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


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.”

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.


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.


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.

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.
Investor's Corner
Tesla enters new stability phase, firm upgrades and adjusts outlook
Dmitriy Pozdnyakov of Freedom Capital upgraded his outlook on Tesla shares from “Sell” to “Hold” on Wednesday, and increased the price target from $338 to $406.
Tesla is entering a new phase of stability in terms of vehicle deliveries, one firm wrote in a new note during the final week of October, backing its position with an upgrade and price target increase on the stock.
Dmitriy Pozdnyakov of Freedom Capital upgraded his outlook on Tesla shares from “Sell” to “Hold” on Wednesday, and increased the price target from $338 to $406.
While most firms are interested in highlighting Tesla’s future growth, which will be catalyzed mostly by the advent of self-driving vehicles, autonomy, and the company’s all-in mentality on AI and robotics, Pozdnyakov is solely focusing on vehicle deliveries.
The analyst wrote in a note to investors that he believes Tesla’s updated vehicle lineup, which includes its new affordable “Standard” trims of the Model 3 and Model Y, is going to stabilize the company’s delivery volumes and return the company to annual growth.
Tesla launches two new affordable models with ‘Standard’ Model 3, Y offerings
Tesla launched the new affordable Model 3 and Model Y “Standard” trims on October 7, which introduced two stripped-down, less premium versions of the all-electric sedan and crossover.
They are both priced at under $40,000, with the Model 3 at $37,990 and the Model Y at $39,990, and while these prices may not necessarily be what consumers were expecting, they are well under what Kelley Blue Book said was the average new car transaction price for September, which swelled above $50,000.
Despite the rollout of these two new models, it is interesting to hear that a Wall Street firm would think that Tesla is going to return to more stable delivery figures and potentially enter a new growth phase.
Many Wall Street firms have been more focused on AI, Robotics, and Tesla’s self-driving project, which are the more prevalent things that will drive investor growth over the next few years.
Wedbush’s Dan Ives, for example, tends to focus on the company’s prowess in AI and self-driving. However, he did touch on vehicle deliveries in the coming years in a recent note.
Ives said in a note on October 2:
“While EV demand is expected to fall with the EV tax credit expiration, this was a great bounce-back quarter for TSLA to lay the groundwork for deliveries moving forward, but there is still work to do to gain further ground from a delivery perspective.”
Tesla has some things to figure out before it can truly consider guaranteed stability from a delivery standpoint. Initially, the next two quarters will be a crucial way to determine demand without the $7,500 EV tax credit. It will also begin to figure out if its new affordable models are attractive enough at their current price point to win over consumers.
Elon Musk
Tesla preps for a harsh potential reality if Musk comp vote doesn’t go to plan
A successful vote for Tesla would see the compensation package get approved. But there is always the possibility of a rejection, which would likely see Musk leave the company.
Tesla could be forced to look for a new CEO in the coming months, as a crucial November 6 Shareholder Meeting vote will determine whether Elon Musk will stick around.
A major vote is coming up at the 2025 Tesla Shareholder Meeting, as investors will determine whether Musk should be given a new compensation plan that would award him up to $1 trillion and more than one-fourth of the total voting power within the company.
Tesla board chair reiterates widely unmentioned point of Musk comp plan
A successful vote for Tesla would see the compensation package get approved. But there is always the possibility of a rejection, which would likely see Musk leave the company.
“My fundamental concern with regard to how much voting control I have at Tesla is if I go ahead and build this enormous robot army, can I just be ousted at some point in the future? That’s my biggest concern,” Musk said at last week’s Earnings Call. “That’s what it comes down to in a nutshell. I don’t feel comfortable wielding that robot army if I don’t have at least a strong influence.”
Tesla Board of Directors Head Robyn Denholm has been on somewhat of a PR tour over the past few days, answering questions about the compensation plan, which is among the biggest issues currently for the company.
Denholm told Bloomberg yesterday that Tesla investors need to be prepared for Musk to abandon ship if the package is not approved, which brings on a new question: Who would take over the CEO role?
That is a question Denholm also answered yesterday, bringing forth the conclusion that Tesla would not look for an outside hire if Musk were to leave the company. Instead, it would promote someone internally.
The way it was reported by Bloomberg and Reuters seems to make it seem as if Tesla is preparing for the worst, as it states the company “is looking at internal CEO candidates,” not preparing to do so.
Of the executives at Tesla who immediately come to mind as ideal candidates for a potential takeover should Musk leave, Tesla China President Tom Zhu and Head of AI Ashok Elluswamy both come to mind. Zhu has monumental executive experience already, as he was appointed to the role of Senior VP of Automotive back in December 2022.
He then returned to China in 2024.
It seems Tesla wants to align its future, with or without Musk, on the same path that it is currently on, and internal candidates might have a better idea of what that looks like and truly means.
News
Tesla Full Self Driving (FSD) is nearing approval in a new country
As per the official, Tesla’s Full Self-Driving system could be enabled in Israel in the near future.
It appears that Tesla FSD (Supervised) is heading to a new country soon, at least based on comments from Israel’s Transport and Road Safety Minister Miri Regev.
As per the official, Tesla’s Full Self-Driving system could be enabled in Israel in the near future.
Israeli drivers are pushing for FSD rollout
While Tesla’s FSD is already operational in markets like the U.S., Canada, and Australia, Israeli owners have long been unable to use the feature due to regulatory barriers. Despite its premium price tag, however, numerous Tesla owners in Israel have noted that the technology’s safety benefits, at least when approved for real-world use in the country, justify its cost.
It was then no surprise that nearly 1,000 Tesla owners in Israel have already petitioned the government to greenlight FSD’s domestic release in Israel. In a post on X, Regev seemed to confirm that FSD is indeed coming to Israel. “I’ve received the many referrals from Tesla drivers in Israel! Tesla drivers? Soon you won’t need to hold the steering wheel,” she wrote in her post.
FSD’s regulatory support in Israel
Regev stated that her Ministry views promoting innovative technologies as essential to improving both road safety and smart mobility. A working group led by Moshe Ben-Zaken, Director General of the Ministry of Transportation has reportedly been tasked to finalize the approval process, coordinating with regulatory and safety agencies to ensure compliance with international standards.
In a comment to Geektime, Israel’s Ministry of Transportation and Road Safety noted that Regev is indeed supporting the release of FSD in the country. “Minister Regev sees great importance in promoting innovative technologies, and in particular in the entry of advanced driving systems (FSD) into the Israeli market, as part of the ministry’s policy to encourage innovation, safety, and smart transportation,” the Ministry stated.
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