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SpaceX Starship booster’s ‘hot gas’ thrusters make first public appearance

While different in several key ways, new methane-oxygen thrusters recently spotted for the first time on Starship hardware are likely similar to Raptor and Crew Dragon's SuperDraco abort thrusters. (SpaceX)

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‘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.

https://www.youtube.com/watch?v=y23V1pYq0uw

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.

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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.

Eric Ralph is Teslarati's senior spaceflight reporter and has been covering the industry in some capacity for almost half a decade, largely spurred in 2016 by a trip to Mexico to watch Elon Musk reveal SpaceX's plans for Mars in person. Aside from spreading interest and excitement about spaceflight far and wide, his primary goal is to cover humanity's ongoing efforts to expand beyond Earth to the Moon, Mars, and elsewhere.

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Why Tesla Roadster unveiling delay might have nothing to do with it flying

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tesla roadster elon musk flying
Credit: Grok

Tesla announced on Monday that the Roadster event scheduled for today would be postponed due to the need for it to be held outside.

Less than 24 hours later, CEO Elon Musk broadened that by stating it was due to high winds, immediately sending everyone into a frenzy over the Roadster’s potential ability to fly.

And realistically, it could definitely have to do with it flying, hovering, or hopping; whatever Tesla has in mind for this demonstration could not be impacted by wind. However, it might have nothing to do with the vehicle flying whatsoever, and instead could be a simple precaution, as the Roadster is a very unique vehicle with some already official specs that are just mind-blowing.

Tesla will very, very likely be showcasing both the acceleration rate and potentially even a top speed demo at the event in Waco. Both of these demonstrations, performed with a vehicle that has such incredibly fast metrics, could easily be impacted by wind as well.

Tesla Roadster event requires restricted airspace, and the FAA obliges

Top Speed Demo

At high speeds, aerodynamic forces are already overwhelmingly present. A crosswind or sudden gust adds a layer of sideways force that the tires must counter with slip angle. On a short demo course, that force can shove the car off the intended line, especially in a light car with a low frontal area and little mass to resist the push.

Electric cars, due to their battery packs, have an advantage of an extremely low center of gravity, giving them extra stability. However, the speeds at which the Roadster could travel at the demo could spell some issues if crosswinds are present.

Gusts are worse than a steady wind because the load changes faster than a driver can smoothly correct. That shows up as weaving or a late correction. Headwinds and tailwinds can also spell disaster. Headwinds cut a measured top speed but raise the power needed to get there or maintain it. Meanwhile, a tailwind can inflate the top speed, and downforce issues could become more noticeable.

Wind also loads the body unevenly. A low car can feel light on the upwind side or see a sudden change in downforce if the gust hits a wing or diffuser at an angle. Tire temperature and pressure might stay near a normal level, but lateral grip can be lost as the vehicle is spent fighting the wind.

Acceleration Demo

Launch and 0-60 MPH runs are shorter, so the car spends less time exposed to forces that could cause things to go awry. However, the first second is very sensitive, as a crosswind at launch could yaw the car before speed builds and prior to aerodynamic impact being too great. The driver will be required to correct traction control or manage how much the wheels are spinning, which will likely be corrected automatically by some sort of traction control system within the Roadster (we are fairly certain Tesla will implement something brilliant with it).

These things could cause an unstable run.

A headwind would increase drag as speed rises, while a tailwind would do the opposite. Meanwhile, surface effects, like wind-driven dust, light debris, or even rain, could reduce grip at the exact moment the tires are asked for peak longitudinal force. Standing water plus a crosswind is a common reason an acceleration attempt might be scrapped.

Flying or Not

No matter what Tesla has in store for the Roadster, waiting for ideal conditions is a great idea. People who follow and support the company, along with the engineers involved in the Roadster program, have been waiting nine years since the last unveiling for this moment. Everything should be ideal.

Some speculate that it’s just not ready, and that’s ridiculous. Why would Tesla even schedule the event — albeit prematurely — after nine years if it was not ready? Why would they jump the gun now?

We were all excited for today, but it truly is the most ideal thing in the world to wait two more weeks so everything, including the weather, can be perfect. The delay is simply worth it. But Tesla, seriously, make this the last one.

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Elon Musk

SpaceX nails “Lucky 13” astronaut launch, leaning into Tesla tradition and superstition

SpaceX launched Crew-13 astronauts to the ISS Thursday, setting up a record fast Dragon docking.

