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SpaceX’s orbital Starship prototype gets frosty during first successful ‘cryoproof’

Starship S20 lets off some steam with a vent 200+ feet long during its first cryoproof test. (NASASpaceflight - bocachicagal)

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For the first time, SpaceX has put the first orbital-class Starship – a prototype known as Ship 20 (S20) – through a routine cryogenic proof test, filling the rocket with several hundred tons of liquid nitrogen to simulate its explosive propellant.

While it’s impossible to jump to conclusions before members of the public can return to the pad to take photos or CEO Elon Musk takes to Twitter to discuss the results, Ship 20’s first ‘cryoproof’ appears to have been largely successful [Edit: Musk has confirmed that the test went well]. Relative to the almost three-dozen cryoproofs SpaceX has completed with more than a dozen other Starship, booster, and test tank prototypes over the last two years, though, Ship 20’s first major test still has some oddities.

Historically, every cryoproof of a full Starship prototype has been visually unique and virtually impossible to predict. Without any direct insight from SpaceX or Elon on the objectives, plan, or timeline of tests, the process of watching tests (via unofficial webcams, of course) and attempting to interpret why certain things look the way they do or what’s going on at any given moment is a bit trying to interpret eroded hieroglyphics.

At the most basic level, cryogenic tanking tests – whether with Starship, Super Heavy, or test tanks and liquid oxygen (LOx)/methane (LCH4) propellant or neutral liquid nitrogen (LN2) – are fairly simple. The vehicle is attached to pad systems, powered on, and partially or fully loaded with cryogenic fluids. Once the desired test objectives are achieved or attempted, the vehicle is then detanked (drained of propellant or LN2).

Thanks to the fact that they’re incredibly cold (-160 to -200C; -260 to -330F), the LOx/LCH4 or LN2 Starships are filled with quickly chill the thin steel tanks containing them. With no insulation to speak of, that supercooled steel then freezes water vapor out of the humid South Texas air, creating a layer of frost/ice that generally follows the level of the cryogenic liquids in Starship’s tanks. Throughout that process, those cryogenic liquids inevitably come into contact with ambient-temperature Starship tanks and plumbing (white-hot in comparison) and warm up, boiling off into gas as a result.

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A gaseous chemical is far less dense than its liquid form, meaning that the pressure inside Starship’s fixed tanks can rapidly become unmanageable after even a small amount of boiloff. To maintain the correct tank pressures, Starship – like all other rockets – occasionally vents off the gas that forms. And thus, the two main methods of interpreting the hieroglyphics that are cryoproof tests: frost levels and venting.

Compared to earlier prototypes, Starship S20’s first cryoproof has been… unusual. Most notably, SpaceX began loading the rocket with liquid nitrogen around 8pm CDT. Its LOx (bottom) and CH4 (top) tanks were then slowly filled to around 30-50% of their full volume over the next hour. However, rather than detanking, SpaceX then partially drained the methane tank but filled the LOx tank further before leaving the LOx tank more or less fully filled for more than two hours, occasionally topping it off with fresh liquid nitrogen.

Several giant vents almost four hours after testing began tricked even the most experienced of ‘Tank Watchers.’

Then, almost four hours after LN2 loading began, Starship performed several massive vents. Ordinarily, given the hours of testing prior, those vents would have assuredly been detank vents – effectively depressurizing Starship’s tanks as they’re drained of fluid. However, those vents instead coincided with the rapid loading of one or several hundred more tons of LN2, seemingly topping off Starship S20 in the process. Around that point, it’s possible that SpaceX began the pressure testing portion of Ship 20’s cryoproof, (mostly) closing the rocket’s vents and allowing the pressure to gradually increase to flight levels (and maybe even higher).

Many, many months ago, when SpaceX was deep into cryoproofing the first full-size Starship prototypes, Musk revealed an operating pressure goal of 6 bar (~90 psi). Ships were eventually successfully tested above 8 bar (~115 psi), giving Starship a healthy ~30% safety margin. As the first orbital-class Starship prototype, Ship 20 likely needs to hit those tank pressures more so than any ship before it to have a shot at surviving its orbital launch debut and orbital-velocity reentry attempt.

Starship S20’s first (aborted) cryogenic proof test attempt, September 27th. (NASASpaceflight – bocachicagal)
A demonstration of the kind of forces and pressures involved with SpaceX’s building-sized Starship SN1 prototype in February 2020.

Beyond the basics of cryoproofing, Starship S20 also marked a crucial step forward on September 29th/30th, becoming the first ship to complete a cryoproof test with a full heat shield installed. While it’s impossible to judge exactly how well S20’s ~15,000-tile heat shield performed, views from public webcams showed no obvious signs of tiles shattering and falling off as Starship repeatedly cooled and warmed – contracting and expanding as a result. Additionally, still in contact with the air, the steel tank skin under a majority of Ship 20’s tiles would have likely covered itself in a layer of frost and ice, but the heat shield appeared to handle that invisible change without issue.

It’s possible that dozens or hundreds of tiles bumped together and chipped or cracked in a manner too subtle to be visible on LabPadre or NASASpaceflight webcasts, but that can only be confirmed or denied when the road reopens and local photographers can capture higher-resolution views of Starship. For now, it appears that Ship 20’s first cryoproof was highly successful, hopefully opening the door for Raptor installation and static fire testing in the near future. Stay tuned for more!

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Update: As is almost tradition by now, SpaceX CEO Elon Musk didn’t take long to tweet about the results of Starship S20’s first cryoproof, confirming that the “proof was good!”

