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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 FSD’s newest model is coming, and it sounds like ‘the last big piece of the puzzle’
“There’s a model that’s an order of magnitude larger that will be deployed in January or February 2026.”
Tesla Full Self-Driving’s newest model is coming very soon, and from what it sounds like, it could be “the last big piece of the puzzle,” as CEO Elon Musk said in late November.
During the xAI Hackathon on Tuesday, Musk was available for a Q&A session, where he revealed some details about Robotaxi and Tesla’s plans for removing Robotaxi Safety Monitors, and some information on a future FSD model.
While he said Full Self-Driving’s unsupervised capability is “pretty much solved,” and confirmed it will remove Safety Monitors in the next three weeks, questions about the company’s ability to give this FSD version to current owners came to mind.
Musk said a new FSD model is coming in about a month or two that will be an order-of-magnitude larger and will include more reasoning and reinforcement learning.
He said:
“There’s a model that’s an order of magnitude larger that will be deployed in January or February 2026. We’re gonna add a lot of reasoning and RL (reinforcement learning). To get to serious scale, Tesla will probably need to build a giant chip fab. To have a few hundred gigawatts of AI chips per year, I don’t see that capability coming online fast enough, so we will probably have to build a fab.”
NEWS: Elon Musk says FSD Unsupervised is “pretty much solved at this point” and that @Tesla will be launching Robotaxis with no safety monitors in about 3 weeks in Austin, Texas. He also teased a new FSD model is coming in about 1-2 months.
“We’re just going through validation… https://t.co/Msne72cgMB pic.twitter.com/i3wfKX3Z0r
— Sawyer Merritt (@SawyerMerritt) December 10, 2025
It rings back to late November when Musk said that v14.3 “is where the last big piece of the puzzle finally lands.”
With the advancements made through Full Self-Driving v14 and v14.2, there seems to be a greater confidence in solving self-driving completely. Musk has also personally said that driver monitoring has been more relaxed, and looking at your phone won’t prompt as many alerts in the latest v14.2.1.
This is another indication that Tesla is getting closer to allowing people to take their eyes off the road completely.
Along with the Robotaxi program’s success, there is evidence that Tesla could be close to solving FSD. However, it is not perfect. We’ve had our own complaints with FSD, and although we feel it is the best ADAS on the market, it is not, in its current form, able to perform everything needed on roads.
But it is close.
That’s why there is some legitimate belief that Tesla could be releasing a version capable of no supervision in the coming months.
All we can say is, we’ll see.
Investor's Corner
SpaceX IPO is coming, CEO Elon Musk confirms
However, it appears Musk is ready for SpaceX to go public, as Ars Technica Senior Space Editor Eric Berger wrote an op-ed that indicated he thought SpaceX would go public soon. Musk replied, basically confirming it.
Elon Musk confirmed through a post on X that a SpaceX initial public offering (IPO) is on the way after hinting at it several times earlier this year.
It also comes one day after Bloomberg reported that SpaceX was aiming for a valuation of $1.5 trillion, adding that it wanted to raise $30 billion.
Musk has been transparent for most of the year that he wanted to try to figure out a way to get Tesla shareholders to invest in SpaceX, giving them access to the stock.
He has also recognized the issues of having a public stock, like litigation exposure, quarterly reporting pressures, and other inconveniences.
However, it appears Musk is ready for SpaceX to go public, as Ars Technica Senior Space Editor Eric Berger wrote an op-ed that indicated he thought SpaceX would go public soon.
Musk replied, basically confirming it:
As usual, Eric is accurate
— Elon Musk (@elonmusk) December 10, 2025
Berger believes the IPO would help support the need for $30 billion or more in capital needed to fund AI integration projects, such as space-based data centers and lunar satellite factories. Musk confirmed recently that SpaceX “will be doing” data centers in orbit.
AI appears to be a “key part” of SpaceX getting to Musk, Berger also wrote. When writing about whether or not Optimus is a viable project and product for the company, he says that none of that matters. Musk thinks it is, and that’s all that matters.
It seems like Musk has certainly mulled something this big for a very long time, and the idea of taking SpaceX public is not just likely; it is necessary for the company to get to Mars.
The details of when SpaceX will finally hit that public status are not known. Many of the reports that came out over the past few days indicate it would happen in 2026, so sooner rather than later.
But there are a lot of things on Musk’s plate early next year, especially with Cybercab production, the potential launch of Unsupervised Full Self-Driving, and the Roadster unveiling, all planned for Q1.
Tesla has added the 15th automaker to the growing list of companies whose EVs can utilize the Supercharger Network this year, as BMW is the latest company to gain access to the largest charging infrastructure in the world.
BMW became the 15th company in 2025 to gain Tesla Supercharger access, after the company confirmed to its EV owners that they could use any of the more than 25,000 Supercharging stalls in North America.
Welcome @BMW owners.
Download the Tesla app to charge → https://t.co/vnu0NHA7Ab
— Tesla Charging (@TeslaCharging) December 10, 2025
Newer BMW all-electric cars, like the i4, i5, i7, and iX, are able to utilize Tesla’s V3 and V4 Superchargers. These are the exact model years, via the BMW Blog:
- i4: 2022-2026 model years
- i5: 2024-2025 model years
- 2026 i5 (eDrive40 and xDrive40) after software update in Spring 2026
- i7: 2023-2026 model years
- iX: 2022-2025 model years
- 2026 iX (all versions) after software update in Spring 2026
With the expansion of the companies that gained access in 2025 to the Tesla Supercharger Network, a vast majority of non-Tesla EVs are able to use the charging stalls to gain range in their cars.
So far in 2025, Tesla has enabled Supercharger access to:
- Audi
- BMW
- Genesis
- Honda
- Hyundai
- Jaguar Land Rover
- Kia
- Lucid
- Mercedes-Benz
- Nissan
- Polestar
- Subaru
- Toyota
- Volkswagen
- Volvo
Drivers with BMW EVs who wish to charge at Tesla Superchargers must use an NACS-to-CCS1 adapter. In Q2 2026, BMW plans to release its official adapter, but there are third-party options available in the meantime.
They will also have to use the Tesla App to enable Supercharging access to determine rates and availability. It is a relatively seamless process.
Tesla FSD’s newest model is coming, and it sounds like ‘the last big piece of the puzzle’
SpaceX IPO is coming, CEO Elon Musk confirms
