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SpaceX Starship prototype bears down on first Raptor engine tests
SpaceX’s fifth full-scale Starship prototype is fast approaching its first Raptor static fire tests after the company recently delivered one of the newest engines to the launch site.
Known as Starship SN5, the ship is the fifth SpaceX has built since full-scale prototype development began in early 2019, as well as the fourth full-scale ship the company has completed since it began producing upgraded hardware in January 2020. SN5 rolled from SpaceX’s Boca Chica, Texas rocket factory to nearby test and launch facilities on June 24th, less than a month after Starship SN4 was destroyed by operator error minutes after completing its fourth Raptor static fire in four weeks.
While Starship SN5 was already more or less complete, SN4’s explosive demise damaged the launch mount (used to secure and fuel prototypes) beyond repair, forcing SpaceX to rapidly build and outfit a replacement. SpaceX finished that replacement mount around June 20th, installed SN5 on it a few days later, and then spent about a week finalizing and inspecting both components.
After barely a month of downtime, Starship SN5 kicked off its first gauntlet of tests late on June 30th, carrying on into the early morning of July 1st. As usual, SpaceX began with an ambient-temperature pressure test, filling Starship’s tanks with neutral nitrogen gas to check for leaks. This time around, SN5 must have been put together with exceptional care, as the company was able to immediately proceed into the ship’s first cryogenic proof test just a few hours later.
CEO Elon Musk has yet to offer any confirmation but the implication is that SN5 performed beautifully during its first liquid nitrogen proof test. Notably, based on NASASpaceflight.com’s excellent unofficial coverage, SN5’s cryo proof was uniquely ambitious. It’s unclear what if the test infrastructure, SN5, general confidence in the vehicle, or some combination of the above components were upgraded, but SpaceX appeared to load Starship SN5 with liquid nitrogen incredibly quickly, taking just 20-30 minutes to fully fuel the rocket. Given that all of that liquid nitrogen (some 1000+ metric tons or ~3.2 million gallons) is being loaded through a single “quick disconnect” panel, it’s no mean feat and far outweighs SpaceX’s already speedy Falcon 9 and Heavy propellant loading.
SpaceX is famously the only current launch vehicle operator known to “sub-cool” its rockets’ propellant, effectively squeezing a performance boost of 5-10% out of the same rocket hardware by making said propellant colder – and thus denser. That performance increase comes with tradeoffs, though, adding significantly tighter operational constraints, lowering delay tolerances, and necessitating an extremely quick propellant load. Sub-cooled liquid oxygen and methane has always been part of SpaceX’s plans for Starship, so fast-load tests were inevitable, but it’s a great sign that the company is starting to seriously think about capabilities that will be necessary for efficient orbital launches.
Meanwhile, labeled “27”, the engine – logically assumed to be Raptor SN27 – SpaceX has just installed on Starship SN5 is also of interest. On top of Musk’s recent confirmation that SpaceX is already building Raptor SN30 (probably SN31 or SN32, now), SN27’s assignment to Starship SN5 confirms that the company has managed to complete (and test) at least one next-generation engines every other week since the first full-scale engine shipped to McGregor, Texas in February 2019.
For a brand new engine as complex as Raptor, that’s an impressive production milestone. Per Musk, the end-goal is to produce at least one Raptor per day in the near term – a necessity given that each Starship and Super Heavy booster pair will require at least 37 engines. To feasibly build a fleet of tens – let alone hundreds or thousands – of Starships and boosters, one engine per day is arguably the bare minimum required just for early orbital launch attempts and initial operations.
According to published schedules, Starship SN5’s first live wet dress rehearsal (WDR) and static fire tests could happen as early July 8th, with backups on the 9th and 10th. Coincidentally, SpaceX’s next orbital Falcon 9 launch is also expected on the 8th, meaning that both Starship and Falcon 9 could fire up more or less simultaneously.
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Tesla (NASDAQ: TSLA) is set to hold its Earnings Call for the first quarter of 2026 on Wednesday, and there are a lot of interesting things that are swirling around in terms of speculation from investors.
