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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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Waymo temporarily halts service in select San Francisco and LA areas amid protests

The suspensions came after several Waymo Jaguar I-Pace robotaxis were vandalized and set ablaze during the demonstrations.

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Credit: ABC7/YouTube

Waymo, Alphabet’s autonomous vehicle subsidiary, has suspended its driverless taxi operations in parts of Los Angeles and San Francisco amid violent protests linked to U.S. Immigration and Customs Enforcement (ICE) raids in the state. 

The suspensions came after several Waymo Jaguar I-Pace robotaxis were vandalized and set ablaze during the demonstrations.

Waymo Catches Strays Amid Anti-ICE Protests

Protests erupted in Los Angeles and San Francisco in response to the Trump administration’s immigration raids, which ultimately resulted in California Governor Gavin Newsom calling the White House’s deployment of National Guard troops unconstitutional. 

Amidst the protests, images and videos emerged showing several Waymo robotaxis being defaced and destroyed. At least five Waymo robotaxis ended up being caught in the crossfire, and at least one vehicle ended up being burned to the ground. 

The incident resulted in the Los Angeles Police Department advising people to avoid downtown areas due to toxic fumes from the robotaxis’ burning lithium-ion batteries. As noted in a KRON4 report, Waymo ultimately halted service in affected areas “out of an abundance of caution.”

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Robotaxi Sentiments

The cost of the attacks is notable. Each Waymo robotaxi is valued between $150,000 and $200,000, per a 2024 Wall Street Journal report. Interestingly enough, this is not the first time that Waymo’s robotaxis ended up on the receiving end of angry protesters. On February 24, a Jaguar I-PACE robotaxi was set ablaze and vandalized by a crowd in San Francisco. Videos taken at the time showed a mob of people attacking the vehicle. 

Despite the recent attacks on its robotaxis, Waymo has stated it has “no reason to believe” its vehicles were specifically targeted during the protests, as per a report from The Washington Post. A company spokesperson also noted that some of the Waymo robotaxis that were defaced and destroyed during the violent demonstrations had been completing drop-offs near the protest zones.

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Investor's Corner

xAI targets $5 billion debt offering to fuel company goals

Elon Musk’s xAI is targeting a $5B debt raise, led by Morgan Stanley, to scale its artificial intelligence efforts.

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(Credit: xAI)

xAI’s $5 billion debt offering, marketed by Morgan Stanley, underscores Elon Musk’s ambitious plans to expand the artificial intelligence venture. The xAI package comprises bonds and two loans, highlighting the company’s strategic push to fuel its artificial intelligence development.

Last week, Morgan Stanley began pitching a floating-rate term loan B at 97 cents on the dollar with a variable interest rate of 700 basis points over the SOFR benchmark, one source said. A second option offers a fixed-rate loan and bonds at 12%, with terms contingent on investor appetite. This “best efforts” transaction, where the debt size hinges on demand, reflects cautious lending in an uncertain economic climate.

According to Reuters sources, Morgan Stanley will not guarantee the issue volume or commit its own capital in the xAI deal, marking a shift from past commitments. The change in approach stems from lessons learned during Musk’s 2022 X acquisition when Morgan Stanley and six other banks held $13 billion in debt for over two years.

Morgan Stanley and the six other banks backing Musk’s X acquisition could only dispose of that debt earlier this year. They capitalized on X’s improved operating performance over the previous two quarters as traffic on the platform increased engagement around the U.S. presidential elections. This time, Morgan Stanley’s prudent strategy mitigates similar risks.

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Beyond debt, xAI is in talks to raise $20 billion in equity, potentially valuing the company between $120 billion and $200 billion, sources said. In April, Musk hinted at a significant valuation adjustment for xAI, stating he was looking to put a “proper value” on xAI during an investor call.

As xAI pursues this $5 billion debt offering, its financial strategy positions it to lead the AI revolution, blending innovation with market opportunity.

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SpaceX to debut new Dragon capsule in Axiom Space launch

Ax-4’s launch marks the debut of SpaceX’s latest Crew Dragon and pushes Axiom closer to building its own space station.

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spacex-dragon-axiom-ax-4-mission-iss
(Credit: SpaceX)

Axiom Space’s Ax-4 mission targets the International Space Station (ISS) with a new SpaceX Crew Dragon capsule.

The Axiom team will launch a new SpaceX Dragon capsule atop a Falcon 9 rocket from NASA’s Kennedy Space Center in Florida on Wednesday at 8:00 a.m. EDT (1200 GMT). The Ax-4 mission launch was initially set for Tuesday, June 10, but was delayed by one day due to expected high winds.

As Axiom Space’s fourth crewed mission to the ISS, Ax-4 marks the debut of an updated SpaceX Crew Dragon capsule. “This is the first flight for this Dragon capsule, and it’s carrying an international crew—a perfect debut. We’ve upgraded storage, propulsion components, and the seat lash design for improved reliability and reuse,” said William Gerstenmaier, SpaceX’s vice president of build and flight reliability.

Axiom Space is a Houston-based private space infrastructure company. It has been launching private astronauts to the ISS for research and training since 2022, building expertise for its future station. With NASA planning to decommission the ISS by 2030, Axiom has laid the groundwork for the Axiom Station, the world’s first commercial space station. The company has already begun construction on its ISS replacement.

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The Ax-4 mission’s research, spanning biological, life, and material sciences and Earth observation, will support this ambitious goal. Contributions from 31 countries underscore the mission’s global scope. The four-person crew will launch from Launch Complex 39A, embarking on a 14-day mission to conduct approximately 60 scientific studies.

“The AX-4 crew represents the very best of international collaboration, dedication, and human potential. Over the past 10 months, these astronauts have trained with focus and determination, each of them exceeding the required thresholds to ensure mission safety, scientific rigor, and operational excellence,” said Allen Flynt, Axiom Space’s chief of mission services.

The Ax-4 mission highlights Axiom’s commitment to advancing commercial space exploration. By leveraging SpaceX’s Dragon capsule and conducting diverse scientific experiments, Axiom is paving the way for its Axiom Station. This mission not only strengthens international collaborations but also positions Axiom as a leader in the evolving landscape of private space infrastructure.

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