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SpaceX sends “radically redesigned” Starship engine to Texas for hot-fire tests

As of September 2017, subscale Raptor engines had been cumulatively fired for more than 1200 seconds in just 12 months of testing. (SpaceX)

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SpaceX has shipped one of the first of a group of Starship engines known as Raptor, described last month by CEO Elon Musk as “radically redesigned”. A culmination of more than 24 months of prototype testing, the first flight-worthy Raptor could be ignited for the first time as early as February.

According to Musk, three of these redesigned Raptors will power the first full-scale BFR prototype, a Starship (upper stage) test article meant to conduct relatively low-altitude, low-velocity hop tests over the southern tip of Texas. Those tests could also begin next month, although a debut sometime in March or April is increasingly likely.

Effectively designed on a blank slate, Raptor began full-scale component-level tests in 2014 at NASA’s Mississippi-based Stennis Space Center, evolving from main injector development to oxygen preburner hot-fires in 2015. Soon after Raptor’s prototype preburner design was validated at Stennis, SpaceX moved testing to its privately-owned and operated facilities in McGregor, Texas, where Raptor static fire testing has remained since.

Just days before CEO Elon Musk was scheduled to reveal SpaceX’s next-generation rocket (BFR, formerly known as the Interplanetary Transport System or ITS) in September 2016, he announced in a tweet that propulsion engineers and technicians had successful hot-fired an integrated Raptor prototype – albeit subscale – for the first time ever. Just 12 months later, Musk once again took to the stage to announce an update to BFR’s design, while also revealing that prototype Raptor engines had already completed more than 1200 seconds (20 minutes) of cumulative hot-fire tests, an extremely aggressive and encouraging rate of progress for such a new engine.

Although Raptor undoubtedly borrows heavily from much of the same expertise that designed Merlin 1 and operated and improved it for years, that is roughly where the similarities between Raptor and M1D end. M1D, powered by refined kerosene (RP-1) and liquid oxygen, uses a combustion cycle (gas-generator) that is relatively simple and reliable at the cost of engine efficiency, although SpaceX propulsion expertise still managed to give M1D the highest thrust-to-weight ratio of any liquid rocket engine ever flown. Still, measured by ISP (instantaneous specific impulse), M1D’s inefficient kerolox gas-generator cycle ultimately means that the engine simply can’t compete with the performance of engines with more efficient propellants and combustion cycles.

While SpaceX’s Falcon 9 and Heavy rockets – powered by Merlin 1D and Merlin Vacuum – are more than adequate in and around Earth orbit, a far more efficient engine was needed for the company to enable the sort of interplanetary colonization Musk had in mind when he created SpaceX. Raptor was the answer. Ultimately settling on liquid methane and oxygen (methalox) as the propellant and a full-flow staged-combustion (FFSC) cycle, Raptor was designed to be extraordinarily reliable and efficient in order to safely power a spacecraft (BFS/Starship) meant to ferry dozens or hundreds of people to and from Mars.

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An excellent NASASpaceflight article explores the engine’s journey from a blank sheet to integrated static-fire tests and offers a deeper explanation of the technical details.

Raptor enters a new era

For all the extensive and invaluable testing SpaceX has done with a series of prototype Raptor engines, the engines tested were subscale versions with around 30% the thrust of the c. 2016 Raptor and around 40-50% of the updated c. 2017 iteration, producing almost the same amount of thrust as Merlin 1D (914 kN to Raptor’s ~1000 kN). In September 2018, Musk described Raptor as an “approximately…200-ton (~2000 kN) thrust engine” that would eventually operate with a chamber pressure as high as 300 bar (an extraordinary ~4400 psi), requiring at least one of the FFSC engine’s two preburners (used to power separate turbopumps) to operate at a truly terrifying ~810 bar (nearly 12,000 psi).

