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SpaceX sends “radically redesigned” Starship engine to Texas for hot-fire tests
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.
Engines currently on Starship hopper are a blend of Raptor development & operational parts. First hopper engine to be fired is almost finished assembly in California. Probably fires next month.
— Elon Musk (@elonmusk) January 5, 2019
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.
Mach diamonds pic.twitter.com/TCX7ZGFnN0
— Elon Musk (@elonmusk) September 26, 2016
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.
SpaceX has completed over 1,200 seconds of firing across 42 main Raptor engine tests. pic.twitter.com/EhxbPjd8Cj
— SpaceX (@SpaceX) September 29, 2017
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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- The only official render of Raptor, published by SpaceX in September 2016. The Raptor departing Hawthorne in Jan ’19 looked reasonably similar. (SpaceX)
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- SpaceX technicians wrench on Merlin 1D and Merlin Vacuum engines. Raptor was apparently dramatically larger in person. (SpaceX)
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- Starhopper’s Raptors feature a very distinct seam and second curve, indicative of a dual-bell nozzle. (NASASpaceflight /u/bocachicagal)
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.
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- SpaceX’s current Texas facilities feature a test stand for Raptor, the engine intended to power BFR and BFS to Mars. (SpaceX)
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- SpaceX’s subscale Raptor engine has completed more than 1200 seconds of testing in less than two years. (SpaceX)
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- A gif of Raptor throttling over the course of a 90+ second static-fire test in McGregor, Texas. (SpaceX)
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- A September 2018 render of Starship (then BFS) shows one of the vehicle’s two hinged wings/fins/legs. (SpaceX)
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.
Yes. Radically redesigned Raptor ready to fire next month.
— Elon Musk (@elonmusk) December 22, 2018
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.
The Tesla Semi is entering a new Pilot Program with Paper Transport, LLC (PTI), a Wisconsin-based transportation provider. The company will test the Semi’s Long Range configuration through “dedicated operations within the Chicago market.”
Chicago presents an interesting challenge for the Semi, as it will be a colder-weather climate that will test the Semi’s ability to operate in lower temperatures and in potentially large accumulations of snow. This is something Tesla has been testing with the Semi in Alaska and even in Northern California during the colder months, but Chicago will present a truly tough midwestern winter.
Tesla Semi spotted on journey home after winter performance testing
PTI says it is using the Semi to evaluate its strategy of reducing transportation emissions while maintaining performance, reliability, and cost efficiency. These are major arguments for the Semi being introduced into new fleets.
CEO of PTI Tyler Ellison said:
“PTI has been a leader in sustainable transportation solutions for over 15 years. We take a consultative approach to helping customers identify and implement the right transportation solution for their network. Our partnership with Tesla expands our portfolio alongside renewable natural gas and intermodal, giving customers more ways to reduce Scope 3 emissions without compromising service or economics.”
PTI is far from the first company to adopt the Semi within a fleet, as Tesla entered strategic agreements with PepsiCo. and its subsidiary Frito-Lay for a Pilot Program that extended throughout the California region.
Tesla has let companies like those utilize the Semi to determine whether it would be suitable for their operations. Additionally, Tesla gets valuable information regarding the Semi’s performance, knowing what to improve and what is ideal for companies that will utilize the all-electric truck for regional and nationwide logistics.
PTI plans to utilize the Long Range configuration, which is priced at $290,000 and features a range of approximately 500 miles, a three-motor powertrain, up to 800 kW of drive power, and consumption of just 1.7 kWh per mile.
Tesla Semi pricing revealed after company uncovers trim levels
VP of Maintenance at PTI, Bryan Ellen, added:
“We are excited to partner with Tesla, leveraging their ever-evolving technology. We are bullish in our estimation of the parallels available between our dedicated model and the efficiency of their fully electric Class 8 tractor. We anticipate a growing synergy between our businesses as we work to facilitate this sustainable solution for our customers.”
PTI has logged more than 87 million miles using sources like compressed and renewable gas, but now is looking to take it a step further with fully electric operations.
