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SpaceX’s Starship Raptor Vacuum engine plans laid out by CEO Elon Musk

A 2016 render of Raptor Vacuum. Much has changed about the engine's design in the three years since, but SpaceX is still pursuing a vacuum variant. (SpaceX)

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Elon Musk says that SpaceX Starship engine upgrades are on track to begin static fire tests of a Raptor Vacuum variant as few as a “couple months” from now.

Designed to enable more efficient performance in thin atmosphere or vacuum, Musk admitted that the first version(s) of Raptor Vacuum (RVac) will likely be a compromise between efficiency and speed of development. Nevertheless, the faster SpaceX can prepare Raptor Vacuum for flight, the easier it will be for Starship to begin serious (sub)orbital flight tests.

As it turns out, SpaceX’s first and only official render of Raptor – published in September 2016 – showed the engine’s vacuum-optimized variant. In the years since, CEO Elon Musk has vacillated between keeping the vacuum engines as a central Starship feature and simply replacing them with regular sea level Raptors to expedite the spacecraft’s debut. The 2016 and 2017 vehicles featured a mixture of vacuum and sea-level engines, whereas Musk revealed a vehicle with sea-level engines only in 2018.

Known as the Interplanetary Transport System in 2016, the ship featured six vacuum Raptors and 3 SL engines. (SpaceX)
In 2017, Big Falcon Spaceship shrunk and changed to 4 x RVac and 3x x Raptor SL engines. (SpaceX)
In 2018, Musk decided to sidestep vacuum engines entirely, moving to 7 SL Raptors. (SpaceX)

Perhaps less than a month after Musk’s September 2018 presentation, the SpaceX CEO made the decision to radically redesign the vehicle – newly christened Starship and Super Heavy – by moving from a carbon composite aerostructure to stainless steel. At first, the seven SL Raptors remained a part of the design, but Musk took to Twitter in 2019 to indicate that SpaceX had changed gears again and had reprioritized Raptor Vacuum development.

This came as a bit of surprise and it should go without saying that there’s a significant chance that Musk/SpaceX will oscillate in the opposite direction once again before Raptor Vacuum is actually ready for flight. This time, though, Musk has sketched out a development schedule and strategy that suggests SpaceX is much more serious this time.

Most notably, Musk claims that the first Raptor Vacuum prototype could be ready for static fire testing just a “couple months” from now, an immensely ambitious schedule for any large liquid rocket engine development program. Nevertheless, Musk did indicate that the “V1.0” Raptor Vacuum design would be significantly compromised and “suboptimal”, an intentional decision to prioritize the engine’s “speed of development”.

Even then, Musk believes that the first variant – featuring a shortened bell nozzle – could still be up to 12% more efficient than sea level Raptors and thus already 70-80% of the way to the physical limit of methane-oxygen rocket efficiency.

A sea-level Raptor engine is static-fired at SpaceX’s McGregor, TX test facilities. (SpaceX)

On a positive note, shrinking V1.0 Raptor Vacuum’s nozzle a bit from its nominal length will likely mean that SpaceX can static fire fully-integrated engines at its McGregor, TX test facilities, critical for speedy development. If not, the company has experience with alternatives through Merlin Vacuum, which can only be tested on the ground with its lengthy nozzle detached. This method just makes it dramatically harder to optimize a vacuum nozzle design, as full-scale, flight-like testing is nearly impossible if a given vacuum engine can’t be tested on the ground with said nozzle installed.

Vacuum engines need such large and unwieldy nozzles in order to make them as efficient as possible. In a very simplistic sense, a rocket engine nozzle directs the flow of superheated, ultrafast gases in order to squeeze as much momentum transfer as possible out of available propellant. The lower the pressure of the surrounding atmosphere is, the more those gases will expand immediately after leaving the nozzle – giant vacuum nozzles simply try to harness the additional momentum available from that extra expansion. This is why rocket exhausts appear to spread and thin out as launch vehicles reach higher and higher altitudes.

A Falcon 9 upper stage’s vacuum nozzle glows white hot during an orbital MVac burn. (SpaceX)

In this sense, the perfect theoretical vacuum nozzle is quite literally infinitely long. The job of vacuum rocket engineers is to find the perfect balance between that impractical theoretical perfection and the limits of real-world materials and dynamics. In theory, SpaceX’s sea-level Raptor engines have already been designed to operate in vacuum conditions, while the engine’s closed-cycle design and regeneratively (i.e. propellant) cooled nozzle should apply well to a vacuum design.