Conveniently stood beside a Merlin 1D engine also ready for hot-fire acceptance testing, the Raptor engine spotted departing SpaceX’s Hawthorne, CA factory last week was reportedly immense in person, towering over an M1D engine. Raptor also featured a mass of spaghetti-like plumbing (complexity necessary for its advanced combustion cycle), with a significant fraction of the metallic pipes and tubes displaying mirror-like finishes. Most notable was an obvious secondary preburner/turbopump stack and the lack of any exhaust port, whereas M1D relies on a single turbopump and exhausts the gases used to power it. Raptor’s full-flow staged-combustion cycle uses separate oxygen and methane preburners to power separate turbopumps, significantly improving mass flow rate and smoothing out combustion mixing.

 

Unlike all previous hot-fired Raptors, those shipping now to McGregor, Texas are expected to be the first completed engines with a finalized design, arrived at only after a period of extensive testing and iterative improvement. They also appear to be full-scale, meaning that the test bays dedicated to Raptor will likely need to be upgraded (if they haven’t been already) to support a two- or threefold increase in maximum thrust.

SpaceX’s Starship hopper will need three finalized engines, meaning that the Raptor now in McGregor, Texas may not have been the first to arrive. Nevertheless, the shipment of full-scale hardware is always an extremely encouraging milestone for any advanced technology development program, while also foreshadowing the first imminent static-fires of the “radcally redesigned” rocket engine. With hardware now at the test site before January is out, a February test debut – one month behind a January debut teased by Elon Musk last December – is not out of the question.


Check out Teslarati’s newsletters for prompt updates, on-the-ground perspectives, and unique glimpses of SpaceX’s rocket launch and recovery processes!

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 Roadster owners to get “Flying Stunt Mode” and looping track access

Musk says Roadster owners can command the unveiling stunts autonomously, with a Texas looping track.

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Elon Musk says owners of the new Tesla Roadster will be able to ask the car to perform the stunts Tesla showed at its unveiling, with the car doing the driving itself. Musk made the comment Saturday in a reply on X to tech blogger Robert Scoble, and he added a promise of a looping track at Tesla’s Texas headquarters.

Scoble had argued that the person in the Roadster is not really driving it. In his description, the driver operates a computer that tells another computer what to do, with steering, braking and acceleration all handled by wire. Musk answered, “True. You will be able to ask the Roadster to perform any of the tricks shown autonomously, as it will be sentient. Also, we will have a wild looping track (crazier even than Hot Wheels) at our Texas HQ where you can test out your Roadster.”

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At the October 15 event outside Waco, the car drove up a curved ramp until it was upside down, flew off on cold gas thrusters, flipped and landed. It also hovered over a Cybercab, Cybertruck, Semi, Model Y and Model 3 while moving. As we noted in our breakdown of the three Roadster configurations, Musk said at the event that the car “literally is just going to puff itself up” to perform the maneuvers whenever an owner wants. Saturday’s reply adds that the car would run them on its own.

Tesla has described some of the hardware that would make that possible. The Roadster uses steer by wire with a yoke, and its cold gas thrusters rely on electric actuators for small adjustments in flight. A fan system under the car creates suction, which Tesla says is strong enough to hold it upside down, a setup we covered in our look at the Roadster’s fan system and thrusters.

Musk did not say when an autonomous stunt feature might arrive, how it would work, or what he means by sentient. He also gave no size, location or opening date for the Texas track. Production is planned for Giga Texas in 2027 or 2028, and Tesla says the car is not approved for public road use. The Rocket version, the one built to fly, is invite only.

The comment follows a week of Musk teasing the event, including his claim that the demo would be a banger, which we covered before the stream. Tesla reports third quarter earnings on October 21, and shareholders can submit and vote on questions through the Say portal until 4 p.m. EDT on October 20, according to our earnings Q&A preview. A question about autonomous Roadster stunts and the Texas track would be a quick way to get specifics from management.

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Elon Musk

How to use Grok Bot to block spam calls and texts

Musk told users to ask Grok Bot to scrub their phone numbers from spam lists.