Tesla revealed on Monday that it is building a new autonomous vehicle at Gigafactory Texas, its plant just outside of the City of Austin. This particular vehicle will be geared toward those who are in need of a wheelchair-accessible car that would require no human driver for operation.
According to a new report from Wired, Tesla’s Senior Policy Advisor, India Herdman, told members of the Washington D.C. City Council on Monday:
“We are in development for a purpose-built, wheelchair-accessible autonomous vehicle. We know that paratransit can be very difficult, and people who are confined to wheelchairs permanently should still be able to move around freely, so that is an active product being built by Tesla in Texas.”
This builds upon what CEO Elon Musk said last year on X, which confirmed the company was working on accessible rides within its Robotaxi platform, which currently is confined to the Model Y.
Absolutely
— Elon Musk (@elonmusk) September 19, 2025
Tesla is also developing the Cybercab, which started employee rides last week. However, this vehicle is not necessarily geared toward wheelchair accessibility.
That leaves a major gap in the autonomous ride-sharing program that Tesla is attempting to build; the company has been pretty clear that it does not want to complicate its manufacturing lines by bringing in a wide array of body styles.
However, it seems necessary to have something larger that could help transport people to appointments when they cannot drive. For wheelchair accessibility, the Robovan, which was unveiled at the “We, Robot” event in October 2024, seems to be the most ideal solution:
Herdman did not indicate whether she was referring to the Robovan or if Tesla is building yet another body style that is geared toward full autonomy but also caters to the handicapped.
Tesla might need to develop something specifically for the handicapped in order to align with the Americans with Disabilities Act, which prevents discrimination against people with disabilities in transportation services. Uber was hit with a lawsuit late last year for “refusing to reasonably modify its policies, practices, or procedures where necessary to avoid discriminating against riders with disabilities.”
Tesla would obviously like to avoid this.
It will be interesting to see what Tesla will do with this project, and whether it will introduce something new to the market or just continue with the Robovan.
Tesla weirdly confirmed that its steering wheel-less and pedal-less Cybercab vehicle is now in the process of giving employees rides, a huge milestone for the vehicle program.
But the entire thing was super strange. On Friday, Tesla released a video stating that there was “Cool news from Giga Texas” and that employees were now taking rides in Cybercabs that have no manual controls. The units seen on public roads are engineering vehicles that have manual controls inside, a necessity as Tesla moved through the testing phase.
However, Tesla removed the video and reposted it shortly after with a more vague title. It seems like the employee rides are still going, but the video was adjusted slightly. The initial upload showed employees doing things like watching movies and adjusting the climate, but these snippets were removed in the second upload.
Cool news from Giga Texas pic.twitter.com/gvbG456Tzw
— Tesla Robotaxi (@robotaxi) July 11, 2026
Both images below were uploaded with the first video, but were removed after Tesla re-uploaded the announcement. These are not available in the second upload
Credit: Tesla
Credit: Tesla
Nevertheless, the announcement from Tesla is that the Cybercab is operating with employees inside who can control the vehicle’s audio, video, climate, and destination settings through their smartphone app.
Tesla has already been testing Cybercab engineering units, but last month, it was able to self-certify for SAE Level 4, which would enable unsupervised self-driving in Texas. The company is moving toward that, and the plans have always been to launch Cybercab rides this year.
The Cybercab is potentially looked at as the next generation of Tesla’s mobility leg. For the past 15 years, the company has been known as somewhat of an automaker, among many other things. However, these passenger vehicles that Tesla has manufactured are now moving into a new realm, as they will eventually drive themselves with no supervision thanks to the Full Self-Driving suite.
The Cybercab is just the next step of that: a true vehicle developed for the sole purpose of ride-hailing. It has no human controls, it has only two seats, and it will get passengers from Point A to Point B with no awkward driver, no need for manual inputs, and with no stress.
Tesla is moving forward with other developments related to the Cybercab project as well. However, the big announcement will come when Tesla finally announces that it is launching Cybercab rides to the general public, something that it plans to launch either late this year or early 2027.
Tesla Semi enters new Pilot Program with interesting challenge
Tesla is building a wheelchair-accessible Robotaxi