If SpaceX is lucky, there will be few roadblocks in the way of simply lengthening a SL Raptor-style nozzle and calling it a day, in which case it would be impressive but not all that surprising if SpaceX is actually able to begin RVac testing before the end of 2019. Once a rough V1.0 engine is in place, the process of optimizing efficiency can be done slowly and methodically, all while exploiting an unprecedented wealth of data from flight and orbit-tested Raptor Vacuum engines.

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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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Grok Bot users hit with weekly limits early, Elon Musk explains what happened

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Credit: Grok Bot

Elon Musk said weeks ago during SpaceX’s third-quarter earnings call that the company’s Grok Bot, its autonomous AI Agent platform, was showing “the fastest growth of a product” that he’d ever seen in his life.

Now, SpaceXSI is scaling back Grok Bot users’ weekly limits, much to the surprise of those who have relied on it to take away monotonous tasks in their lives.

Elon Musk’s terse November 1 reply on X captured a sharp tension in the early days of agentic AI. Responding to a user who asked for a Grok Bot usage reset after hitting 100 percent with four days still left on the weekly cycle, Musk wrote: “The cost of serving Grok Bot was unsustainably high relative to revenue.”

The post arrived amid a wave of similar complaints from paying subscribers whose meters had jumped unexpectedly toward or to the limit, sometimes overnight and with little corresponding activity. It also stood in clear contrast to statements Musk had made only days and weeks earlier.

On the SpaceX third-quarter earnings call in mid-to-late October, Musk had described Grok Bot in almost the opposite terms. He called it “the fastest growth of a product that I’ve ever seen in my life” and said he had “never seen anything grow this fast.”

Company figures put paid weekly users at roughly 800,000 earlier in the month, more than doubling over the prior period. Daily active users had climbed from under 100,000 in early September to over 600,000 by late October.

Musk emphasized that the product has no free tier and that users appear to be getting real value beyond what they pay. In other remarks, he noted that usage per user was rising rather than declining, the opposite of the usual decay pattern for new software.

Grok Bot, launched around August, functions as an always-available agent with its own persistent cloud computer; it can schedule, research, shop, browse, and execute multi-step workflows even after the user steps away. Access is bundled into X subscription tiers (roughly $30, $100, and $200 per month) and certain Cursor plans, drawing from shared weekly usage pools whose exact sizes have not been publicly detailed.

The economics of that model are what Musk’s November 1 post put in the spotlight. Agentic systems burn far more compute than ordinary chatbot exchanges. Each task can trigger repeated model calls, tool use, web actions, and sustained background work.

When growth is as rapid as Musk celebrated, the absolute compute bill scales quickly even if average revenue per user stays fixed under flat monthly subscriptions. Industry observers noted the opportunity cost as well: the same GPUs can be rented to other AI labs at higher rates.

A simple back-of-the-envelope comparison circulating after the post illustrated the gap: if every reported daily user paid the top tier, annualized subscription revenue would still be modest relative to the scale of compute infrastructure SpaceX is building and leasing to companies like Anthropic.

Some users also reported possible dashboard anomalies around the same period, though Musk’s framing treated the underlying cost-revenue imbalance as the core issue rather than a pure metering glitch.

The juxtaposition is the core of this exchange. Within roughly two weeks of publicly framing Grok Bot as an unprecedented success with strong unit economics and no free tier, Musk acknowledged that serving the same product had become unsustainable relative to the revenue it generates.

For the broader industry, the episode underscores a structural challenge of the agent era: demand is real and growing faster than many expected, yet the cost of fulfilling that demand through always-on, multi-step agents can outrun subscription pricing before companies can adjust limits, introduce metered billing, or raise prices.

Musk’s reply did not promise an immediate reset or higher allowances; it simply stated the constraint. In doing so, it supplied a rare, explicit public data point on the unit economics of a high-profile AI agent just as adoption numbers were still being celebrated as the fastest in Musk’s experience.

The tension between rapid, paid growth and the compute required to deliver it is now on the record.

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Tesla owners who tap Emergency Drive Away for fun are in for a surprise

Tapping Activate on Tesla’s Emergency Drive Away reportedly triggers a $539 service bill without moving.

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Tesla owners who press Activate on Emergency Drive Away may be on the hook for a service bill even if their car never leaves the Supercharger stall.

Yaro, who posts about Tesla service cases on X as @Tutrifour, said a customer called after tapping Activate while still plugged into a Supercharger. The owner was about to pull away, remembered the cable was still connected and stopped. The car never moved, but the touchscreen showed a red alert reading “Emergency Drive Away has been activated” with “Service is required” underneath. A Service Mode screenshot showed the active alert BMS_a228_EmergencyDriveAwayServiceRequired, which Yaro said only Tesla Service can clear.