With the company’s executives, including CEO Elon Musk, answering a handful of questions that investors submit through the Say platform, fans want to know a lot of things about a lot of things.
These five questions come from Retail Investors, who are normal, everyday shareholders:
- When will we have the Optimus v3 reveal? When will Optimus production start, since we ended the Model S and Model X production earlier than mid-year? What’s the expected Optimus production rate exiting this year? What are the initial targeted skills?
- What milestones are you targeting for unsupervised FSD and Robotaxi expansion beyond Austin this year, and how will that drive recurring revenue?
- How will Hardware 3 cars reach Unsupervised Full Self-Driving?
- When do you expect Unsupervised Full Self-Driving to reach customer cars?
- When will Robotaxi expand past its current limited rollout?
Additionally, these are currently the three questions that are slated to be answered by Institutional Firms, which also answer a handful of questions during the call:
- Now that FSD has been approved in the Netherlands and is expected to launch across Europe this summer, can you discuss your Robotaxi strategy for the region?
- What enabled you to finish the AI5 tapeout early and were there any changes to the original vision? Last week, Elon said AI5 will go into Optimus and the Supercomputer, but one month ago said it would go into the Robotaxi. Has AI5 been dropped from the vehicle roadmap?
- Given the recent NHTSA incident filings, can you update us on the Robotaxi safety data? If safety validation remains the primary bottleneck, why not deploy thousands of vehicles to accelerate the removal of the safety driver?
The questions range through every current Tesla project, including FSD expansion and Optimus. However, many of the answers we will get will likely be repetitive answers we’ve heard in the past.
This is especially pertinent when the questions about when Unsupervised FSD will reach customer cars: we know Musk will say that it will happen this year. Is Tesla capable of that? Maybe. But a more transparent answer that is more revealing of a true timeline would be appreciated.
Hardware 3 owners are anxiously awaiting the arrival of FSD v14 Lite, which was promised to them last year for a release sometime this year.
The Earnings Call is set to take place on Wednesday at market close.
Elon Musk
Elon Musk reveals shocking Tesla Optimus patent detail
What looked promising on paper and in simulations failed to deliver the reliability required for a robot expected to handle delicate tasks like folding laundry, assembling electronics, or assisting in factories and homes.
Elon Musk revealed a shocking detail on the Tesla Optimus patent that was revealed last week. Despite it being made public for the first time, Musk said the company has already moved on from the design, an incredible truth about the development of new technology: things move fast.
Musk dropped a bombshell about the Tesla Optimus humanoid robot hand patent that was released last week. Musk, candidly replying to a post late at night on X, revealed that what is a new technology to many fans and insiders is actually old news to those developing the tech directly.
“We already changed the design,” Musk said. “This one didn’t actually work.”
We already changed the design. This one didn’t actually work.
— Elon Musk (@elonmusk) April 19, 2026
Patents, after all, are often viewed as blueprints for future products. Yet Musk revealed that the rolling contact mechanism—intended to provide smooth, low-friction articulation in the fingers—had already been scrapped after real-world testing exposed its shortcomings.
What looked promising on paper and in simulations failed to deliver the reliability required for a robot expected to handle delicate tasks like folding laundry, assembling electronics, or assisting in factories and homes.
The hand has been one of the biggest challenges for Tesla engineers since Optimus development started years ago. Musk has said that there is not enough recognition for how incredible and useful the human hand is, and designing one for a humanoid robot has been the biggest challenge of all.
Tesla is stumped on how to engineer this Optimus part, but they’re close
This moment underscores the persistent engineering hurdles in achieving reliable humanoid hand dexterity. Human fingers are marvels of evolution: 27 bones, intricate tendons, ligaments, and a network of sensors working in perfect harmony. Replicating that in metal and silicon is extraordinarily difficult.
Rolling contacts promised reduced wear and precise motion, but testing likely revealed issues with durability under repeated stress, grip stability on varied surfaces, or the micro-precision needed for fine motor skills.