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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Elon Musk says Tesla will take Safety Drivers out of Robotaxi: here’s when

“The safety driver is just there for the first few months to be extra safe. Should be no safety driver by end of year.”

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Credit: Joe Tegtmeyer | X

Tesla CEO Elon Musk said today that the company plans to completely eliminate Safety Drivers from its Robotaxi fleet, which differs from the Safety Monitors it uses.

Tesla’s Robotaxi platform utilizes employees in the front passenger seat during city rides in Austin and the driver’s seat of the vehicles during highway operations in Austin, as well as during all rides in the Bay Area.

Tesla adjusts Robotaxi safety monitor strategy in Austin with new service area

Musk said the presence of a Safety Driver “is just there for the first few months to be extra safe,” but there are plans to remove them in an effort to remove the crutches the company uses during the early stages of Robotaxi.

The CEO then outlined a timeframe for when it would remove the presence of an employee in the driver’s seat in both Austin and the Bay Area. He said there “should be no safety driver by end of year.”

Having a Safety Driver or Monitor has been a major point of criticism from Robotaxi skeptics and Tesla critics.

However, Tesla has maintained that its priority in the early stages is the safety of riders, which will keep things running; even a single negative incident could derail self-driving efforts as a whole, including those outside of the company.

Tesla executives have said their attitude toward safety is “paranoid,” but for good reason: an accident could set back the progress that it and many other companies, including rivals like Waymo, have made in the past few years.

For now, it might be a point of criticism for some, but it’s smart in the near term. Musk plans for Tesla to have Robotaxi operating for half of the U.S. population by the end of the year as well, so it will be interesting to see if it can maintain these timelines.

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Tesla is already giving Robotaxi privileges hours after opening public app

This morning, Tesla launched the app in the Apple Store, giving iOS users the ability to download and join a waitlist in hopes of gaining access.

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tesla robotaxi app on phone
Credit: Tesla

Tesla is already giving Robotaxi privileges to those who downloaded the app and joined its waitlist just hours after it launched in the United States.

As the Robotaxi platform has been operating in Austin for several months, Tesla is now allowing the general public to download its app and call for a driverless ride in the city.

Tesla Robotaxi makes major expansion with official public app launch

The company previously sent invitations to select media outlets and Tesla influencers, seeking initial feedback on the performance of the Robotaxi platform.

There have been positive reviews, but, as with any Beta program, some mishaps have also occurred, although none have been significant.

As of the writing of this article, the City of Austin only lists one incident involving a Tesla Robotaxi, noting it as a “Safety Concern,” but not an accident or collision.

This morning, Tesla launched the app in the Apple Store, giving iOS users the ability to download and join a waitlist in hopes of gaining access.

Tesla is already granting Robotaxi access to several of those who have downloaded the app and gotten on the waitlist early:

With the launch of the public app, we were not too sure how soon Tesla would be able to initiate bringing more riders into the Robotaxi program. The immediate admittance for some riders just hours after the launch is a big positive and is surely a sign of strength for Tesla and its Robotaxi program.

What many will look for moving forward is the expansion of the geofence, which does not seem like a problem, as Tesla has already managed to do this on three occasions. The most recent expansion has expanded the service area to approximately 190 square miles.

People will also look for evidence of fleet expansion, a concern that has been a concern for many, especially since Tesla has not been completely transparent about it. They have revealed a recent service fleet growth of 50 percent, but there has been no specific number of vehicles mentioned.

Tesla reveals it has expanded its Robotaxi fleet in Austin

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Tesla explains why Robotaxis now have safety monitors in the driver’s seat

The update to Austin’s safety monitors became a point of interest among Tesla watchers on social media.

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Credit: Tesla

Tesla has provided an explanation about the presence of safety monitors in the driver’s seat of its autonomous Robotaxi units.

The autonomous ride-hailing service is currently being deployed in Austin and the Bay Area, with more cities across the United States expected to gain access to the service later this year.

Safety Monitors

When Tesla launched its initial Robotaxi program in Austin, the company made headlines for operating vehicles without a human in the driver’s seat. Even with this setup, however, Tesla still had safety monitors in the passenger seat of the Robotaxis. The safety monitors, which do not interact with passengers, have been observed to report issues and other behaviors from the autonomous vehicles in real time. 

Safety monitors on the driver’s seat were also employed in the service’s Bay Area rollout, though numerous members of the EV community speculated that this was likely done to meet regulations in California. However, with the expansion of the Austin geofence, riders in Tesla’s Robotaxis observed that the safety monitors in the city have been moved to the driver’s seat as well.

Tesla’s explanation

The update to Austin’s safety monitors became a point of interest among Tesla watchers on social media. Longtime FSD tester Whole Mars Catalog, for one, speculated that the move might be due to Texas’ new regulations for autonomous vehicles, which took effect recently. Interestingly enough, the official Tesla Robotaxi account on X responded to the FSD tester, providing an explanation behind the safety monitor’s move to the driver’s seat. 

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“Safety monitors are only in the driver’s seat for trips that involve highway driving, as a self-imposed cautious first step toward expanding to highways,” the Tesla Robotaxi account noted.

Tesla has been extremely cautious with its autonomous driving program, particularly with the rollout of its Robotaxi service, which use Unsupervised FSD. This is quite understandable considering the negative media slant that Tesla is consistently subjected to, which could very well result in minute incidents or mistakes by Robotaxis being blown out of proportion.

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