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SpaceX’s path to refueling Starships in space is clearer than it seems

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4 years ago

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Perhaps the single biggest mystery of SpaceX’s Starship program is how exactly the company plans to refuel the largest spacecraft ever built after they reach orbit.

First revealed in September 2016 as the Interplanetary Transport System (ITS), SpaceX has radically redesigned its next-generation rocket several times over the last half-decade. Several crucial aspects have nevertheless persisted. Five years later, Starship (formerly ITS and BFR) is still a two-stage rocket powered by Raptor engines that burn a fuel-rich mixture of liquid methane (LCH4) and liquid oxygen (LOx). Despite being significantly scaled back from ITS, Starship will be about the same height (120 m or 390 ft) and is still on track to be the tallest, heaviest, and most powerful rocket ever launched by a large margin.

Building off of years of growing expertise from dozens of Falcon 9 and Falcon Heavy launches, the most important fundamental design goal of Starship is full and rapid reusability – propellant being the only thing intentionally ‘expended’ during launches. However, like BFR and ITS before it, the overarching purpose of Starship is to support SpaceX’s founding goal of making humanity multiplanetary and building a self-sustaining city on Mars. For Starship to have even a chance of accomplishing that monumental feat, SpaceX will not only have to build the most easily and rapidly reusable rocket and spacecraft in history, but it will also have to master orbital refueling.

The reuse/refuel equation

In the context of SpaceX’s goals of expanding humanity to Mars, a mastery of reusability and orbital refueling are mutually inclusive. Without both, neither alone will enable the creation of a sustainable city on Mars. A Starship launch system that can be fully reused on a weekly or even daily basis but can’t be rapidly and easily refueled in space simply doesn’t have the performance needed to affordably build, supply, and populate a city on another planet (or Moon). A Starship launch system that can be easily refueled but is not rapidly and fully reusable could allow for some degree of interplanetary transport and the creation of a minimal human outpost on Mars, but it would probably be one or two magnitudes more difficult, risky, and expensive to operate and would require a huge fleet of ships and boosters from the start.

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The question of how SpaceX will make Starship the world’s most rapidly, fully, and cheaply reusable rocket is a hard one, but it’s not all that difficult to extrapolate from where the company is today. Currently, the turnaround record (time between two flights) for Falcon boosters is two launches in less than four weeks (27 days). SpaceX’s orbital-class reuse is also making strides and the company recently flew the same orbital Crew Dragon capsule twice in just 137 days (less than five months) – fast approaching turnarounds similar to NASA’s Space Shuttle average, the only other reusable orbital spacecraft in history.

SpaceX’s current fleet of four reusable Dragon spacecraft. (NASA/Mike Hopkins/ESA/Thomas Pesquet)
Pictured here during its last launch, Falcon 9 B1060 owns SpaceX’s turnaround record of just 27 days and has completed eight orbital-class launches in 12 months, averaging one flight every ~45 days – an average turnaround time that’s better than the Space Shuttle’s all-time record. (SpaceX)

While Dragon and Falcon 9 are far smaller than Starship and Super Heavy, Dragon is only partially reusable and requires significant refurbishment after recovery and Falcon 9 boosters are fairly complex. Starship, on the other hand, should effectively serve as a fully reusable all-in-one Falcon upper stage, Dragon capsule, Dragon trunk, and fairing, making it far more complex but potentially far more reusable. To an extent, Super Heavy should also be mechanically simpler than Falcon boosters (no deployable legs or fins; no structural composite-metal joints; no dedicated maneuvering thrusters) and its clean-burning Raptor engines should be easier to reuse than Falcon’s Merlins. Put simply, there are precedents set and evidence provided by Falcon rockets and NASA’s Space Shuttle that suggest SpaceX will be able to solve the reusability half of the equation.

What about refueling?

The other half of that equation, however, could not be more different. The sum total of SpaceX’s official discussions of orbital refueling can be summed up in a sentence included verbatim in CEO Elon Musk’s 2017, 2018, and 2019 Starship presentations: “propellant settled by milli G acceleration using control thrusters.”

