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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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Elon Musk
Trump’s invite for Elon just reshuffled Tesla’s big Signature Delivery Event
Tesla rescheduled its final Model S farewell to May 20 after Musk joined Trump in China.
Tesla has rescheduled its Model S and Model X Signature Edition delivery event to Wednesday, May 20, 2026, after abruptly calling off the original May 12 celebration. The event will take place at Tesla’s factory at 45500 Fremont Boulevard in Fremont, California, the same location where the Model S first rolled off the line in 2012. Invitees received a follow-up email asking them to reconfirm attendance and download a new QR code ticket, with Tesla noting that all travel and accommodation expenses remain the buyer’s responsibility.
The reason behind the original cancellation came into focus the same day it was announced. President Trump invited Elon Musk, Apple’s Tim Cook, BlackRock’s Larry Fink, Boeing’s Kelly Ortberg, and executives from Goldman Sachs, Blackstone, Citigroup, and Meta to join his trip to China this week for a summit with President Xi Jinping. The agenda covers trade, artificial intelligence, export controls, Taiwan, and the Iran war, following weeks of escalating friction between Washington and Beijing over AI technology, sanctions, and rare earth exports. Trump wrote on Truth Social, “I am very much looking forward to my trip to China, an amazing Country, with a Leader, President Xi, respected by all.”
Tesla launches 200mph Model S “Gold” Signature in invite-only purchase
The vehicles at the center of all this are the last Model S and Model X units Tesla will ever build. Priced at $159,420 each, the 250 Model S and 100 Model X Signature Edition units come finished in Garnet Red with a one-year no-resale agreement, giving Tesla right of first refusal if the owner decides to sell. As Teslarati reported, the Model S defined Tesla’s early identity as a serious luxury automaker, and the Fremont factory line that built it is now being converted to manufacture Optimus humanoid robots.
Musk’s inclusion in the China delegation drew attention given his very public relationship with Trump, and the invitation signals the two have moved past and past grievances. Trump originally brought Musk on to lead the Department of Government Efficiency following his inauguration, and despite a sharp public dispute in mid-2025, the two have appeared together repeatedly in recent months. A seat on the China trip, the most diplomatically consequential visit of Trump’s current term, puts Musk back at the table on U.S. economic policy at a moment when Tesla’s China revenue remains one of the company’s most important financial pillars.
Tesla has launched a new solution to a rare but relevant Supercharger problem with a new Virtual Waitlist, a remedy that will solve sequencing confusion when there is a line to charge at one of the company’s locations.
Teslarati reported on what we called the Virtual Queue last month. In rare occurrences, there were physical altercations at Superchargers when someone might have cut in line to charge. Tesla started to develop some sort of system that would resolve this issue, and now it is finally rolling it out.
Tesla launches solution to end Supercharger fights once and for all
It will start with a Pilot Program, and Tesla is calling it the ‘Waitlist.’
Announced on May 11 on the official TeslaCharging X account, the pilot program is currently active at sites in Los Gatos, Mountain View, and San Francisco in California, as well as San Jose, CA, and the Bronx, NY (East Gun Hill Road). Drivers are encouraged to share feedback directly through the Tesla app to refine the system before a potential broader rollout.
We’re now testing a new waitlist feature at 5 Supercharger sites. Share feedback through the Tesla app to help us make it better.
– Los Gatos, CA – Los Gatos Boulevard
– Mountain View, CA – El Monte Avenue
– San Francisco, CA – Lombard Street
– San Jose, CA – Saratoga Avenue
-… pic.twitter.com/epTVzpJxgW— Tesla Charging (@TeslaCharging) May 11, 2026
Tesla released the video above to showcase the feature, which automatically joins the waitlist when your vehicle has the Supercharger with the wait as the destination in the navigation. There is also a notification that lets you know your place in line.
In this specific example, the video shows that the wait is less than five minutes, and that there are two cars ahead of the one in the video:
Credit: Tesla
Having a wait at a Supercharger is relatively rare, but it does happen. It is even more frequent now that there are more EVs allowed to use the Supercharger Network. Those non-Tesla EVs can also join the queue, as Tesla added in its social media release of the pilot program that they can join the waitlist using the Tesla app.
The release of this program should help alleviate the rare risk of incidents at Superchargers. Tesla will expand this program as it sees fit, and it gathers valuable data and reviews from users.
Investor's Corner
Tesla Optimus is already benefiting investors, top Wall Street firm says
Piper Sandler has updated its detailed valuation model for Tesla (NASDAQ: TSLA), concluding that at recent share prices around $400–$420, investors are essentially acquiring the company’s ambitious Optimus humanoid robot project at no extra cost.
Tesla Optimus is already benefiting investors from a fiscal standpoint, at least that is what Alexander Potter at Piper Sandler, a top Wall Street firm covering the company, says.
Piper Sandler has updated its detailed valuation model for Tesla (NASDAQ: TSLA), concluding that at recent share prices around $400–$420, investors are essentially acquiring the company’s ambitious Optimus humanoid robot project at no extra cost.
Analyst Alexander Potter, in the firm’s latest “Definitive Guide to Investing in Tesla,” built a comprehensive framework covering 17 separate product lines.
This granular approach values Tesla’s core businesses—including electric vehicles, energy storage, Full Self-Driving (FSD) software, in-house insurance, Supercharging network, and a standalone robotaxi operation—at approximately $400 per share, without assigning any value to Optimus or related inference-as-a-service opportunities.
“At $400/share, we think investors can buy Optimus for ‘free,’” Potter stated in the note. Piper Sandler maintained its Overweight rating on Tesla shares and a $500 price target, which implicitly attributes roughly $100 per share to the robot-related businesses— a figure the analyst views as potentially conservative.
The updated model incorporates elements often overlooked by other sell-side analysts, such as detailed forecasts for Tesla’s insurance operations, Supercharger revenue, and a distinct valuation for the robotaxi business separate from FSD software licensing. It also accounts for Tesla’s 2025 CEO compensation plan for the first time.
Potter acknowledged that his estimates for 2026 and 2027 fall below Wall Street consensus, citing factors like declining deliveries from certain discontinued models and reduced regulatory credit income.
However, he expressed limited concern, noting that traditional vehicle delivery metrics are expected to matter less over time as FSD subscriber growth and robotaxi deployment metrics gain prominence. On Optimus specifically, Potter suggested the humanoid robot program, combined with inference services, “arguably will be worth more than Tesla’s other businesses combined,” though the firm has not yet produced formal long-term forecasts for these segments.
Tesla shares have traded near the $400 range in recent sessions, reflecting ongoing investor focus on the company’s autonomous driving progress and expansion into robotics and AI. The Optimus project remains in early development stages, with Tesla aiming to deploy the robots initially for internal factory tasks before broader commercial applications.
This Piper Sandler analysis highlights the growing emphasis among some investors and analysts on Tesla’s long-term technology platform potential beyond its current automotive and energy businesses.
As with any forward-looking valuation, outcomes will depend on execution timelines, technological breakthroughs, regulatory approvals for autonomous systems, and market adoption of humanoid robotics—areas that carry significant uncertainty and execution risk.
The note underscores a common theme in Tesla coverage: differing views on how to quantify emerging high-growth opportunities like robotics within the company’s overall enterprise value. Investors are advised to consider their own risk tolerance and conduct thorough due diligence regarding these speculative elements.
Trump’s invite for Elon just reshuffled Tesla’s big Signature Delivery Event
Tesla launches its solution to rare but relevant Supercharger problem
