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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)

Published

8 years ago

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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.

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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.

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).

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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!

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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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Tesla CEO Elon Musk denies ridiculous Gigafactory Shanghai rumor

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2 hours ago

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July 31, 2026

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(Credit: Tesla)

Tesla CEO Elon Musk took to his social media platform X on Thursday night to deny a ridiculous rumor regarding the sale of the company’s Chinese vehicle production plant, Gigafactory Shanghai.

On Thursday, the Wall Street Journal, citing sources familiar with the matter, claimed in a scathing new report that Tesla was exploring a potential sale of the entire China business in an effort to help bolster a potential merger between SpaceX and Tesla.

Musk immediately denied the rumor not once but twice, initially calling it “fake news,” and then calling it “absurdly fake news” in a separate post just a few moments later:

The original poster of the Wall Street Journal article that Musk saw deleted the initial post sharing the headline and the rumored sale of Tesla’s China business.

The report seemed absolutely and unequivocally false to begin with; Tesla’s business in China is among the most important pieces of the company’s business. Not only does the factory supply vehicles for the domestic market, but also for various other markets in Asia and Europe.

China is also one of the largest automotive markets in the world, and Tesla has performed well there despite the robust competition.

The speculation regarding a Tesla and SpaceX merger has started to gain steam this year as the space exploration company went public just a month ago. There has been speculation that Musk will bridge all of his companies under one “umbrella company,” and analysts believe this could happen before the end of the decade.

The Tesla and SpaceX merger everyone is talking about is quietly building

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This is the latest iteration of Musk’s very evident war on mainstream media. Reports regarding any of Musk’s companies are quick to get the dreaded “false” or “fake news” response from the CEO when they are unfounded.

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Elon Musk

Tesla AI boss reveals how big Optimus is going to get

Tesla’s Optimus chief corrected himself on X, confirming a staggering 10 million robot production target.

Published

9 hours ago

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July 31, 2026

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Tesla Optimus Gen 3 [Credit: Tesla]

Tesla’s Optimus program has a new number attached to it, after Ashok Elluswamy, the executive who has run the humanoid robot program since June 2025, posted a three word correction on X Thursday, “Correction, 10 million robots.”

The line clarifies the long term annual capacity Tesla is building toward its planned second Optimus production line at Gigafactory Texas, a figure Musk has cited repeatedly since last year’s shareholder meeting.

The scale is worth noting, because ten million robots a year would mean Tesla building more units annually than most countries sell in new cars. Tesla has framed this as a second line, not the first. The buildout is happening in two phases: a roughly one million unit per year line inside Tesla’s Fremont factory, installed on the floor space vacated when Model S and Model X production ended earlier this year, and a much larger dedicated facility under construction at Giga Texas that broke ground on its first steel structure in May. That Texas facility is the one Elluswamy’s correction refers to, and is expected to reach volume production sometime in 2027.

Tesla Optimus project fires up as Musk sees production line progress

Elluswamy took over Optimus from Milan Kovac last summer and has spent the months since talking up the program’s trajectory. Elon Musk has also floated the ten million figure at Tesla’s 2025 shareholder meeting.

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Ending Model S and Model X production to make room for the first Optimus line was one of the more consequential manufacturing decisions in the company’s recent history, retiring two flagship vehicles in favor of a robot that has yet to enter mass production. Musk has previously estimated per unit production costs at $20,000 to $25,000 once Tesla reaches a million units a year, though he hasn’t said what that cost looks like at ten times the volume.

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Autonomous vehicle red tape gets slashed by Trump Administration

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21 hours ago

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July 30, 2026

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Credit: Zoox

The Trump Administration today made several key moves to help with the deployment of autonomous vehicles by cutting overreaching red tape that has stifled growth and innovation for years.

The moves, which were put forth by the National Highway Traffic Safety Administration (NHTSA), aim to grant temporary exemptions to at least one company currently, although that could expand in the coming months. Additionally, it will work with organizations to develop standards and a sound but efficient regulatory landscape.

Zoox is the only company mentioned explicitly by the Trump Administration in its press release announcing the new terms today. They will receive a temporary two-year exemption that will allow the commercial deployment of up to 2,500 vehicles annually for two years.

There is a potential exemption for Robomart, Inc., which “requests a temporary exemption from certain FMVSS No. 500 requirements for a low-speed vehicle operated by an ADS without a human driver onboard. NHTSA will publish a separate notice seeking public comment on its merits once the initial evaluation is complete,” the agency said.

Here are the five new terms that Secretary Sean Duffy has implemented through the NHTSA today:

  1. Allow Zoox to commercially deploy its robotaxis through a temporary exemption.
    This temporary exemption will allow the commercial deployment of up to 2,500 vehicles annually for two years, subject to an enhanced, adaptable oversight structure that can evolve as Zoox’s technology advances.
  2. Accelerate development of first-ever AV performance standards through a partnership with SAE Industry Technologies Consortia (ITC).
    This partnership will fund a three-year, $5 million “A2SCEND” consortium, bringing together experts to gather data and accelerate creation of the first-ever AV performance standards. This project will inform a single national standard for AV safety to eliminate the patchwork regulatory landscape that has stifled innovation for years.
  3. Publish an interim final rule that allows vehicles manufactured prior to an exemption to be eligible for a commercial deployment exemption.
    This rule will modernize the application process and improve access to exemptions for innovators, including AV developers, by granting the NHTSA Administrator the discretion to apply temporary exemptions to vehicles manufactured prior to the effective date of an exemption grant.
  4. Streamline the application process for Part 555 exemptions by updating guidance and soliciting feedback from the public.
    By updating the Part 555 exemption process—which allows automakers to temporarily sell a limited number of non-compliant vehicles, primarily to test new technologies—NHTSA is aiming to create a more flexible oversight structure for exemptions and summarize recent AV framework activities, including expanded exemption pathways, streamlined crash reporting, and ongoing efforts to modernize Federal Motor Vehicle Safety Standards (FMVSS).
  5. Establish a new Federal Docket for public feedback on NHTSA’s updated safe AV development and deployment guidance.
    NHTSA is updating its technical guidance for AVs for the first time since 2017—focusing on key safety areas like emergency responder interactions, safety management systems, remote assistance, and post-crash behavior to help the industry scale up driverless deployments safely.

Additionally, the NHTSA said it has modernized some safety standards by proposing updates to:

  • FMVSS 102 – Transmission shifting
  • FMVSS 103/104 – Windshield defrosting and wiping
  • FMVSS 110 – Tire placards
  • FMVSS 135 – Braking systems
  • FMVSS 101 – Controls and displays
  • FMVSS 108 – Vehicle lighting
  • FMVSS 111 – Mirrors and rearview display
  • FMVSS 126 – Electronic stability control systems
  • FMVSS 201/208 – Sun visors and warning labels

These changes aim to make the regulatory process for autonomous vehicles more streamlined and efficient, which could help the U.S. gain dominance over autonomous vehicle systems moving forward.

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