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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 just gave what is perhaps its biggest signal yet that the launch of the Cybercab, its autonomous ride-hailing-geared car, is imminent.
The Cybercab has been spotted outside of Gigafactory Texas in massive numbers over the past few days, with hundreds of units being stored on property just days after the vehicle received a Certificate of Conformity from the EPA.
Today, things were a bit different.
Cybercabs spotted on Giga Texas property today had an addition: a Cybercab decal on the side, reminiscent of the “Robotaxi” ones that were placed on Model Ys just as the company launched its ride-sharing platform about a year ago.
Giga Texas drone operator Joe Tegtmeyer noticed the change today:
Tesla Cybercabs are now getting “Cybercab” logos on the side of them!
Tesla did the same with Model Ys that were given “Robotaxi” logos: https://t.co/DanANtw1m7 pic.twitter.com/FqOhH0S9Ks
— TESLARATI (@Teslarati) June 19, 2026
Tesla could be signaling that the Cybercab is preparing to enter the Robotaxi fleet in the coming weeks or months with this move. It seems more symbolic than anything; Tesla is ready to throw Cybercabs in the ride-hailing platform just as it did with Model Ys last year.
The addition of the Certificate of Conformity awarded to the Cybercab is another major factor working to Tesla’s advantage. The company now has permission from the EPA to allow the vehicle to operate on public roads and enter the chain of commerce. It’s officially street legal.
Tesla Cybercab specs revealed: range, curb weight, range ratings, and more
The big question that remains is whether Tesla will be able to operate the car without a safety monitor, especially considering it plans to put the car out there without a steering wheel or pedals. With the Cybercab only having a seating capacity of two, it is hard to believe Tesla will even consider putting a Safety Monitor in the car.
It did recently self-certify as Level 4 and has the ability to operate driverless vehicles in the State of Texas under a law that took effect on May 28. You can read more about that here:
Tesla’s Robotaxi dreams just took a massive step toward reality
We’d imagine Cybercabs will be on the roads as soon as July, but August will likely be a better estimate of when the car will be entered into the Cybercab fleet. It all depends at where Tesla is, as they’ve truly prioritized safety with the rollout of the Robotaxi platform.
Elon Musk has publicly questioned Moody’s credit assessments following the rating agency’s decision to assign SpaceX a Baa1 investment-grade rating, two notches above Tesla’s Baa3. The comments came amid discussions comparing the two companies’ financial profiles.
SpaceX earned its first-time Baa1 rating with a stable outlook from Moody’s. The agency highlighted the company’s leadership in orbital launches, the growing recurring revenue from its Starlink satellite network, strong vertical integration, U.S. government contracts, and emerging opportunities in AI infrastructure.
These factors were cited as supporting robust cash flows, margin expansion, and financial flexibility.
Musk responded directly: “Tesla’s credit rating is ridiculously low tbh,” and added, “Yeah, makes no sense. Tesla has over $40B in cash, no debt, and is consistently profitable!” His remarks underscored Tesla’s balance sheet strength and profitability at a time when many traditional automakers continue to report losses in the shift to electric vehicles.
Yeah, makes no sense.
Tesla has over $40B in cash, no debt and is consistently profitable!
— Elon Musk (@elonmusk) June 19, 2026
Tesla maintains a leading position in the global EV market, with diversification into energy and storage, battery technology, and robotics through projects like Optimus. Recent financial updates show the company generated positive free cash flow of $1.4 billion in Q1 2026, supported by operating cash flow of $3.9 billion. Cash and short-term investments stood at approximately $44.7 billion.
Moody’s has affirmed Tesla’s Baa3 issuer rating with a stable outlook in periodic reviews, acknowledging the company’s EV leadership, technology strengths, including AI for autonomous vehicles, solid profitability, and strong liquidity.
Tesla (TSLA) scores Baa3 Moody’s rating for ‘stable’ outlook
However, the agency has also noted challenges in the automotive segment and expectations for margin pressures.
Musk’s critique highlights a common debate about how traditional rating methodologies apply to high-growth, capital-intensive technology companies. SpaceX benefits from long-term government-backed contracts and diversified, recurring revenue streams, while Tesla’s valuation reflects heavy investment in future technologies such as autonomy and robotics.
Both ratings remain investment-grade, yet the one-notch difference has fueled online discussion about potential inconsistencies in evaluating innovative firms.
The exchange comes as SpaceX explores financing options following its recent valuation milestones, while Tesla continues executing on its multi-year roadmap. Musk’s pointed response serves as a reminder that credit ratings, though influential for borrowing costs, represent one lens through which markets assess corporate strength—and that company leaders often view their financial positions through the lens of long-term innovation and cash generation rather than short-term risk metrics alone.
A new report from Reuters claims that a transport authority in Sweden is pushing back against the approval of Tesla’s Full Self-Driving suite because it will travel over speed limits.
The report says the Swedish Transport Administration (TRV) recommends the European Union votes against FSD’s approval. TRV believes it should not be approved until Tesla disables FSD’s ability to speed.
TRV sent a letter to the European Union’s Technical Committee on Motor Vehicles (TCMV), which is set to meet on June 30 to discuss the potential approval of the Tesla FSD suite in the country. Tesla, which has received various approvals in Europe over the past two months, has not provided a comment.
Teslas operating on FSD do travel over the speed limit, depending on the Speed Profile that is chosen. Drivers have the ability to disengage FSD at any point; Tesla specifically states that those supervising the suite are responsible for its actions.
Let’s cut to the chase: humans operating any vehicle speed almost daily in the United States. Realistically, speed limits in the U.S. are more frequently treated as speed minimums. However, other countries are different, and driving behaviors are less aggressive.
TRV believes that “allowing automated systems to systematically exceed legal speed limits…risks undermining both the legal framework and the expected safety benefits of vehicle automation,” the report stated. It’s surprising that Tesla has not received this claim from other countries previously.
This could be a good argument to bring Max Speed back, the setting that previously allowed the driver to choose the absolute fastest the car would travel.
This would still put the responsibility of supervision in the hands of the driver. It would allow the driver to choose whether the car would travel over the speed limit or not, acknowledging that they set the speed, and if they get pulled over, there would be no ability to argue it.
However, it does not seem as if this is something Tesla will do, especially considering many U.S. drivers have requested the feature in an effort to eliminate speeding or at least tone it down. The company has not shown any interest in bringing it back.
Tesla has approvals for FSD in Europe in Estonia, Lithuania, Denmark, the Netherlands, and Belgium.
Tesla Cybercab launch is imminent after latest sighting at Giga Texas
Elon Musk says this part of Tesla ‘makes no sense’
