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SpaceX’s Starship hopper spotted with trio of dual-bell Raptor engines

Starship revealed a trio of what appear to be new Raptor engines when SpaceX technicians moved the assembly from stand to ground. (NSF - bocachicagal)

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Following a brief ‘hop’ (via crane) off of a concrete build stand, the aft section of SpaceX’s first full-scale Starship hopper (Starhopper?) revealed that SpaceX technicians have already installed what appear to be three real Raptor engines, presumably the first time the propulsion system has ever been mounted to something that might eventually fly.

For a number of reasons, there is a strong chance that these Raptors are actually just boilerplate placeholders standing in as structural guides for the real deal some months down the line. On the other hand, there are also a number of reasons to assume that these apparent engines are indeed real Raptors.

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Despite an already shocking series of rapid-fire developments in the South Texas Starhopper saga, the abrupt appearance of what appears to be three Raptor engines – mirroring CEO Elon Musk’s recent statement that the test vehicle would sport three Raptors – is by far the most unexpected moment yet for the prototype Starship. Purportedly a full-scale prototype of BFR’s upper stage/spaceship (now known as Starship), Musk indicated over the last two weeks that the hopper has been designed to perform a number of hop tests in which the craft’s three Raptors would power it to a range of (relatively low) altitudes above Boca Chica, Texas.

According to a recent FCC filing related to this test program, SpaceX is currently seeking a license for Starship hop tests that will not exceed 5 km (3.1 mi) in altitude and/or 6 minutes in duration. There is admittedly nothing mentioned about the maximum allowed velocity during those tests, but – much like Blue Origin performs supersonic tests of New Shepard in Cape Horn, Texas – SpaceX will likely seek and be granted permission to break the sound barrier during those hypothetical tests. Nevertheless, a 5km ceiling is a fairly significant cap on the range of performance Starhopper will be able to test – accelerating vertically at 2Gs, Starhopper could travel from sea level to 5km in less than 30 seconds while reaching speeds no higher than Mach 1-1.5.

 

Combined with the apparent fact that this Starhopper’s fins seem unlikely to ever actuate (i.e. no aerodynamic control surfaces), it’s probable that this ad hoc prototype is only meant to perform a very limited range of hop tests, perhaps as basic as ironing out the kinks of operating a trio of gimballed Raptors and ensuring that they can safely and reliably launch, hover, and land a very large Starship-shaped mass simulator. Falcon 9’s Grasshopper and F9R reusability testbeds performed a very similar task some five years ago, offering SpaceX engineers the opportunity to optimize software and hardware needed to reliably recover real orbital-class rockets after launch. Although Falcon 9 has nine gimballed Merlin 1D engines, SpaceX has long sided with the sole center Merlin as the dedicated landing engine and has only briefly experimented with triple-Merlin landing burns.

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Dual-expansion whaaaaat?

According to Musk, Raptor –  an advanced liquid methane and oxygen engine with a uniquely efficient propulsion cycle – was expected to produce an impressive ~2000 kN (200 ton, 450K lbf) of thrust in its finished form as of September 2018. However, Musk also mentioned in a late-2017 Reddit AMA that SpaceX engineers were modifying the ship’s design to ensure engine-out reliability during all regimes of flight, landing in particular. To accomplish this feat with an engine as powerful as Raptor, two or three Raptors – capable of producing as much as 600 tons of thrust total – would need to reliably throttle as low as 25%, assuming a landing mass of around 150t. To allow a nearly empty ship (~100t) to still reliably land with three Raptors ignited, the engines would need to be able to throttle to 20% or less.

A trio of Raptors (or Raptor stand-ins) were spotted on Starhopper on Dec 31 by NASASpaceflight user bocachicagal.

Known as deep throttling in rocketry, ensuring stable combustion and thrust at 20% (let alone 40%) throttle is an extraordinarily challenging feat, often subjecting engines to forces that can literally tear non-optimized hardware apart. To achieve such a deep throttle capability without excessively disrupting the engine’s design, SpaceX appears to have potentially sided with less efficient but extremely simple alternative, known as a dual-bell (or dual-expansion) rocket nozzle. A 1999 Rocketdyne paper concisely explained the primary draws of such a nozzle:

“The [altitude-compensating] dual-bell nozzle offers a unique combination of performance, simplicity, low weight, and ease of cooling” – Horn & Fisher, 1999

Given that SpaceX has decided to delay the introduction and certification of a vacuum-optimized Raptor engine, choosing to instead use the same Raptor on both BFR stages, something like a dual-bell nozzle would be one of the best possible ways for the company to retain some of the efficiency benefits of a vacuum engine while also drastically improving design simplicity, ease of manufacturing, and cutting development time. Aside from offering efficiency gains by way of altitude compensation, a dual-bell nozzle also happens to enable a given engine to operate a much wider throttle range by mitigating problems with flow separation and instability.