This phrase first appeared in 2017 (PDF; page 16). (SpaceX)

On the face of it, that simple phrase doesn’t reveal much. However, with a few grains of salt, hints from what the company’s CEO has and hasn’t said, and context from the history of research into orbital propellant transfer, it’s possible to paint a fairly detailed picture of the exact mechanisms SpaceX will likely use to refill Starships in space. The cornerstone, somewhat ironically, is a 2006 paper – written by seven Lockheed Martin employees and a NASA engineer – titled “Settled Cryogenic Propellant Transfer.” Aside from the obvious corollaries just from the title alone, the paper focuses on what the authors argue is the simplest possible route to large-scale orbital propellant transfer.

In orbit, under microgravity conditions, the propellant inside a spacecraft’s tanks is effectively detached from the structure. If a spacecraft applies thrust, that propellant will stay still until it splashes against its tank walls – the most basic Newtonian principle that objects at rest tend to stay at rest. If, say, a spacecraft thrusts in one direction and opens a hatch or valve on the tank in the opposite direction of that thrust, the propellant inside it – attempting to stay at rest – will naturally escape out of that opening. Thus, if a spacecraft in need of fuel docks with a tanker, their tanks are connected and opened, and the tanker attempts to accelerate away from the receiving ship, the propellant in the tanker’s tanks will effectively be pushed into the second ship as it tries to stay at rest.

The principles behind such a ‘settled propellant transfer’ are fairly simple and intuitive. The crucial question is how much acceleration the process requires and how expensive that continuous acceleration ends up being. According to Kutter et al’s 2006 paper, the answer is surprising: assuming a 100 metric ton (~220,000 lb) spacecraft pair accelerates at 0.0001G (one ten-thousandth of Earth gravity) to transfer propellant, they would need to consume just 45 kg (100 lb) of hydrogen and oxygen propellant per hour to maintain that acceleration.

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Two possible Starship orientations for propellant transfer. (SpaceX)

In the most extreme hypothetical refueling scenario (i.e. a completely full tanker refueling a ship with a full cargo bay), two docked Starships would weigh closer to 1600 tons (~3.5M lb) and the “Milli G” acceleration SpaceX has repeatedly mentioned in presentation slides would be ten times greater than the maximum acceleration analyzed by Kutter et al. Still, according to their paper, that propellant cost scales linearly both with the required acceleration and with the mass of the system. Roughly speaking, using the same assumptions, that means that the thrusting Starship would theoretically consume just over 7 tons (half a percent) of its methane and oxygen propellant per hour to maintain milli-G acceleration.

With large enough pipes (on the order of 20-50 cm or 8-20 in) connecting each Starship’s tanks, SpaceX should have no trouble transferring 1000+ tons of propellant in a handful of hours. Ultimately, that means that settled propellant transfer even at the scale of Starship should incur a performance ‘tax’ of no more than 20-50 tons of propellant per refueling. All transfers leading up to the worst-case 1600-ton scenario should also be substantially more efficient. Overall, that means that fully refueling an orbiting Starship or depot with ~1200 tons of propellant – requiring anywhere from 8 to 14+ tanker launches – should be surprisingly efficient, with perhaps 80% or more of the propellant launched remaining usable by the end of the process.

On Super Heavy B4, SpaceX has installed what amount to nozzles over the booster’s main oxygen tank vents to vector and maximize the thrust they produce. (NASASpaceflight – bocachicagal)

A step further, Kutter et al note the amount of acceleration required is so small that a hypothetical spacecraft could potentially use ullage gas vents to achieve it, meaning that custom-designed settling thrusters might not even be needed. Coincidentally or not, SpaceX (or CEO Elon Musk) has recently decided to use strategically located ullage vents to replace purpose-built maneuvering thrusters on Starship’s Super Heavy booster. If SpaceX adds similar capabilities to Starship, it’s quite possible that the combination of cryogenic propellant naturally boiling into gas as it warms and the ullage vents used to relieve that added pressure could produce enough thrust to transfer large volumes of propellant.

