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SpaceX Starship booster’s ‘hot gas’ thrusters make first public appearance
‘Hot gas’ thrusters meant to boost the efficiency of SpaceX’s Starship spacecraft and Super Heavy boosters have been spotted in public for the first time.
On the evening of June 21st, spaceflight photographer Brady Kenniston – on assignment for NASASpaceflight – caught the first glimpses ever of what amounts to the newest rocket engine designed and built by SpaceX. As yet unnamed, SpaceX CEO Elon Musk has consistently referred to the new engine as a “hot gas thruster” for several years, though virtually no concrete details have ever been shared.
The reason behind the lack of major visible progress is simple enough: until Starship is ready for serious orbital testing, hot-gas thrusters just aren’t necessary. Instead, SpaceX has relied on tried and true cold gas thrusters derived – or quite literally taken, in the case of Starhopper – from those used on Falcon 9 and Falcon Heavy boosters to maintain attitude control in space and safely land back on Earth.
For Starhopper and Starships SN5 and SN6, all three of which focused on simple hop tests, those cold-gas thrusters primarily augmented Raptor’s thrust vectoring capabilities by fine-tuning vehicle rotation and attitude. On Starships SN8, SN9, SN10, SN11, and SN15, cold-gas thrusters played a more substantial role in their more complex medium-altitude test flights, flipping each ship horizontal at apogee, helping to maintain stability during skydiver-style freefalls back to Earth, and augmenting three Raptor engines during the final landing flip and landing burn.
By all appearances, the thrusters did their jobs perfectly on all nine test flights. However, those eight suborbital prototypes could all afford to expend large portions of their mass budgets on a plethora of pressure vessels filled with tons of nitrogen gas. More importantly, empty Starships and their Super Heavy boosters are expected to weigh anywhere from 10-50 times more than Falcon 9’s booster and upper stage, and SpaceX’s suborbital prototypes have also required much less performance (delta V) than operational ships and boosters will need.
-->Cold gas (nitrogen) thrusters are too inefficient and the exponential aspects of rocket engineering too cruel for what works on Falcon to efficiently meet the needs of Starship and Super Heavy. SpaceX’s long-planned solution has been the development of a bipropellant thruster that would borrow from Raptor expertise and use the same methane and oxygen propellant – albeit in their high-pressure gaseous forms. If properly realized, such a thruster could offer around five times the efficiency and thrust of a similarly-sized cold-gas system – a boon for maneuvering and manipulating massive 100-250 ton (~250,000-550,000 lb) ships and boosters in space.
In theory, moving from nitrogen to methalox thrusters also means that Starship could refuel its thrusters using a tiny fraction of the vast supply of liquid methane and oxygen propellant it will already be carrying to the Moon or Mars. Ultimately, though, Musk says that those hot gas attitude control thrusters will debut on the Super Heavy booster assigned to Starship’s first orbital test flight. While SpaceX’s initial July target now appears to be out of the question, all flight and pad hardware could still be ready to launch as early as August or September.
Update: One month after Elon Musk stated that SpaceX was “aiming” to have hot gas thrusters on the first flightworthy Super Heavy booster, the CEO says those thrusters would be “an unnecessary complication for now” and “are being removed to speed up time to” Starship’s first orbital launch.
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Tesla scores major hire as Apple scientist moves to Optimus team
Chen, who advanced from individual contributor to technical lead during his time at Apple, noted that he was blown away by Tesla’s efforts and synergy.
Former Apple research scientist Yilun Chen has left the tech giant to join Tesla’s Optimus AI team. Chen, who advanced from individual contributor to technical lead during his time at Apple, noted that he was blown away by Tesla’s efforts and synergy.
Apple veteran closes a major chapter
In a farewell note, Yilun Chen reflected on his tenure at Apple as a period defined by rapid growth and exposure to notable internal projects, some of which remain unreleased. His roles spanned engineering, research, early product incubation, and hands-on prototyping, allowing him to build expertise across both mature and emerging teams.
Chen credited mentors, colleagues, and cross-functional collaborators for shaping his trajectory, calling the experience unforgettable and emphasizing how each team taught him different lessons about scaling technology, guiding product vision, and navigating fast-moving research environments. “Each role has offered me invaluable unique lessons… My deepest gratitude goes to my colleagues, mentors and friends,” he wrote.
Tesla’s Optimus lab secured the hire
Chen said the move to Tesla was driven by the momentum surrounding Optimus, a humanoid robot powered by LLM-driven reasoning and Physical AI. After visiting Tesla’s Optimus lab, he admitted that he was “totally blown away by the scale and sophistication of the Optimus lab and deep dedication of people when I got to visit the office.”
His first week at Tesla, he noted, involved spontaneous deep-tech discussions, a flat team structure, rapid prototyping cycles, and what he called a “crazy ideas with super-fast iterations” culture. Chen emphasized that the team’s ambition, as well as its belief that humanoid robots are now within reach, creates an energy level that feels aimed at changing the world.