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For Starhopper and Starship, both aspects are an undeniable net-gain and it’s entirely possible that these dual-bell nozzles – if successfully demonstrated – could find their way onto Falcon 9 and Falcon Heavy to further boost their booster performance and efficiency.


For prompt updates, on-the-ground perspectives, and unique glimpses of SpaceX’s rocket recovery fleet check out our brand new LaunchPad and LandingZone newsletters!

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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

TIME honors SpaceX’s Gwynne Shotwell: From employee No. 7 to world’s most valuable company

Time Magazine honors Gwynne Shotwell as SpaceX reaches a $1.25 trillion valuation and eyes its IPO.

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TIME Magazine has put SpaceX President and COO Gwynne Shotwell on its cover, and the timing could not be more fitting. Published today, the profile of Shotwell arrives at a moment when the company she has quietly run for more than two decades stands at the center of the most consequential developments in aerospace, artificial intelligence, and the future of human civilization.

Shotwell joined SpaceX in 2002 as its seventh employee and has never stopped expanding her role. She oversees day-to-day operations across multiple executive teams spanning Falcon, Starlink, Starship, and now xAI following SpaceX’s February 2026 merger with Elon Musk’s artificial intelligence company, a deal that made SpaceX the world’s most valuable private company at a reported valuation of $1.25 trillion. A highly anticipated IPO is expected in the second quarter of 2026.

Will Tesla join the fold? Predicting a triple merger with SpaceX and xAI

Her track record is historic. She oversaw the first landing of an orbital rocket’s first stage, the first reuse and re-landing of an orbital booster, and the first private crewed launch to Earth orbit in May 2020. She built the Falcon launch manifest from nothing to more than 170 contracted missions representing over $20 billion in business. Under her operational leadership, SpaceX completed 96 successful missions in 2023 alone and has now flown more than 20 crewed Falcon 9 missions. Starlink, which she championed as a financial pillar of the company long before it was a mainstream topic, now connects tens of millions of users worldwide and provided a critical communications lifeline to Ukraine following the 2022 invasion.

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Elon Musk has never been shy about what Shotwell means to him and to SpaceX. When she shared her vision for worldwide internet connectivity through Starlink, Musk responded on X with a simple statement, “Gwynne is awesome.” It is a sentiment that has been echoed across the industry. NASA Administrator Bill Nelson once said of Musk: “One of the most important decisions he made, as a matter of fact, is he picked a president named Gwynne Shotwell. She runs SpaceX. She is excellent.”


Now, with Starship targeting its first crewed lunar landing under the Artemis program by 2028, an xAI integration underway, and a pending IPO that could reshape capital markets, Shotwell’s mandate has never been larger. She told Time that 18 Starships are already in various stages of construction at Starbase. “By 2028,” she said, gesturing across the factory floor, “these should be long gone. They better have flown by then.” If Shotwell’s history at SpaceX is any guide, they will.

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SpaceX’s IPO might arrive sooner than you think

Musk has hinted for years that an eventual public offering was inevitable, though he has stressed the need to maintain operational focus. Insiders have told outlets that the CEO is pushing for a significant retail investor allocation, reportedly more than 20 percent of shares, and tighter lock-up periods to limit early selling pressure.

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Credit: SpaceX | X

Elon Musk’s SpaceX is on the verge of one of the most anticipated Initial Public Offerings (IPO) in history.

However, a new report from The Information indicates the rocket and satellite giant is aiming to file its IPO prospectus with U.S. regulators as soon as this week, or early next week at the latest.

People familiar with the plans told The Information that advisers involved in the process expect the IPO could raise more than 75 billion dollars, potentially making it the largest stock market debut ever and eclipsing Saudi Aramco’s 29.4 billion dollar offering in 2019.

The filing would mark the formal start of what has long been rumored: SpaceX’s transition from a closely held private powerhouse to a publicly traded company.

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The timing aligns with earlier signals.

In late February, Bloomberg reported that SpaceX was targeting a confidential IPO filing in March and a possible public listing in June, with a valuation north of 1.75 trillion dollars. At the time, the company’s private valuation hovered around 1.25 trillion dollars.

SpaceX considering confidential IPO filing this March: report

Starlink, SpaceX’s satellite internet constellation, has been the primary driver of that surge, now serving millions of customers worldwide and generating steady revenue. Recent Starship test flights and a record pace of Falcon launches have further bolstered investor confidence.

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Musk has hinted for years that an eventual public offering was inevitable, though he has stressed the need to maintain operational focus. Insiders have told outlets that the CEO is pushing for a significant retail investor allocation, reportedly more than 20 percent of shares, and tighter lock-up periods to limit early selling pressure.