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Crew Dragon sits atop Falcon 9 at sunrise on Cape Canaveral's pad 40, less than a day before four astronauts are set to launch to the ISS. (Credit: SpaceX)

SpaceX launched NASA’s Crew-13 mission to the International Space Station on Thursday morning, getting four astronauts to orbit despite a forecast of thunderstorms and gusty winds that had threatened to push the flight to Friday.

Falcon 9 lifted off from Space Launch Complex 40 at Cape Canaveral Space Force Station at 11:10 a.m. ET carrying Dragon Grace, NASA confirmed. On board are NASA commander Jessica Watkins, NASA pilot Luke Delaney, Canadian Space Agency astronaut Joshua Kutryk and Roscosmos cosmonaut Sergey Teteryatnikov. The first stage booster, B1101, landed at Landing Zone 40 beside the pad on its third flight after previously supporting Crew-12 and a Starlink mission.

It was the first spaceflight for Delaney, Kutryk and Teteryatnikov. Watkins, who flew on Crew-4 in 2022, became the first NASA astronaut to launch aboard a Crew Dragon twice.

Before launch, the crew rode to the pad in Teslas, a tradition on NASA’s SpaceX crew flights since 2020. This time the cars carried specialty plates reading “Lucky 13.” Watkins said the mission patch leans into the number on purpose, as a nod to Apollo 13 and the resilience of that crew.

Grace is now on a short trip to the station. Docking at the forward port of the Harmony module is scheduled for about 7 p.m. ET, roughly 7 hours and 50 minutes after liftoff, which Space.com notes would be the fastest Crew Dragon transit to the ISS yet. Most Dragon flights take around 15 to 24 hours to catch the station. Hatch opening is planned for 8:25 p.m. ET.

The launch came more than two weeks later than originally planned. An oxidizer leak was found in Grace’s propulsion system in August, and NASA and SpaceX added time for tests. That pushed back the return of Crew-12, which has been aboard the station since February and is now set to splash down off Southern California next week. Crew-13 is expected to stay about six months.

SpaceX rescue mission for stranded ISS astronauts nears end — Here’s when they’ll return home

SpaceX already holds NASA orders for crew rotations through Crew-17, while Boeing is preparing an uncrewed Starliner flight to the station as early as December.

Crew-13 was only the first of three SpaceX launches planned for Thursday, as Teslarati previewed on Wednesday. A Falcon 9 launched its Transporter-18 mission from California today, where Google will be launching its first orbital artificial intelligence (AI) test satellite. Meanwhile, Falcon Heavy is set to launch the classified NROL-97 mission for the National Reconnaissance Office from Launch Complex 39A at 11:53 p.m. ET. Its two side boosters will return to Landing Zones 1 and 2, which means Central Florida could hear up to three sonic booms in a single day. The busy stretch follows Starship’s Flight 14 on Monday, which reached orbit for the first time.

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Tesla moves forward on Wireless Charging for vehicles

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Credit: Tesla | X

Tesla has moved its Wireless Charging efforts for its electric vehicles forward, as it had a new patent published today, one that it submitted back in March.

The patent describes a system for detecting foreign objects on the wireless charging pad under varying temperatures, aiming to mitigate any undesired results that could come from something being on top of the charging pad.

The abstract of the patent states:

“The present disclosure relates to methods and systems that can reliably detect foreign objects on a wireless charging pad under varying temperatures. In some examples, an object detector can utilize a set of inductive coils included in resonant tanks, and excite the resonant tanks using signals in a range of frequencies including or near a nominal resonant frequency of the resonant tanks. The object detector can detect a metal object based on resistance of a coil increasing and inductance of the coil decreasing. By analyzing the shifts and/or distributions in resonant frequencies and output magnitudes (e.g., output voltage peaks), the object detector can distinguish between changes of frequencies and magnitudes caused by temperature and those caused by foreign objects to accurately detect the foreign objects.”

The object detection system will utilize a set of inductive coils included in resonant tanks, and “excite the resonant tank using signals in a range of frequencies including or near a nominal resonant frequency of the tanks.” Metal can be detected by an increase in the coil’s resistance and a decrease in the coil’s inductance.

By analyzing shifts or disruptions in resonant frequencies and output magnitudes, the system can detect foreign objects. These types of safeguards need to be implemented through the normal operation of the charging pads.

Tesla says its Cybercab wireless charging efficiency is ‘well above 90%’

Tesla plans to utilize wireless charging with Cybercab and Robotaxi-enabled units to help streamline the fully autonomous experience from A to Z. The last thing the company wants to do is have any sort of small obstruction preventing the rider from experiencing Robotaxi as intended.

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