Last but not least, writing more than a decade and a half ago, the only technological barrier Kutter et al could foresee to large-scale settled propellant transfer wasn’t even related to refueling but, rather, to the ability to autonomously rendezvous and dock in orbit. In 2006, while Russia was already routinely using autonomous docking and rendezvous technology on its Soyuz and Progress spacecraft, the US had never demonstrated the technology on its own. Jump to today and SpaceX Dragon spacecraft have autonomously rendezvoused with the International Space Station twenty seven times in nine years and completed ten autonomous dockings – all without issue – since 2019.

SpaceX has already developed and thoroughly tested hot-gas Raptor-derived maneuvering thrusters that could be fairly easily added to Starship to boost the efficiency of settled propellant transfer at the cost of added weight and complexity. (NASASpaceflight – bocachicagal)

Even though SpaceX and its executives have never detailed their approach to refueling (or refilling, per Musk’s preferred term) Starships in space, there is a clear path established by decades of NASA and industry research. What little evidence is available suggests that that path is the same one SpaceX has chosen to travel. Ultimately, the key takeaway from that research and SpaceX’s apparent use of it should be this: while a relatively inefficient process, SpaceX has effectively already solved the last remaining technical hurdle for settled propellant transfer and should be able to easily refuel Starships in orbit with little to no major development required.

There’s a good chance that minor to moderate problems will be discovered and need to be solved once SpaceX begins to test refueling in orbit but crucially, there are no obvious showstoppers standing between SpaceX and the start of those flight tests. Aside from the obvious (preparing a new rocket for its first flight tests), the only major refueling problem SpaceX arguably needs to solve is the umbilical ports and docking mechanisms that will enable propellant transfer. SpaceX will also need to settle on a location for those ports/mechanisms and decide whether to implement ullage vent ‘thrusters’, cold gas thrusters like those on Falcon and current Starship prototypes, or more efficient hot-gas thrusters derived from Raptors. At the end of the day, though, those are all solved problems and just a matter of complex but routine systems engineering that SpaceX is an expert at.

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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 Full Self-Driving v14.3 rolls out: here’s what’s new

We are in EAP and will be on the road with v14.3 in the coming hours, so we’ll have a lot of things to discuss over the next few days, especially coming from v14.2.2.5, which I called the most “confusing” FSD release of all time.

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2 hours ago

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April 7, 2026

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Tesla has officially started rolling out Full Self-Driving v14.3 to Early Access Program (EAP) members, and there are a lot of new improvements.

We are in EAP and will be on the road with v14.3 in the coming hours, so we’ll have a lot of things to discuss over the next few days, especially coming from v14.2.2.5, which I called the most “confusing” FSD release of all time.

Tesla brought out a lot of improvements, according to the v14.3 release notes, which list a vast number of fixes, new features, and new capabilities.

Here’s what Tesla’s release notes for the v14.3 release state:

  • Improved parking location pin prediction, now shown on a map with a P icon.
  •  Increased decisiveness of parking spot selection and maneuvering.
  • Rewrote the Al compiler and runtime from the ground up with MLIR, resulting in 20% faster reaction time and improving model iteration speed.
  • Enhanced response to emergency vehicles, school buses, right-of-way violators, and other rare vehicles.
  • Mitigated unnecessary lane biasing and minor tailgating behaviors.
  • Improved handling of small animals by focusing RL training on harder examples and adding rewards for better proactive safety.
  • Improved traffic light handling at complex intersections with compound lights, curved roads, and yellow light stopping – driven by training on hard RL examples sourced from the Tesla fleet.
  • Upgraded the Reinforcement Learning (RL) stage of training the FSD neural network, resulting in improvements in a wide variety of driving scenarios.
  • Upgraded the neural network vision encoder, improving understanding in rare and low-visibility scenarios, strengthening 3D geometry understanding, and expanding traffic sign understanding.
  • Improved handling for rare and unusual objects extending, hanging, or leaning into the vehicle path by sourcing infrequent events from the fleet.
  • Improved handling of temporary system degradations by maintaining control and automatically recovering without driver intervention, reducing unnecessary disengagements.