-->“You can feel the energy to change the world here,” he wrote in a post on social media.
Elon Musk
Elon Musk gives nod to SpaceX’s massive, previously impossible feat
It was the booster’s 30th flight, a scenario that seemed impossible before SpaceX became a dominant force in spaceflight.
Elon Musk gave a nod to one of SpaceX’s most underrated feats today. Following the successful launch of the Transporter-15 mission, SpaceX seamlessly landed another Falcon 9 booster on a droneship in the middle of the ocean.
It was the booster’s 30th flight, a scenario that seemed impossible before SpaceX became a dominant force in spaceflight.
Elon Musk celebrates a veteran Falcon 9 booster’s feat
SpaceX completed another major milestone for its Smallsat Rideshare program on Friday, successfully launching and deploying 140 spacecraft aboard a Falcon 9 from Vandenberg Space Force Base. The mission, known as Transporter-15, lifted off two days later than planned after a scrub attributed to a ground systems issue, according to SpaceFlight Now. SpaceX confirmed that all payloads designed to separate from the rocket were deployed as planned.
The Falcon 9 used for this flight was booster B1071, one of SpaceX’s most heavily flown rockets. With its 30th mission completed, it becomes the second booster in SpaceX’s fleet to reach that milestone. B1071’s manifest includes five National Reconnaissance Office missions, NASA’s SWOT satellite, and several previous rideshare deployments, among others. Elon Musk celebrated the milestone on X, writing “30 flights of the same rocket!” in his post.
Skeptics once dismissed reusability as unfeasible
While rocket landings are routine for SpaceX today, that was not always the case. Industry veterans previously questioned whether reusable rockets could ever achieve meaningful cost savings or operational reliability, often citing the Space Shuttle’s partial reusability as evidence of failure.
-->In 2016, Orbital ATK’s Ben Goldberg argued during a panel that even if rockets could be reusable, they do not make a lot of sense. He took issue with Elon Musk’s claims at the time, Ars Technica reported, particularly when the SpaceX founder stated that fuel costs account for just a fraction of launch costs.
Goldberg noted that at most, studies showed only a 30% cost reduction for low-Earth orbit missions by using a reusable rocket. “You’re not going to get 100-fold. These numbers aren’t going to change by an order of magnitude. They’re just not. That’s the state of where we are today,” he said.
Former NASA official Dan Dumbacher, who oversaw the Space Launch System, expressed similar doubts in 2014, implying that if NASA couldn’t make full reusability viable, private firms like SpaceX faced steep odds.
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Tesla AI and Autopilot VP hints that Robovan will have RV conversions
Tesla’s vice president of AI and Autopilot software, Ashok Elluswamy, hinted at the linitiative in a reply to Y Combinator CEO Garry Tan.
It appears that Tesla is indeed considering an RV in its future pipeline, though the vehicle that would be converted for the purpose would be quite interesting. This is, at least, as per recent comments by a Tesla executive on social media platform X.
Robovan as an RV
Tesla’s vice president of AI and Autopilot software, Ashok Elluswamy, hinted at the linitiative in a reply to Y Combinator CEO Garry Tan, who called for a startup to build RVs with Full Self-Driving capabilities. In his reply, Elluswamy simply stated “On it,” while including a photo of Tesla’s autonomous 20-seat people mover.
Tesla unveiled the Robovan in October 2024 at the “We, Robot” event. The vehicle lacks a steering wheel and features a low floor for spacious interiors. The vehicle, while eclipsed by the Cybercab in news headlines, still captured the imagination of many, as hinted at by X users posting AI-generated images of Robovan RV conversions with beds, kitchens and panoramic windows on social media platforms. One such render by Tesla enthusiast Mark Anthony reached over 300,000 views on X.
Elon Musk on the Robovan
Elon Musk addressed the Robovan’s low profile in October 2024, stating the van uses automatic load-leveling suspension that raises or lowers based on road conditions. The system maintains the futuristic look while handling uneven pavement, Musk wrote on X. The CEO also stated that the Robovan is designed to be very airy inside, which would be great for an RV.
“The view from the inside is one of extreme openness, with visibility in all directions, although it may appear otherwise from the outside. The unusually low ground clearance is achieved by having an automatic load-leveling suspension that raises or lowers, based on smooth or bumpy road conditions,” Musk stated.
-->Elluswamy’s response on X suggests that Tesla is considering a Robovan RV conversion, though it would be interesting to see how the company will make the vehicle capable of reaching campsites. The Robovan has a very low ground clearance, after all, and campsites tend to be in unpaved areas.
Tesla scores major hire as Apple scientist moves to Optimus team
Elon Musk gives nod to SpaceX’s massive, previously impossible feat