The cost of clearing it was the bigger surprise. “Don’t press Activate on the new Emergency Drive Away feature on your Tesla because service charges $539 to inspect the charge port and to clear the alert. Yes, even if you didn’t move the car an inch,” Yaro wrote.  The $539 figure comes from that single case, and Tesla has not published a set price for the inspection or commented on the post. Yaro also noted that the car would still charge with the alert on screen.

Tesla launched Emergency Drive Away on October 1 with software update 2026.38.3, letting drivers pull away from a U.S. Supercharger with the cable still attached, as Teslarati reported. To use it, a driver shifts into Drive while connected, holds the brake and taps Activate. The prompt warns that driving with the cable connected will damage the vehicle and the Supercharger, and that short camera recordings will be shared with Tesla.

Tesla Charging has been clear about what follows a real activation. Repairs to a Supercharger stall can run up to $25,000 depending on the site, a service visit for the car’s charge port is mandatory, and deliberate misuse “will invoke additional penalties.” What the company had not spelled out is that the service requirement is triggered the moment Activate is pressed, not the moment the cable breaks away.

From an engineering standpoint, that is the cautious choice. Once Activate is pressed, the car cannot be sure the charge port latch was not stressed, so flagging it for inspection removes the guesswork. It also means the button carries a price on its own, which is a stronger deterrent against casual use than any warning screen.


The report follows the feature’s first known real world use, when a driver in Austin during F1 weekend appeared to trigger it by accident and dragged the Supercharger cable along with the car. The Reddit user who filmed it said the driver seemed to have only half read the prompts.

For owners, the takeaway is to treat the red prompt as a stop sign. If it appears after shifting out of Park by mistake, shift back and unplug the normal way from the touchscreen, the Tesla app or the button on the charge handle. Activate is meant for moments when staying at the stall is the bigger risk, and Tesla is now pricing it that way.

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Elon Musk calls Earth’s data centers “peanuts” next to what SpaceX is planning in orbit

Elon Musk says SpaceX capex efficiency is underestimated as orbital data centers loom by 2028.

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Elon Musk is pushing back on one of the biggest worries hanging over SpaceX stock. In a reply on X on Sunday, Musk said the company’s capital expenditure efficiency is severely underestimated. He was responding to a Milk Road Stocks post citing analyst Kyle Reidhead, who estimates SpaceX will need to spend roughly $470 billion over the next five quarters.

Reidhead built that figure around the target SpaceX set on its third quarter earnings call: 13 gigawatts or more of compute by the end of 2027. In his breakdown, Nvidia captures 83 to 89 percent of the spending. SpaceX ended the quarter with 1.7 GW of nameplate compute and guided to $35 billion to $40 billion in fourth quarter capex, as Teslarati reported.

Musk did not attach a number to his claim, but the earnings call shows the argument. CFO Bret Johnsen said new compute currently pays for itself in under a year at today’s pricing, and Musk said that window could shrink to six months next year. Using that pace, Reidhead argues about $230 billion of the $470 billion could come from operating cash flow and about $60 billion from SpaceX’s roughly $90 billion cash pile, leaving around $180 billion to borrow. Musk confirmed last week that SpaceX had already closed a new $40 billion debt raise to buy GPUs.

The ground buildout is not the end goal. It is what is meant to pay for the move to orbit. Replying on Friday to charts built from Sequoia partner Shaun Maguire’s SpaceX model, Musk wrote that “Terrestrial compute will be peanuts compared to orbital compute,” adding that orbital compute deployed per month “probably exceeds terrestrial around the end of 2028 and then far exceeds it in 2029.”

Maguire’s model shows how steep that path is. It has capex climbing from $88 billion this year to $290 billion in 2027 and $369 billion in 2028, with SpaceX burning $77.8 billion in cash this year and $122.6 billion next year before turning $114.9 billion cash positive in 2028. Musk’s response to the model was, “I think we can do better.”

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The orbital half runs through Starmind. SpaceX plans to operate up to 1 million AI satellites flying in clusters of about 10, linked by roughly 10 terabits of bandwidth, with deployment of thousands of units starting as soon as late 2027 out of its Gigasat factory in Bastrop, Texas, according to SpaceX’s space safety page. Musk has said each Starmind spacecraft will carry more than 250 kW of solar power.

Getting there depends on launch volume. Maguire’s model assumes 250 Starship flights in 2028, up from two this year and 38 next year. The nearer test is financial: SpaceX guided to $33 billion to $37 billion in first quarter 2027 revenue, more than double the $14.58 billion it booked in Q3, and Musk reposted that guidance again on Sunday morning.

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