Tesla also listed a handful of future improvements as well:

  • Expand reasoning to all behaviors beyond destination handling
  • Add pothole avoidance
  • Improve driver monitoring system sensitivity with better eye gaze tracking, eye wear handling, and higher accuracy in variable lighting situations

CEO Elon Musk has said that v14.3 could be “where the last big piece of the puzzle finally lands.” We have high expectations for this release because, in a lot of ways, v14.2’s final version was extremely disappointing and seemed to be a regression more than anything.

Nevertheless, Full Self-Driving v14.3 is going to be quite an interesting test, considering this is also the first time Musk has stated it will feel like the car will be “sentient.”

Reasoning will be a bigger piece of the puzzle with this release, although there were some elements of it in v14.2.

Tesla AI Head says future FSD feature has already partially shipped

We plan to travel plenty of miles with it over the next few days, so we’ll keep you posted on what our thoughts are.

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Tesla Model Y ownership review after six months: What I love and what I don’t

I pay about $25 more a month than I did for my Bronco Sport for my Tesla. It was a no-brainer to switch. Like any car, it isn’t perfect, but my Tesla has more things right than any other car I’ve owned, and that makes it truly incredible.

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6 hours ago

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April 7, 2026

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Credit: Joey Klender

It has been just over six months since I took delivery of my Diamond Black Tesla Model Y Premium Long Range (at that time, it was called the Tesla Model Y Long Range All-Wheel-Drive).

In those six months, I have had the opportunity to experience true and pure electric vehicle ownership, what comes with it after driving a gas vehicle for my entire life, and, to be completely frank, there are not many things I would change.

Owning a Tesla was something I never thought I’d do until I owned a house, simply to take advantage of the advantage of home charging. However, I had to take the chance last year with the elimination of the $7,500 electric vehicle tax credit, as well as to avoid the mountainous stack of repair bills that were presenting themselves with my Ford Bronco Sport.

There are a lot of things I love about my Model Y, and there are a handful of things I wish I could change. In this piece, I plan to break down the ownership experience through about six months with my Tesla Model Y, hoping to provide you with enough insight to potentially make a change — or stick with what you have.

Things I Love About My Tesla Model Y

Driving Experience

Tesla really pushes Full Self-Driving and autonomy, but there are times that, as an owner, I feel I need to drive this car manually. Tesla put so much effort into the Model Y’s engineering and driving experience that it feels like a bit of a disservice to have it drive itself around all the time.

The suspension in this vehicle, as well as its ability to handle sharp corners, its quick acceleration, and its ability to hug the road at spirited speeds, is truly something you need to feel for yourself. I personally have never had a car that was truly geared toward driving this way. Other than a short-lived ownership experience with a Honda Civic a few years back (something I won’t ever do again), all of my vehicles have been SUVs or compact crossovers.

Credit: Joey Klender

Having a car that offers both a fun driving experience and cargo space is what the Model Y truly is all about. It’s a fun car to drive, but it also has a lot of functionality.

It is always a treat when it’s a little warmer out, I can roll the windows down, and take my Model Y to a tight back road in Pennsylvania to have some fun. I have never loved driving in the traditional sense. I don’t hate it, but it’s not necessarily “fun” to me, but that’s probably because I never had a car that was engineered to make the driving experience enjoyable.

This has truly changed my perspective on driving, and the Model Y is probably the second-most-fun car I’ve ever had the pleasure of driving. The first? The Tesla Model S.

Home Charging and Supercharging

Now, Home Charging is relatively new to me, and I covered my process for figuring that out in another article, which is linked here.

Waking up in the morning and having some additional range is really a great feeling — and with gas prices going through the stratosphere, the money I’m saving on gas is something quite special.

Supercharging is also a fun experience for me. Do I wish it were a faster experience? Sure. But there’s plenty to do in the car: Netflix, Hulu, Tesla Arcade, or head into whatever convenience store is nearby, use the restroom, and grab a bite to eat.

I have come to enjoy the evenings that I’ll head over to the Supercharger and plug my car in for half an hour before a longer drive the next day (if I didn’t plug in soon enough at home and need some fast-charging).