A June listing would give SpaceX immediate access to public capital markets at a moment when demand for space-related stocks remains high. It would also allow early employees and long-time investors to cash out portions of their stakes while giving everyday shareholders a chance to own a piece of the company behind reusable rockets, global broadband, and NASA contracts.

Of course, nothing is certain until the SEC filing appears. Market conditions, regulatory reviews, and Musk’s own schedule could still shift timelines.

Yet the latest word from The Information suggests the window has opened. If the filing lands this week, SpaceX’s roadshow could begin in earnest within weeks, setting the stage for what many analysts already call the IPO of the decade.

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Elon Musk

Elon Musk’s TERAFAB project: Everything you need to know

The CEO has hinted heavily for several quarters that it would probably need to produce its own computing power to stay up to speed on the demand it is facing for its projects. It is now taking matters into its own hands.

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Credit: SpaceX

On Sunday, Elon Musk formally made TERAFAB official—a groundbreaking $20-25 billion joint venture uniting Tesla, SpaceX, and xAI, three of the world’s richest man’s most significant and powerful ventures.

Musk described the project as “the most epic chip building exercise in history by far.”

Elon Musk launches TERAFAB: The $25B Tesla-SpaceXAI chip factory that will rewire the AI industry

The initiative aims to produce over one terawatt of AI compute annually, dwarfing the global industry’s current output of roughly 20 gigawatts per year. Musk framed the effort as “the next step towards becoming a galactic civilization,” positioning it as essential for scaling humanity into a multi-planetary species.

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The Need for TERAFAB

Existing chip suppliers such as TSMC, Samsung, and Micron cannot expand quickly enough to meet the explosive demand for AI hardware.

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Musk explained the situation clearly:

“We’re very grateful to our existing supply chain… but there’s a maximum rate at which they’re comfortable expanding. We either build the Terafab or we don’t have the chips, and we need the chips, so we build the Terafab.”

The CEO has hinted heavily for several quarters that it would probably need to produce its own computing power to stay up to speed on the demand it is facing for its projects. It is now taking matters into its own hands.

Chip Types and Production Goals

The facility will manufacture two specialized chip families, according to the presentation:

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  • Edge-inference AI5 and AI6 processors optimized for Tesla’s Optimus humanoid robots and Full Self-Driving systems in vehicles and Robotaxis
  • High-power D3 chips hardened for space environments

Musk outlined annual output targets, which are between 100 and 200 gigawatts of terrestrial compute for robotics, supporting Musk’s vision of producing 1-10 billion Optimus units per year, and the majority (80%) of chips dedicated to orbital AI data centers. Overall, TERAFAB aims to produce 100-200 billion custom AI and memory chips each year.

Scale and Strategy

The size of the TERAFAB project will be remarkable, as Musk indicated after the presentation that the entire Gigafactory Texas campus would not be large enough to fit the needs of the project. In fact, Musk said it would be around 100 million square feet in size, the equivalent of 15 Pentagons or three Central Parks.

Yes, the one in New York City.

Construction will begin with an “advanced technology fab” on the Giga Texas campus in Austin, enabling rapid iteration: design a chip, fabricate lithography masks, produce and test wafers, all within days.

However, the full-scale TERAFAB requires thousands of acres and over 10 gigawatts of power, far exceeding what Giga Texas can accommodate. Musk stated:

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“We couldn’t possibly fit the Terafab on the GigaTexas campus. It will be far bigger than everything else combined there.”

Multiple large sites are currently under consideration, but this will need a sprawling land mass to get started.

Key Applications

TERAFAB will be a crucial part of the development of some of Tesla’s most valuable projects, including Optimus and data center development, especially from an orbital standpoint. For that reason, we will break this down into Terrestrial and Orbital applications:

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  • Terrestrial: Powers autonomous vehicle fleets and billions of Optimus robots performing physical labor
  • Orbital: Starship will launch massive AI satellite constellations, starting with 100-kilowatt “Mini” units, and scaling to larger Megawatt models, creating the world’s largest data center in low-Earth orbit.

Space-based advantages include five times greater solar irradiance, efficient vacuum heat rejection, and freedom from terrestrial grid constraints (U.S. electricity generation totals just 0.5 terawatts). Musk emphasized the principle:

“Quantity has a quality all its own.”

We wrote about SpaceX’s recent filing with the FCC for 1 million orbital data center plans.

Strategic Vision

TERAFAB represents vertical integration at an unprecedented scale, combining AI hardware, robotics, and orbital infrastructure.

Musk described the project as “the final missing piece of the puzzle.” With production ramping toward 2027, TERAFAB is set to accelerate an era of abundance, transforming science fiction into reality and positioning Musk’s companies at the forefront of galactic-scale innovation.

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