Musk responded by stating he recommended “giving the shares directly to the public,” and that he would be doing it that way.

Just a little bit later, Musk said children across the U.S. would be getting a share from him:

There are roughly 70 million children, meaning someone under the age of 18, in the United States, according to the Federal Interagency Forum on Child and Family Statistics. Musk’s ownership of SpaceX stock shows he has around 849 million Class A shares of SpaceX stock, according to filings with the SEC.

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Elon Musk reveals why Boring Co’s biggest East Coast project never happened

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(Credit: The Boring Company)

Elon Musk revealed in a post on X that “Permits were impossible to get,” explaining the fate of The Boring Company’s most ambitious East Coast proposal.

The comment responded to a query about what became of his July 20, 2017 announcement that he had “just received verbal govt approval” for an underground Hyperloop connecting New York City, Philadelphia, Baltimore, and Washington, D.C., capable of carrying passengers from the Big Apple to the Nation’s Capital in just 29 minutes.

The Boring Company receives verbal ‘approval’ to build NY to DC Hyperloop tunnel

The 2017 post, which envisioned city-center stations and multiple elevators in each city, sparked immediate scrutiny. Local and state officials in New York, Philadelphia, Baltimore, and D.C. said they had no knowledge of any approval. A White House spokesperson confirmed only “promising conversations” about the transformative infrastructure.

Musk clarified shortly after that there was “still a lot of work” to do for formal approvals.

Limited progress followed, as Maryland Governor Larry Hogan’s administration issued a conditional utility permit and supported work near Fort Meade. In 2018, Washington, D.C., granted a preliminary permit for site preparation and excavation on a vacant lot at 53 New York Ave. NE in the NoMa neighborhood, which The Boring Company said could become a station.

A draft environmental assessment for a D.C.-Baltimore segment was released in 2019. Yet, by April 2021, the company had removed the project from its website, and the Federal Highway Administration reported receiving no indication of further interest. Communication with Maryland officials had ceased.

The full corridor would have required coordination among the District of Columbia, Maryland, Pennsylvania, New York, the Federal Highway Administration, the Army Corps of Engineers, the National Park Service, and other agencies.

Environmental reviews under the National Environmental Policy Act, utility clearances, and approvals for novel infrastructure added to the overall complexity of the project and its approval.

Speculation on the permitting barriers centers around a few factors, but a multi-state, multi-level route involving unproven high-speed vacuum-tube technology inherently triggers exhaustive safety, environmental, and engineering reviews that can stretch for years, even for conventional projects.

There are also other elements, of course, like officials who may face political exposure if a privately funded, untested system encountered anything such as cost overruns, delays, or safety issues. On the outset of this project, there were limited things such as engineering plans or demonstrated technology maturity, which also added to the potential skepticism.

The East Coast vision for Boring Co., once framed as a privately funded revolution that could reshape Northeast travel, quietly ended without construction of the promised network. Musk’s recent statement frames the outcome as a regulatory impasse, unfortunate but not unexpected.

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Tesla CEO Elon Musk reminds everyone about Roadster’s true meaning

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Elon Musk addresses the crowd next to the new Tesla Roadster, which Tesla offers in Performance, Thrust and Rocket versions. (Image: Tesla/X)
Elon Musk addresses the crowd next to the new Tesla Roadster, which Tesla offers in Performance, Thrust and Rocket versions. (Image: Tesla/X)

Tesla CEO Elon Musk took to his social media platform X on Sunday to remind everyone that the Roadster’s true meaning is not about company growth or adding dollars to shareholders’ pockets. Sometimes, you just do things because you can.

Following the Roadster’s epic unveiling event last Thursday, skeptics and critics of the company or the project itself came out to say that the vehicle is a pointless project because it is not geared toward growing the company, delivering supreme margins for profitability, nor does it contribute to the big picture of Artificial/Super Intelligence.

But that’s just the thing: Roadster is not meant to be some shareholder dream; it’s meant to be a vehicle that people buy just because it is something awesome, unique, and the first of its kind.

Tesla Roadster: Three configs, one can fly, 0-60 in 0.8 seconds

Musk had to remind those who are skeptical about the Roadster’s importance to the company mission that while it is not a major contributor to Tesla’s long-term goals, it is something that is being built just because it can be:

“Optimus and Cybercab will be the vast majority of Tesla’s value. The only things that will scale to incredible size (K2 and beyond) economically are super intelligence, robots, solar power, and mass to space. And, of course, if you have the first two, the rest will follow. But Roadster is super cool, so we’re doing it anyway.”

Musk has said on many occasions that Optimus would be the project that would make up the vast majority of Tesla’s value in the coming years.

Robotics will be a major focus of Tesla over the coming years, especially as Musk believes Optimus will enable work to be optional for humans and will enable what he calls “High Universal Income.”

Cybercab will be a passive income opportunity for owners, Musk and Tesla have said for a very long time, as a fleet of self-driving vehicles will operate within a ride-hailing Robotaxi service that won’t require a human driver to be present.

Tesla investors are more than enthusiastic about the company’s future projects, at least from a general consensus perspective. However, it is important to note that the Roadster is a fun and cool project that pushes the boundaries of what people thought was possible for an automobile.

What we saw last week was the first true example of a flying car, and despite the backlash about how it might not contribute to Tesla’s grand ambitions, it’s okay to have fun sometimes, too.

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