Tesla also added a new Supercharging “Wrapped” feature at the end of the year, gamifying the entire Supercharging experience. I’m excited to see all the places I’ve charged at the end of 2026.

Sporty, Clean, and Fun Interior

The interior of my Tesla is probably one of the most underrated features of my car, but it’s definitely my favorite. With vehicles I’ve purchased in the past, the big selling point is the inside for me, not the outside. Of course, I want my car to look good to others, but ultimately, I’m paying the payment and I’m spending 100% of the time I’m using the car on the inside of it.

This highlights the need for a comfy, cozy, and capable cabin that has all the features I could want. In Pennsylvania, we have cold winters and hot and humid summers. The Model Y has heated seats and a steering wheel, as well as A/C seats. The HVAC is incredibly capable, customizable, and comfortable for all passengers, allowing them to make adjustments wherever needed.

At night, the black interior coupled with the accent lighting makes for one of the coolest, spaceship-like interiors on the market. Tesla always called it a “Rave Cave,” and it truly feels like it.

Tech: From Full Self-Driving to Other Features

Tech is really the biggest part of owning a Tesla; it is so advanced that it almost feels like it’s not even a car. Full Self-Driving is obviously such a huge advantage, and I’ve talked about it in great detail, both positively and negatively.

I could write 1,000 words on FSD, but I don’t want to focus on it solely, because there are so many other things that need to be highlighted.

One thing Tesla really has over others is the ability to improve its cars continually. Simple features like a charging adjustment, new modes, or activating features that weren’t quite ready previously are all things Tesla has added through Over-the-Air updates.

I don’t know if I could pick just one as a favorite, but in the six months I’ve had my car, the most useful thing I’ve come across outside of FSD is Summon. While it is hit or miss a lot of the time, there are little features, like moving the car forward or back from the Tesla App, that are incredibly useful. Adjusting a park job, making snow shoveling around the car easier, or even moving the car slightly when I’m taking photos or video is incredibly seamless with this functionality.

Cargo and Interior Space

One of my big concerns when going from a Bronco Sport to a Model Y was cargo space, only to find out the Model Y has more space than the Bronco Sport. I always have something in the trunk, whether it is luggage, my golf bag, shoes, or groceries. I’ve never felt like I’ve needed more space in this car, although I’m sure that day will come when I get the boys together for a golf trip and I am driving.

I’ve packed luggage for my Fiancèe and a few of her friends on a trip to Disney with no issues. Four girls going to Disney for five days is a challenge that will frighten even the most capable vehicles. I had no issues.

But what is also great about the Model Y is that it has the room to do other things, like fit an entire mattress for camping. SNUUZU makes an amazing Tesla mattress that I have thrown in the car to watch sunsets. This Summer, I’ll do some camping with it.

It’s one of the many things about this car that I really love.

Things About My Tesla Model Y I Do Not Love

Winter Range

There’s no getting around the fact that owning this car without a faster charging option at home in the winter is truly frustrating. I was charging much more frequently in January and February than in any other month.

I took a 40-mile round-trip drive to grab some hot wings with friends in January. It took about 105 miles of range.

The cold weather was truly a frustrating time to own an EV, and my problems would have been solved with a Level 2 charger at home. Even still, the drives that were a few hours long were going to be fit with 10-15 minute stops to grab some range at a Supercharger.

Navigation

I really think that Tesla could have the best navigation out there. They always talk about licensing FSD, but if they were to license their Navigation software, I think it could overtake Apple Maps, Waze, and others. With a weather radar, live traffic updates, satellite imagery, and more, the Navigation system is truly the best around.

However, the Navigation itself, meaning the routing, is absolutely abysmal. It doesn’t learn from mistakes, it doesn’t learn more ideal routing, and it doesn’t seem to improve at any point. It still tries to leave my neighborhood by turning left out of a right-turn-only exit. It routinely takes some of the most head-scratching routes to local destinations.

Consistently using the FSD disengage feature to report the problems to Tesla’s AI Team doesn’t seem to yield much of a result. It would be great if there were a “Learn” mode so that it could be less on Tesla to refine things, and the car would just learn automatically.

