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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.

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.

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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.

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.

 

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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SpaceX reportedly mulling IPO, eyeing largest of all time: report

“I do want to try to figure out some way for Tesla shareholders to participate in SpaceX. I’ve been giving a lot of thought to how to give people access to SpaceX stock,” Musk said.

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Credit: SpaceX

SpaceX is reportedly mulling an initial public offering, eyeing what would be the largest valuation at the time of availability of all time, a new report from Bloomberg said on Tuesday.

It is one of many reports involving one of Elon Musk’s companies and a massive market move, as this is not the first time we have seen reports of an IPO by SpaceX. Musk himself has also dispelled other reports in the past of a similar nature, including an xAI funding round.

SpaceX and Musk have yet to comment on the report. In the past, untrue reports were promptly replied to by the CEO; this has not yet gained any response, which is a good sign in terms of credibility.

However, he said just a few days ago that stories of this nature are inaccurate:

“There has been a lot of press claiming SpaceX is raising money at $800B, which is not accurate. SpaceX has been cash flow positive for many years and does periodic stock buybacks twice a year to provide liquidity for employees and investors. Valuation increments are a function of progress with Starship and Starlink and securing global direct-to-cell spectrum that greatly increases our addressable market. And one other thing that is arguably most significant by far.”

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Musk has discussed a potential IPO for SpaceX in recent months, as the November 6 shareholder meeting, as he commented on the “downsides” of having a public company, like litigation exposure, quarterly reporting pressures, and other inconveniences.

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Nevertheless, Musk has also said he wants there to be a way for Tesla shareholders to get in on the action. At the meeting in early November, he said:

“I do want to try to figure out some way for Tesla shareholders to participate in SpaceX. I’ve been giving a lot of thought to how to give people access to SpaceX stock.”

Additionally, he added:

“Maybe at some point., SpaceX should become a public company despite all the downsides of being public.”

Musk has been historically reluctant to take SpaceX public, at times stating it could become a barrier to colonizing Mars. That does not mean it will not happen.

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Bloomberg’s report cites multiple unidentified sources who are familiar with the matter. They indicate to the publication that SpaceX wants to go public in mid-to-late 2026, and it wants to raise $30 billion at a valuation of around $1.5 trillion.

This is not the first time SpaceX has discussed an IPO; we reported on it nine years ago. We hope it is true, as the community has spoken for a long time about having access to SpaceX stock. Legendary investor Ron Baron is one of the lucky few to be a SpaceX investor, and said it, along with Tesla, is a “lifetime investment.”

Tesla bull Ron Baron reveals $100M SpaceX investment, sees 3-5x return on TSLA

The primary driver of SpaceX’s value is Starlink, the company’s satellite internet service. Starlink contributes 60-70 percent of SpaceX’s revenue, meaning it is the primary value engine. Launch services, like Falcon 9 contracts, and the development of Starship, also play supporting roles.

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SpaceX reaches incredible milestone with Starlink program

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Credit: SpaceX

SpaceX reached an incredible milestone with its Starlink program with a launch last night, as the 3,000th satellite of the year was launched into low Earth orbit.

On Monday, SpaceX also achieved its 32nd flight with a single Falcon 9 rocket from NASA’s Kennedy Space Center.

The mission was Starlink 6-92, and it utilized the Falcon 9 B1067 for the 32nd time this year, the most-used Falcon booster. The flight delivered SpaceX’s 3000th Starlink satellite of the year, a massive achievement.

There were 29 Starlink satellites launched and deployed into LEO during this particular mission:

SpaceX has a current goal of certifying its Falcon boosters for 40 missions apiece, according to Spaceflight Now.

The flight was the 350th orbital launch from the nearby SLC-40, and the 3,000 satellites that have been successfully launched this year continue to contribute to the company’s goal of having 12,000 satellites contributing to global internet coverage.

There are over five million users of Starlink, the latest data shows.

Following the launch and stage separation, the Falcon 9 booster completed its mission with a perfect landing on the ‘Just Read the Instructions’ droneship.

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The mission was the 575th overall Falcon 9 launch, highlighting SpaceX’s operational tempo, which continues to be accelerated. The company averages two missions per week, and underscores CEO Elon Musk’s vision of a multi-planetary future, where reliable connectivity is crucial for remote work, education, and emergency response.

As Starlink expands and works toward that elusive and crucial 12,000 satellite goal, missions like 6-92 pave the way for innovations in telecommunications and enable more internet access to people across the globe.

With regulatory approvals in over 100 countries and millions of current subscribers, SpaceX continues to democratize space, proving that reusability is not just feasible, but it’s also revolutionary.

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Elon Musk

Elon Musk gives nod to SpaceX’s massive, previously impossible feat

It was the booster’s 30th flight, a scenario that seemed impossible before SpaceX became a dominant force in spaceflight. 

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Credit: SpaceX/X

Elon Musk gave a nod to one of SpaceX’s most underrated feats today. Following the successful launch of the Transporter-15 mission, SpaceX seamlessly landed another Falcon 9 booster on a droneship in the middle of the ocean. 

It was the booster’s 30th flight, a scenario that seemed impossible before SpaceX became a dominant force in spaceflight. 

Elon Musk celebrates a veteran Falcon 9 booster’s feat

SpaceX completed another major milestone for its Smallsat Rideshare program on Friday, successfully launching and deploying 140 spacecraft aboard a Falcon 9 from Vandenberg Space Force Base. The mission, known as Transporter-15, lifted off two days later than planned after a scrub attributed to a ground systems issue, according to SpaceFlight Now. SpaceX confirmed that all payloads designed to separate from the rocket were deployed as planned.

The Falcon 9 used for this flight was booster B1071, one of SpaceX’s most heavily flown rockets. With its 30th mission completed, it becomes the second booster in SpaceX’s fleet to reach that milestone. B1071’s manifest includes five National Reconnaissance Office missions, NASA’s SWOT satellite, and several previous rideshare deployments, among others. Elon Musk celebrated the milestone on X, writing “30 flights of the same rocket!” in his post. 

Skeptics once dismissed reusability as unfeasible

While rocket landings are routine for SpaceX today, that was not always the case. Industry veterans previously questioned whether reusable rockets could ever achieve meaningful cost savings or operational reliability, often citing the Space Shuttle’s partial reusability as evidence of failure. 

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In 2016, Orbital ATK’s Ben Goldberg argued during a panel that even if rockets could be reusable, they do not make a lot of sense. He took issue with Elon Musk’s claims at the time, Ars Technica reported, particularly when the SpaceX founder stated that fuel costs account for just a fraction of launch costs. 

Goldberg noted that at most, studies showed only a 30% cost reduction for low-Earth orbit missions by using a reusable rocket. “You’re not going to get 100-fold. These numbers aren’t going to change by an order of magnitude. They’re just not. That’s the state of where we are today,” he said. 

Former NASA official Dan Dumbacher, who oversaw the Space Launch System, expressed similar doubts in 2014, implying that if NASA couldn’t make full reusability viable, private firms like SpaceX faced steep odds.

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