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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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Investor's Corner

Tesla deliveries best Wall Street guesses alongside second-best energy quarter

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Credit: Tesla Europe & Middle East | X

Tesla (NASDAQ: TSLA) reported strong delivery figures that beat Wall Street guesses, and they were revealed alongside the company’s second-best quarter in terms of energy deployments ever.

Tesla announced this morning that it delivered 486,532 cars in Q3, while producing 464,391, exceeding analyst consensus, which sat around 462,000 units.

Meanwhile, Tesla reported 13.7 GWh of energy storage deployed for the quarter. That’s the second-best quarter Tesla has ever reported on that side of things.

Vehicle Deliveries

Deliveries were strong, and it was another quarter when Tesla had the opportunity to outshine the Wall Street pundits who are quick to criticize and slow to give credit. Tesla saw a slight decrease in deliveries compared to Q3 2025, but Tesla still had the $7,500 EV Tax Credit to use to help incentivize consumers to pick an EV.

A small decrease of 2.1 percent is pretty telling because it shows Tesla does not need massive federal credits to convince consumers to purchase its vehicles.

It was also the company’s third-best performance all-time in terms of deliveries, trailing that of Q3 2025 with 497,099 deliveries and Q4 2024, when the company handed over 495,570 cars.

We reported several days ago that Tesla Showrooms across the United States were completely bare of inventory or unclaimed units. Many locations also removed Demo Drive units, which had been bought by customers looking to take delivery sooner.

Tesla showrooms picked clean ahead of Q3 end as demand looks strong

Energy Generation

Tesla’s Energy Generation performance in Q3 was also very strong, as the company deployed 13.7 GWh of energy storage over the past three months. The only quarter when Tesla reported stronger energy deployment figures was Q4 2025, when 14.2 GWh of energy storage was deployed.

Tesla’s Q3 performance in energy generation has continued to grow each quarter, with the company increasing its deployments by ten-fold since Q3 2021, when just 1.3 GWh was deployed.

It is also nearly double what it was in Q3 2024, when the company reported 6.9 GWh. This is one of Tesla’s quickest-growing divisions, and it flies under the radar with fans and analysts, as many are focused on self-driving or the vehicles themselves.

Tesla Stock

Shares rose 5.07 percent to $372.06 at just after 10 a.m. on the East Coast. This is a rarity for Tesla after a strong delivery report, as positive news usually brings the stock down. Many quarters with extremely robust delivery reports have not been as kind to the Teslanaires of the world.

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Lifestyle

Tesla’s newest feature lets you floor it out of a Supercharger while plugged in

Tesla’s new Emergency Drive Away feature lets owners flee a Supercharger while still plugged in.

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Tesla has given drivers a way to escape while a vehicle is plugged-in at a Supercharger, in the event of an emergency. The company’s charging team announced a new feature on X called Emergency Drive Away, which lets a driver shift into Drive and pull away while the charging cable is still connected to the car.

Until now, a Tesla would not leave Park with a charge cable plugged in. Drivers had to release the latch from the touchscreen, the Tesla app, or the button on the charge handle, then wait for the port to let go. Emergency Drive Away removes that lockout, but Tesla is clear that it comes at a cost. “Use of this feature will damage your vehicle and the Supercharger,” the company wrote, adding that the function is meant for emergencies only and that deliberate misuse will lead to “additional penalties.” Tesla did not say what those penalties are.


The in-car prompt is just as direct, with the warning reading: “Driving with the cable connected will cause damage to your vehicle and the Supercharger. Short camera recordings will be shared with Tesla.” That footage gives Tesla a way to separate a real emergency from someone who simply did not want to wait for the latch.

The feature requires software update 2026.38.3, and Tesla said in replies to owners that it works at every Supercharger in the United States without new stall hardware. Model S and Model X vehicles built before 2021 are not supported, and the company says the feature applies to U.S. Superchargers “for now,” leaving Canada and other markets out at launch.

