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SpaceX’s Starship Raptor Vacuum engine plans laid out by CEO Elon Musk
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.
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.
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.
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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Tesla Cybercab rides are officially open to the public in Austin, Texas, as the company confirmed on Thursday following its launch event that the two-seater would be available in the company’s Robotaxi fleet.
Cybercab is Tesla’s first vehicle completely void of any manual controls. It has no steering wheel and no pedals, and it will utilize Tesla’s Full Self-Driving fleet to operate. The first rides have already happened, as those at the event were able to hail a Cybercab to any location within the company’s geofence in Austin.
Tesla’s $25K car is the Cybercab with no steering wheel or pedals
The addition of Cybercab to the public Robotaxi fleet is a major statement in Tesla’s trek to launch fully autonomous driving. For years, critics have complained about the need for drivers to continuously supervise the vehicle.
With Cybercab, there are no manual controls in the cockpit other than to control the seat, the center screen, and the climate. The vehicle is fully geared toward being a living room on wheels in a sense: equipped with Starlink V5 satellites, CEO Elon Musk said the vehicle would enable 4K live video, gaming, and other entertainment options during travel.
Cybercab is basically a super comfortable lounge on wheels with a great TV and epic sound https://t.co/X1aWKoJdJV
— Elon Musk (@elonmusk) September 3, 2026
Musk noted that Cybercab is “designed and built for maximally efficient autonomous operation.”
Tesla continues to push the envelope on autonomy, and over the next several months, the company could start selling Cybercab units to the public.
The company opened up a public interest form on its website to gauge demand, and many have already submitted requests to purchase a fleet of Cybercab units for their own personal ride-hailing side hustle.
The launch of Cybercab in this area marks a major accomplishment for Tesla, as it also announced that it has reached 1 million unsupervised autonomous miles since launching driverless rides on the Robotaxi fleet.
Things are moving along at a fine pace, and although we have waited for this for some time, the day has finally come when Tesla is offering self-driving rides of some kind to the public.
Tesla has quietly opened a public interest form for companies that want to buy fleets of its purpose-built Cybercab robotaxis, marking the first official channel for commercial purchases of the two-seat autonomous vehicle. The form went live on September 3, the same day Tesla hosted an invite-only Cybercab launch event in Austin, Texas.
Tesla titled the page “Help Us Build Our Robotaxi Network.” Applicants provide name, email, phone number, company name, and deployment region. They then select one or more categories: Cybercab fleet vehicle purchasing, mobility hubs and infrastructure, event collaboration, or other. Tesla says a representative will follow up with those who express commercial interest.
Tesla has introduced a new form that you can fill out if you are interested in purchasing a fleet of Cybercabs:
Form: https://t.co/Ut0yoiEyXD pic.twitter.com/uuaCXmksIO
— Sawyer Merritt (@SawyerMerritt) September 3, 2026
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Until now, the company had no public ordering path for the vehicle, which was first shown as a concept at the October 2024 “We, Robot” event.
The Cybercab is designed from the ground up for unsupervised operation. It has no steering wheel and no pedals.
Regulatory filings list a 48-kilowatt-hour battery, a single 219-horsepower front motor, a curb weight of 3,113 pounds, and an EPA-adjusted range near 290 to 300 miles. Tesla has already registered dozens of the vehicles with Texas authorities and has been testing them on public streets around Austin.
Tesla Cybercab sightings broaden well outside of Austin with autonomy in focus
The company’s existing Robotaxi service, which currently uses modified Model Y vehicles in parts of Texas and Florida, is expected to add Cybercabs as production ramps up at Gigafactory Texas.
The form signals that Tesla is preparing to treat the Cybercab as more than an in-house fleet asset. Investors and operators have discussed buying groups of the vehicles and placing them on Tesla’s ride-hailing network, with Tesla taking a platform fee. High-profile figures have publicly stated plans to acquire fleets if Tesla allows third-party ownership.
The new page gives those parties a direct way to register interest rather than waiting for a conventional configurator.
Whether the form leads quickly to firm purchase agreements remains unclear. Regulatory approval for widespread unsupervised operation still varies by state, and Tesla has not published pricing or delivery timelines for fleet customers. The company has previously discussed a target price near $25,000 to $30,000 per vehicle.
For now, the form is an early signal that Tesla wants partners to help scale the network rather than operate every Cybercab itself.
Pairing the launch of the Cybercab fleet form with the Austin event is no coincidence. Tesla is inviting businesses to participate in the next phase of its Robotaxi plan at the moment the production vehicle first appears in public.
Tesla has updated its Robotaxi app so riders can pick which vehicle they want before they book. The latest in-app screens now show two options side by side: the two-seat Cybercab and the four-seat Model Y.
A screenshot circulating Thursday shows the change in practice. In Austin, a rider could choose a gold Cybercab for two people or a Model Y for four. Tesla’s updated description calls Cybercab “our first purpose-built autonomous vehicle,” designed for safety, accessibility, and comfort, and says the lineup is available only through the Robotaxi app.
Tesla has updated their Robotaxi page in the App Store. You’ll be able to select if you want a Cybercab or Model Y Robotaxi.
“Our Robotaxi vehicle lineup now includes Cybercab, our first purpose-built autonomous vehicle. Designed for safety, accessibility and comfort, Cybercab… pic.twitter.com/Jff4klilDr
— Sawyer Merritt (@SawyerMerritt) September 3, 2026
The distinction is more than cosmetic, and it’s important to note that Robotaxi refers to the platform, while Cybercab refers to a vehicle.
Model Y Robotaxis have carried the service since it opened in Austin in mid-2025 and later expanded to Dallas, Houston, and parts of Florida. Those vehicles are converted production SUVs that still have steering wheels and pedals.
Cybercab is different. It has no driver controls, butterfly doors, a low seat height meant to work with wheelchairs, extra trunk space for assistive devices, and braille on the handles. Tesla has registered dozens of the two-seaters with Texas regulators in the days leading up to its September 3 Austin event.
Giving riders a choice lets Tesla match the vehicle to the trip. Most rides involve one or two people, which is where Cybercab is meant to be cheaper and more efficient to operate. Groups of three or four, or anyone who needs more space, can still request a Model Y.
The same app handles booking, payment, cabin settings, and, on Cybercab, features such as phone-based door opening and in-cabin voice controls.
The update does not mean every city suddenly has both cars available. Cybercab support is listed for Austin first, and the purpose-built fleet is still small compared with the existing Model Y roster. Even so, the app change marks a shift from a single-vehicle pilot to a mixed fleet.
Riders can now choose between the compact, purpose-built robotaxi and the familiar SUV that launched the service.
Tesla opens Cybercab rides to the public, with no steering wheel or pedals
Tesla hints its already prepping for Cybercab fleet orders