Cup Holders

This is a really trivial and nitpicky point of criticism, but boy, do these cupholders need to be larger. Many of my reusable water bottles do not fit in them, so I had to grab a $25 cup holder “adapter” from Amazon. It obstructs the center console from opening comfortably, but it is what it is. It fits standard cups, soft drink containers from fast food restaurants, and bottles of water, at least for the most part.

It would be nice if Tesla could think about something for the next Model Y refresh here, although I may be the only one to really complain about them.

Final Thoughts

I pay about $25 more a month than I did for my Bronco Sport for my Tesla. It was a no-brainer to switch. Like any car, it isn’t perfect, but my Tesla has more things right than any other car I’ve owned, and that makes it truly incredible.

Sometimes I am still baffled that this is my car. It feels crazy to drive something that is so far ahead of any other car I’ve driven. Three of my friends own Teslas now, all of us bought them at the same time last year, and all four of us don’t know if we’d ever consider going back.

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Elon Musk’s Terafab project locks up massive new partner

Terafab, first revealed by Musk in March, is a massive joint-venture semiconductor complex planned for the North Campus of Giga Texas in Austin.

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8 hours ago

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April 7, 2026

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Credit: SpaceX

Elon Musk’s Terafab project just locked up a massive new partner, just weeks after the new project was announced by Tesla, SpaceX, and xAI, the three companies that will be direct benefactors from it.

In a landmark announcement on April 7, Intel joined Elon Musk’s Terafab project as a key partner alongside Tesla, SpaceX, and xAI. The collaboration focuses on refactoring silicon fabrication technology to deliver ultra-high-performance chips at unprecedented scale.

Intel CEO Lip-Bu Tan hosted Musk at Intel facilities the prior weekend, underscoring the partnership’s momentum with a public handshake.

Terafab, first revealed by Musk in March, is a massive joint-venture semiconductor complex planned for the North Campus of Giga Texas in Austin. Valued at $20–25 billion, it aims to consolidate the entire chip-making pipeline, design, fabrication, memory production, and advanced packaging in a single location. It should eliminate a majority of Tesla’s dependence on third-party chip fab companies.

The facility will manufacture two primary chip types: energy-efficient edge-inference processors optimized for Tesla’s Full Self-Driving (FSD) systems, Cybercab and Robotaxi, and Optimus humanoid robots, and high-power, radiation-hardened variants for SpaceX satellites and xAI’s orbital data centers.

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

The project’s audacious goal is to produce 1 terawatt (TW) of annual compute capacity, roughly 50 times current global AI chip output.

Production is expected to begin modestly and scale rapidly, addressing Musk’s warning that chip supply could soon become the biggest constraint on Tesla, SpaceX, and xAI growth. By vertically integrating manufacturing tailored to their exact needs, Terafab eliminates supply-chain bottlenecks and accelerates iteration for AI training, inference at the edge, and space-based computing.

Intel’s participation is strategically vital. The company will contribute expertise in advanced process technology, high-volume fabrication, and packaging to help Terafab achieve its aggressive targets. For Intel, the deal strengthens its foundry business and positions it as a critical U.S. player in the AI hardware race.

For Musk’s ecosystem, it secures domestic, purpose-built silicon at a time when global capacity meets only a fraction of projected demand for hundreds of millions of robots and orbital AI infrastructure.

This is the latest chapter in Intel-Tesla ties. In November 2025, Musk publicly stated at Tesla’s shareholder meeting that partnering with Intel on AI5 chips was “worth having discussions,” amid concerns about TSMC and Samsung capacity.

Exploratory talks followed, with Intel eyeing custom-AI opportunities. The Terafab integration transforms those conversations into concrete collaboration.

The Intel-Terafab alliance carries broader implications. It bolsters U.S. semiconductor sovereignty, drives innovation in cost- and power-efficient AI silicon, and supports Musk’s vision of exponential progress in autonomy, robotics, and space.

As AI compute demand surges, this partnership could reshape the industry, delivering the silicon backbone for a new era of intelligent machines on Earth and beyond.

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