Tesla Supercharger argument leads to tragic shooting incident

Tesla did not tie the announcement to any specific event, but it arrives two months after a gunman opened fire at an In-N-Out in Twin Falls, Idaho, on August 1, targeting three people in two Teslas at the neighboring Supercharger. One of them, a 66 year old man from Salt Lake City, was killed. Superchargers have been the scene of violence before, including a fatal shooting at a station near Denver in 2023.

In the weeks after Twin Falls, owners pushed Tesla for a native way to escape a stall, and many pointed back to EVject, the aftermarket breakaway connector Tesla sued in 2024 over claims it lacked overtemperature protection. The two companies later reached an agreement that led EVject to recall its earlier connectors in favor of a version with thermal sensors.

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Elon Musk

Why Tesla Roadster unveiling delay might have nothing to do with it flying

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tesla roadster elon musk flying
Credit: Grok

Tesla announced on Monday that the Roadster event scheduled for today would be postponed due to the need for it to be held outside.

Less than 24 hours later, CEO Elon Musk broadened that by stating it was due to high winds, immediately sending everyone into a frenzy over the Roadster’s potential ability to fly.

And realistically, it could definitely have to do with it flying, hovering, or hopping; whatever Tesla has in mind for this demonstration could not be impacted by wind. However, it might have nothing to do with the vehicle flying whatsoever, and instead could be a simple precaution, as the Roadster is a very unique vehicle with some already official specs that are just mind-blowing.

Tesla will very, very likely be showcasing both the acceleration rate and potentially even a top speed demo at the event in Waco. Both of these demonstrations, performed with a vehicle that has such incredibly fast metrics, could easily be impacted by wind as well.

Tesla Roadster event requires restricted airspace, and the FAA obliges

Top Speed Demo

At high speeds, aerodynamic forces are already overwhelmingly present. A crosswind or sudden gust adds a layer of sideways force that the tires must counter with slip angle. On a short demo course, that force can shove the car off the intended line, especially in a light car with a low frontal area and little mass to resist the push.

Electric cars, due to their battery packs, have an advantage of an extremely low center of gravity, giving them extra stability. However, the speeds at which the Roadster could travel at the demo could spell some issues if crosswinds are present.

Gusts are worse than a steady wind because the load changes faster than a driver can smoothly correct. That shows up as weaving or a late correction. Headwinds and tailwinds can also spell disaster. Headwinds cut a measured top speed but raise the power needed to get there or maintain it. Meanwhile, a tailwind can inflate the top speed, and downforce issues could become more noticeable.

Wind also loads the body unevenly. A low car can feel light on the upwind side or see a sudden change in downforce if the gust hits a wing or diffuser at an angle. Tire temperature and pressure might stay near a normal level, but lateral grip can be lost as the vehicle is spent fighting the wind.

Acceleration Demo

Launch and 0-60 MPH runs are shorter, so the car spends less time exposed to forces that could cause things to go awry. However, the first second is very sensitive, as a crosswind at launch could yaw the car before speed builds and prior to aerodynamic impact being too great. The driver will be required to correct traction control or manage how much the wheels are spinning, which will likely be corrected automatically by some sort of traction control system within the Roadster (we are fairly certain Tesla will implement something brilliant with it).

These things could cause an unstable run.

A headwind would increase drag as speed rises, while a tailwind would do the opposite. Meanwhile, surface effects, like wind-driven dust, light debris, or even rain, could reduce grip at the exact moment the tires are asked for peak longitudinal force. Standing water plus a crosswind is a common reason an acceleration attempt might be scrapped.

Flying or Not

No matter what Tesla has in store for the Roadster, waiting for ideal conditions is a great idea. People who follow and support the company, along with the engineers involved in the Roadster program, have been waiting nine years since the last unveiling for this moment. Everything should be ideal.

Some speculate that it’s just not ready, and that’s ridiculous. Why would Tesla even schedule the event — albeit prematurely — after nine years if it was not ready? Why would they jump the gun now?

We were all excited for today, but it truly is the most ideal thing in the world to wait two more weeks so everything, including the weather, can be perfect. The delay is simply worth it. But Tesla, seriously, make this the last one.

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