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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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Lucid unveils Lunar Robotaxi in bid to challenge Tesla’s Cybercab in the autonomous ride hailing race
Lucid’s Lunar robotaxi is gunning for Tesla’s Cybercab in the autonomous ride hailing race
![Lucid Lunar robotaxi concept [Credit: Rendering by TESLARATI]](https://www.teslarati.com/wp-content/uploads/2026/03/lucid-lunar-robotaxi-concept-teslarati-rendering.jpg)
Lucid Group pulled back the curtain on its purpose-built autonomous robotaxi platform dubbed the Lunar Concept. Announced at its New York investor day event, Lunar is arguably the company’s most ambitious concept yet, and a direct line of sight toward the autonomous ride haling market that Tesla looks to control.
At Lucid Investor Day 2026, the company introduced Lunar, a purpose-built robotaxi concept based on the Midsize platform.
A comparison to Tesla’s Cybercab is unavoidable. The concept of a Tesla robotaxi was first introduced by Elon Musk back in April 2019 during an event dubbed “Autonomy Day,” where he envisioned a network of self-driving Tesla vehicles transporting passengers while not in use by their owners. That vision took another major step in October 2024 when, Musk unveiled the Cybercab at the Tesla “We, Robot” event held at Warner Bros. Studios in Burbank, California, where 20 concept Cybercabs autonomously drove around the studio lot giving rides to attendees.
Fast forward to today, and Tesla’s ambitions are finally materializing, but not without friction. As we recently reported, the Cybercab is being spotted with increasing frequency on public roads and across the grounds of Gigafactory Texas, suggesting that the company’s road testing and validation program is ramping meaningfully ahead of mass production. Tesla already operates a small scale robotaxi service in Austin using supervised Model Ys, but the Cybercab is designed from the ground up for high-volume, low-cost production, with Musk stating an eventual goal of producing one vehicle every 10 seconds.
At Lucid Investor Day 2026, the company introduced Lunar, a purpose-built robotaxi concept based on the Midsize platform.
Into this landscape steps Lucid’s Lunar. Built on the company’s all-new Midsize EV platform, which will also underpin consumer SUVs starting below $50,000. The Lunar mirrors the Cybercab’s core philosophy of having two seats, no driver controls, and a focus on fleet economics. The platform introduces Lucid’s redesigned Atlas electric drive unit, engineered to be smaller, lighter, and cheaper to manufacture at scale.
Unlike Tesla’s strategy of building its own ride hailing network from scratch, Lucid is partnering with Uber. The companies are said to be in advanced discussions to deploy Midsize platform vehicles at large scale, with Uber CEO Dara Khosrowshahi publicly backing Lucid’s engineering credentials and autonomous-ready architecture.
In the investor day event, Lucid also outlined a recurring software revenue model, with an in-vehicle AI assistant and monthly autonomous driving subscriptions priced between $69 and $199. This can be seen as a nod to the software revenue stream that Tesla has long championed with its Full Self-Driving subscription.
Tesla’s Cybercab is targeting a price point below $30k and with operating costs as low as 20 cents per mile. But with regulatory hurdles still ahead, the window for competition is open. Lucid’s Lunar may not have a launch date yet, but it arrives at a pivotal moment, and when the robotaxi race is no longer viewed as hypothetical. Rather, every serious EV player needs to come to bat on the same plate that Tesla has had countless practice swings on over the last seven years.
Elon Musk
Brazil Supreme Court orders Elon Musk and X investigation closed
The decision was issued by Supreme Court Justice Alexandre de Moraes following a recommendation from Brazil’s Prosecutor-General Paulo Gonet.
Brazil’s Supreme Federal Court has ordered the closure of an investigation involving Elon Musk and social media platform X. The inquiry had been pending for about two years and examined whether the platform was used to coordinate attacks against members of the judiciary.
The decision was issued by Supreme Court Justice Alexandre de Moraes following a recommendation from Brazil’s Prosecutor-General Paulo Gonet.
According to a report from Agencia Brasil, the investigation conducted by the Federal Police did not find evidence that X deliberately attempted to attack the judiciary or circumvent court orders.
Prosecutor-General Paulo Gonet concluded that the irregularities identified during the probe did not indicate fraudulent intent.
Justice Moraes accepted the prosecutor’s recommendation and ruled that the investigation should be closed. Under the ruling, the case will remain closed unless new evidence emerges.
The inquiry stemmed from concerns that content on X may have enabled online attacks against Supreme Court justices or violated rulings requiring the suspension of certain accounts under investigation.
Justice Moraes had previously taken several enforcement actions related to the platform during the broader dispute involving social media regulation in Brazil.
These included ordering a nationwide block of the platform, freezing Starlink accounts, and imposing fines on X totaling about $5.2 million. Authorities also froze financial assets linked to X and SpaceX through Starlink to collect unpaid penalties and seized roughly $3.3 million from the companies’ accounts.
Moraes also imposed daily fines of up to R$5 million, about $920,000, for alleged evasion of the X ban and established penalties of R$50,000 per day for VPN users who attempted to bypass the restriction.
Brazil remains an important market for X, with roughly 17 million users, making it one of the platform’s larger user bases globally.
The country is also a major market for Starlink, SpaceX’s satellite internet service, which has surpassed one million subscribers in Brazil.
Elon Musk
FCC chair criticizes Amazon over opposition to SpaceX satellite plan
Carr made the remarks in a post on social media platform X.
U.S. Federal Communications Commission (FCC) Chairman Brendan Carr criticized Amazon after the company opposed SpaceX’s proposal to launch a large satellite constellation that could function as an orbital data center network.
Carr made the remarks in a post on social media platform X.
Amazon recently urged the FCC to reject SpaceX’s application to deploy a constellation of up to 1 million low Earth orbit satellites that could serve as artificial intelligence data centers in space.
The company described the proposal as a “lofty ambition rather than a real plan,” arguing that SpaceX had not provided sufficient details about how the system would operate.
Carr responded by pointing to Amazon’s own satellite deployment progress.
“Amazon should focus on the fact that it will fall roughly 1,000 satellites short of meeting its upcoming deployment milestone, rather than spending their time and resources filing petitions against companies that are putting thousands of satellites in orbit,” Carr wrote on X.
Amazon has declined to comment on the statement.
Amazon has been working to deploy its Project Kuiper satellite network, which is intended to compete with SpaceX’s Starlink service. The company has invested more than $10 billion in the program and has launched more than 200 satellites since April of last year.
Amazon has also asked the FCC for a 24-month extension, until July 2028, to meet a requirement to deploy roughly 1,600 satellites by July 2026, as noted in a CNBC report.
SpaceX’s Starlink network currently has nearly 10,000 satellites in orbit and serves roughly 10 million customers. The FCC has also authorized SpaceX to deploy 7,500 additional satellites as the company continues expanding its global satellite internet network.
![Lucid Lunar robotaxi concept [Credit: Rendering by TESLARATI]](https://www.teslarati.com/wp-content/uploads/2026/03/lucid-lunar-robotaxi-concept-teslarati-rendering-80x80.jpg)
Lucid unveils Lunar Robotaxi in bid to challenge Tesla’s Cybercab in the autonomous ride hailing race
Brazil Supreme Court orders Elon Musk and X investigation closed
