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SpaceX wiggles Starhopper’s Raptor engine, tests parts ahead of hover test debut

Repeating a test conducted in June with Raptor SN04, SpaceX tested Starhopper and Raptor SN06's thrust vectoring capabilities on July 12th. (NASASpaceflight - bocachicagal)

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On the evening of July 12th, SpaceX technicians put Starhopper’s freshly-installed Raptor – serial number 06 (SN06) – through a simple but decidedly entertaining test, effectively wiggling the engine in circles.

Designed to verify that Raptor’s thrust vectoring capabilities are in order and ensure that Starhopper and the engine are properly communicating, the wiggle test is a small but critical part of pre-flight acceptance and a good indicator that the low-fidelity Starship prototype is nearing its first hover test(s). Roughly 48 hours after a successful series of wiggles, Starhopper and Raptor proceeded into the next stage of pre-flight acceptance, likely the final more step before a tethered static fire.

Routine for all Falcon rockets, SpaceX’s exceptionally rigorous practice of static firing all hardware at least once (and often several times) before launch has unsurprisingly held firm as the company proceeds towards integrated Starhopper and Starship flight tests. Despite the fact that Raptor SN06 completed a static fire as recently July 10th, SpaceX will very likely put Starhopper and its newly-installed Raptor through yet another pre-flight static fire, perhaps its fourth or fifth test this month.

Although it would undoubtedly be easier, cheaper, and faster to skip that post-delivery static fire, it will simultaneously lower the risk of Raptor failing mid-flight and verify that Starhopper itself is healthy and ready for untethered hovering. Although SpaceX could likely live without Starhopper in the event that it’s lost during flight-testing, any failure capable of destroying the vehicle itself is at least as capable of severely damaging or completely destroying the spartan but still expansive test and launch facilities the company built over the course of several months.

SpaceX has been hard at work gradually building, expanding, and upgrading its South Texas launch facilities since December 2018. (NASASpaceflight – bocachicagal, 04/27/2019)

Would you like some testing with your testing?

Follow July 12th’s nighttime Raptor wiggle test, July 13th was mainly quiet and filled with inspections of Starhopper, Raptor, and other various work. The day after, however, SpaceX proceeded through several hours of propellant loading, ending with what looked like less energetic versions of the Raptor preburner ignition tests Starhopper previously performed with Raptor SN02.

In a staged-combustion engine like Raptor, getting from the supercool liquid oxygen and methane propellant to 200+ tons of thrust is quite literally staged, meaning that the ignition doesn’t happen all at once. Rather, the preburners – essentially their own, unique combustion chambers – ignite an oxygen- or methane-rich mixture, the burning of which produces the gas and pressure that powers the turbines that bring fuel into the main combustion chamber. That fuel then ignites, producing thrust as they exit the engine’s bell-shaped nozzle.

The first obvious test occurred around 7:30pm CT, July 14th. (LabPadre)
The second obvious test followed around 8:50 pm CT. (LabPadre)

Although the fireworks are so subtle that they are easily missed, the conditions inside the preburner – hidden away from view – are actually far more intense than the iconic blue, purple, and pink flame that exists Raptor’s nozzle. This is because the preburners have to nurture the conditions necessary for the pumps they power to fuel the main combustion chamber. Much like hot water will cool while traveling through pipes, the superheated gaseous propellant that Raptor ignites to produce thrust will also cool (and thus lose pressure) as it travels from Raptor’s preburner to the main combustion chamber.

Thus, if the head pressure produced in the preburners is too low, Raptor’s thrust will be (roughly speaking) proportionally limited at best. At worst, low pressure in the preburners can completely prevent Raptor from starting and running stably and can even trigger a “hard start” or shutdown that could damage or destroy the engine. As such, to preburners fundamentally have to operate at higher chamber pressures (and thus higher temperatures) than the main combustion chamber (the big firey bit at the end). According to Elon Musk, Raptor’s oxygen preburner has the worst of it, operating at pressures as high or higher than 800 bar (11,600 psi, 80 megapascals).

Coincidentally, this is roughly equivalent to the pressure at the bottom of the Pacific Ocean.

Starhopper and Raptor seen on the afternoon of July 14th, preparing for an evening of testing. (NASASpaceflight – bocachicagal)

In short, preburner testing is no less critical than full-on static fire testing with an engine like Raptor. July 14th’s test was also made doubly efficient due to the fact that preburner testing requires liquid propellant, which effectively makes the whole test a wet dress rehearsal (WDR) even before any engine ignition or partial ignition is involved. Per SpaceX moving from propellant loading to preburner/turbine testing, Starhopper is almost certainly healthy and operating as expected, an excellent sign that the ungainly vessel may be ready for a static fire of Raptor as early as 2pm CT, July 15th.

The memes, oh, the memes.

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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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Energy

Tesla launches Powerwall Lease for affordable home backup

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Credit: Tesla

Tesla Energy has introduced the Powerwall Lease in conjunction with Tesla Electric, making the service available in Texas. This new option delivers whole-home backup power using two Powerwall units for a net monthly cost of $35 after credits, accompanied by a low fixed electricity rate.