These aren’t minor tweaks, but instead they represent fundamental challenges that have plagued robotics teams for decades. Even advanced competitors struggle here—hands remain the Achilles’ heel of most humanoids because the margin for error is razor-thin.
A fraction of a millimeter off, and a robot drops a glass or fails to button a shirt.
What makes Musk’s reply remarkable is how it signals Tesla’s direct communication style on prototype limitations. While many companies guard failures behind glossy marketing and vague timelines, Tesla openly shares setbacks.
Musk was forthcoming about the failure of this recent design. This transparency builds trust with investors, engineers, and fans. It shows Tesla treats Optimus development like true science: rapid iteration, rigorous testing, and zero tolerance for hype that doesn’t match reality.
The disclosure from Musk also highlights Tesla’s blistering pace of development. By the time the patents are published, which is often over a year after the initial filing, the technology has already evolved.
Optimus is far from a static product, and it’s a living project advancing weekly.
In the high-stakes race for general-purpose robots, Tesla’s approach stands out. Admitting a finger-joint design “didn’t actually work” isn’t a weakness—it’s confidence.
True innovation demands confronting failure head-on, and Musk just reminded the world that Optimus is being engineered that way. The next version of those hands is already in testing, and it will be better because Tesla isn’t afraid to say what didn’t work.
Elon Musk
Tesla is sending its humanoid Optimus robot to the Boston Marathon
Tesla’s Optimus robot is heading to the Boston Marathon finish line
Tesla’s Optimus humanoid robot will be stationed at the Tesla showroom at 888 Boylston Street in Boston, right along the final stretch of the Boston Marathon today, ready to cheer on runners and pose for photos with spectators.
According to a Tesla email shared by content creator Sawyer Merritt on X, Optimus will be at the Boston Boylston Street showroom on April 20, coinciding with Marathon Monday weekend. The Boston Marathon finishes on Boylston Street, and the surrounding area draws hundreds of thousands of spectators along with international broadcast coverage. Placing Optimus there puts it in front of a massive public audience at zero advertising cost.
Just got this email. @Tesla’s Optimus robot is coming to Boston.
“Join us from April 19 to 20, 2026, at Tesla Boston Boylston Street showroom to meet Optimus, our humanoid robot, for Marathon Monday. Optimus will be cheering with you on the sidelines and posing for photos.” pic.twitter.com/chxoooO2xV
— Sawyer Merritt (@SawyerMerritt) April 18, 2026
The Tesla showroom is at 888 Boylston Street, between Gloucester Street and Fairfield Street. The final mile of the marathon runs directly along Boylston Street, with runners passing the big stores before reaching the finish line at Copley Square.
Optimus was first announced at Tesla’s AI Day event on August 19, 2021, when Elon Musk presented a vision for a general-purpose robot designed to take on dangerous, repetitive, and unwanted tasks. In March 2026, Optimus appeared at the Appliance and Electronics World Expo in Shanghai, where on-site staff stated that mass production of the robot could begin by the end of 2026. Before that, it showed up at the Tesla Hollywood Diner opening in July 2025 and at a Miami showroom event in December 2025.
Tesla’s well-calculated display of Optimus gives the public a low-pressure first encounter with a robot that Tesla is preparing to soon deploy at scale. The company has previously indicated plans to manufacture Optimus robots at its Fremont facility at up to 1 million units annually, with an Optimus production line at Gigafactory Texas targeting 10 million units per year.
Tesla showcases Optimus humanoid robot at AWE 2026 in Shanghai
Musk has said that Optimus “has the potential to be more significant than the vehicle business over time,” and separately that roughly 80 percent of Tesla’s future value will come from the robot program. Whether that holds depends on production execution. For now, Boston gets a preview of what that future looks like, standing at the finish line on Boylston Street while 32,000 runners pass by.
Tesla Q1 Earnings: What Elon Musk and Co. will answer during the call
Elon Musk reveals shocking Tesla Optimus patent detail