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Elon Musk has a new use case for Grok Bot, and it is the spam call. On Thursday he replied to an X user named Arash with a short instruction: “Ask your @Grok @Bot to remove your phone number from spam call & text lists!” Arash had said he got tired of the calls, had an AI bot find his number on listing sites and file removal requests, and packaged the process as a free skill for others.

The skill is called Spam-Call Scrubber, which is described to find a phone number on people search sites and data brokers, submits the opt outs, completes the confirmation emails those sites send back, and rechecks on a schedule the user picks. Using it requires the Grok Bot app. The pitch is time saved, since most broker opt outs sit behind separate forms on separate sites.



Musk said Grok Bot now gives each bot its own email address, and that it can detect scam emails. On Thursday he also said SpaceX would make users whole if the bot botches a purchase or leaks a card, then told users to shop away from Amazon after the retailer blocked the agent, as Teslarati reported. The terms of service we reviewed at the time put responsibility for what an agent does on the user.

For Tesla owners, Grok Bot is not just a phone app. Tesla brought Grok Bot into its vehicles on September 22, and we argued earlier this week that the Cybercab’s real advantage may be the errands it runs during a ride. Every Cybercab and the rest of the Model Y Robotaxi fleet has it enabled. The more routine tasks like this one become, the more a rider has reason to hand over something personal in the back seat.

The new Spam-Call Scrubber skill can be downloaded for free and works on sites that honor removal requests, while noting that listings can reappear, and illegal robocallers do not check any registry. Whether Spam-Call Scrubber cuts anyone’s call volume is something the first wave of users will find out, and Musk’s endorsement guarantees that wave is coming.

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Investor's Corner

Tesla’s flying Roadster just revealed something bigger than the car

Analysts say the Roadster demo puts a Tesla and SpaceX merger back on the table.

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Tesla’s new Roadster, upside down and trailing cold gas thruster smoke, flips over a lineup of Tesla vehicles at the Roadster unveiling near Waco, Texas on October 15, 2026. (Image: Tesla)
Tesla’s new Roadster, upside down and trailing cold gas thruster smoke, flips over a lineup of Tesla vehicles at the Roadster unveiling near Waco, Texas on October 15, 2026. (Image: Tesla)

The Roadster unveiling near Waco ended Thursday night, and by Friday morning much of the investor reaction had less to do with the car than with who owns the rocket technology inside it.

Wedbush analyst Dan Ives said the event “puts the Tesla/SpaceX relationship on the table in a tangible way,” pointing to the propulsion, pressure vessel and control hardware sitting on a Tesla product. Gene Munster of Deepwater Asset Management called the demo “a ridiculous display of engineering” with “no commercial value” beyond embarrassing traditional automakers, though he said it showed Musk wants the two companies together.

The more specific forecast came a day earlier from Barclays. Analyst Dan Levy told clients a deal could be announced before Tesla’s annual meeting, which must happen by December 6, and that an announcement in late October or early November could make shareholder approval harder. Barclays expects SpaceX to be the buyer in an all stock deal, with Tesla holders receiving SpaceX shares at a premium, based on market values of roughly $2.1 trillion for SpaceX and $1.5 trillion for Tesla. If nothing lands around the meeting, the bank still sees an announcement within 6 to 12 months.

The Roadster demo just added more weight to merger speculations. Tesla’s demo used cold gas thrusters and pressure tanks of the kind SpaceX uses on Falcon 9, and Musk described the car as a collaboration between Tesla and SpaceX engineers, as we mentioned in our breakdown of the three Roadster configurations.


Musk has not publicly addressed a deal since the event, as far as we have seen. His most direct answer remains the one he gave at the All In Summit, when he said that with so much collaboration, “who can imagine what action one might take” without ruling anything out. Ives has held to a 2027 timeline since his March note, and Musk pushed back on the China piece of the speculation when ARK floated a year end announcement in August.

The next test is Tesla’s third quarter earnings call on October 21. However, we recall in July that Musk told analysts, “we can’t talk about combining companies and that kind of thing on an earnings call,” so a clear answer wouldn’t be expected.

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