Under the lease terms, customers pay a one-time order fee of $100. The base lease payment for the two Powerwalls is approximately $122 per month during the first year, subject to a 3 percent annual escalator thereafter. Enrollment in a qualifying Tesla Electric Backup plan or Virtual Power Plant plan provides an $87 monthly credit.

This credit lowers the effective cost to roughly $35 per month plus applicable tax.

Installation of the standard system carries no additional charge. The package features Storm Watch for outage protection and allows complete management through a single Tesla application. The system supplies continuous whole-home backup capability.

The Powerwall system enables households to maintain electricity during severe storms that disrupt the utility grid. When outages occur, the batteries automatically provide seamless backup power to the home.

Tesla announces 100k Powerwalls are participating in Virtual Power Plants

Tesla Storm Watch monitors weather forecasts and ensures the units are fully charged ahead of anticipated severe weather events so that power remains available throughout the disruption, keeping lights, refrigeration, and other essential systems operating without interruption.

Availability is restricted to select Texas locations where retail electric choice exists. Participants must lease exactly two Powerwall units and maintain continuous enrollment with Tesla Electric. Solar panels cannot be included under this particular lease arrangement.

The monthly credit activates automatically once the system is installed, receives permission to operate, and enrollment is confirmed. To retain the credit, customers are required to stay enrolled in Tesla Electric and fulfill all program conditions.

Nonstandard installations that involve electrical upgrades or special permitting may lead to extra expenses and might impact eligibility for the credit, so be sure to check with either your installer or Tesla to ensure you will still qualify.

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News

Elon Musk teases Tesla Roadster unveiling once again

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tesla roadster
Credit: Tesla

Elon Musk continues to tease the unveiling event for the Tesla Roadster, a continuing trend that has grown into a bigger game of “When” for fans who have been waiting years for the car to finally enter production.

A video shared on X of the Joe Rogan Experience podcast that Musk appeared on last year, teasing the Roadster unveiling, was shared once again on the social media platform. The poster said the Roadster event will be “unforgettable.”

Musk agreed:

The timing is interesting because just yesterday, Musk said that we will be getting flying cars, and for years, Tesla has hinted that it could develop a SpaceX cold gas thruster package that would help the car float or fly for a short period of time.

It would be reasonable to assume Tesla’s major delays with this unveiling event are likely caused by the company’s need to break the rules and push the envelope on nearly everything. Last July, Lars Moravy, Tesla’s VP of Vehicle Engineering, said:

“Roadster is definitely in development. We did talk about it last Sunday night. We are gearing up for a super cool demo. It’s going to be mind blowing. We showed Elon some cool demos last week of the tech we’ve been working on and he got a little excited.”

The latest updates that Tesla has given us are that the Roadster is in design development, and it did have several potential dates for an unveiling event this year, including April. It was then pushed to August.

However, there are no clues as to when Tesla will be ready, and fans are certainly getting frustrated with the delays.

For what it is worth, Franz von Holzhausen told Jay Leno this week that the event would be “very soon.”

We sure hope.

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Lifestyle

Tesla’s driverless Cybercab just passed a big test with State Governor

Florida’s governor rode Tesla’s Cybercab at a closed test track and called the experience impressive.

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Florida Governor Ron DeSantis rode in a Tesla Cybercab on a closed test track this week and came away impressed, posting on X that the vehicle “successfully navigated all hazards — a kid running into the street, a crash with police stopping traffic, a Model S cutting us off, etc.” He called the ride “impressive.”

The stop was part of a broader event Monday at SunTrax, a 775 acre state owned proving ground in Auburndale that Florida built specifically to test autonomous and connected vehicles before they reach public roads. Standing next to a gold Cybercab, DeSantis described the car in plain terms: “You go in there and you just sit. You have a screen. There’s no steering wheel, no pedals. Clearly these things could be very beneficial.”

DeSantis paired the praise with a caveat that has followed autonomous vehicles since the category existed. “You don’t want to be in an autonomous vehicle and it drives you into a ditch. That would not be good,” he said, framing safety validation as the gate before wider deployment.

SunTrax, the 2.25 mile oval which the state calls the only high speed autonomous vehicle test track in the Southeast, can simulate rain, pedestrian crossings, hills and crowded urban conditions at highway speeds, letting companies push a car past what an early public rollout would risk. Tesla, Waymo and Beep all use the facility, and Florida’s regulatory approach, among the most permissive for autonomous vehicles in the country, doesn’t require a human operator inside a fully autonomous car.

Tesla has reason to want the blessing of Florida and states beyond, as the Cybercab entered volume production at Gigafactory Texas this spring and has since self certified as SAE Level 4 under Texas law. Public road testing so far has kept a safety monitor in the passenger seat, and Florida is where Tesla has been expanding its existing Model Y based Robotaxi service instead, adding Miami in July and then Orlando and Tampa two weeks later. A closed track endorsement from a sitting governor doesn’t change any of that, but it does put Tesla’s newest hardware in front of a state that has already shown it will move fast on rules.

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