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SpaceX scrubs Starhopper’s final Raptor-powered flight as Elon Musk talks “finicky” igniters
For unknown reasons, SpaceX’s Starhopper prototype suffered a hold just 0.8 seconds prior to its second planned flight test, a hold that was eventually followed by a decision to scrub the August 26th attempt and try again tomorrow, August 27th.
Starhopper is a full-scale, partial-height testbed for SpaceX’s next-generation Starship launch vehicle, serving more as a semi-mobile test stand for steel rockets and Raptor engines than an actual Starship prototype. The unusual vehicle took flight for the first time ever on July 25th, reaching an altitude of roughly 20m (65 ft) under the power of a single Raptor engine, capable of producing up to 200 tons (450,000 lbf) of thrust. That test also suffered a minor scrub on the 24th, followed by a successful flight one day later, a chapter that Starhopper may now mirror on its second attempted flight, a 150m (500 ft) hop.
Notably, SpaceX CEO Elon Musk took to Twitter just seconds after the rocket’s scheduled liftoff suffered a last-second hold to indicate that Raptor’s torch igniters were proving somewhat finicky relative to the chemical alternative used by SpaceX’s proven Merlin engines.
The CEO later confirmed that that comment was directly related to the 26th’s scrub, indicating that Raptor serial number 06 (SN06) needed to have its igniters inspected prior to a second hop test attempt, now scheduled to occur no earlier than 6pm EDT (22:00 UTC) on August 27th. The gist of the difficulties with Raptor’s igniter starts with the reason that SpaceX is attempting to integrate an entirely new form of ignition into the engine, replacing the methods successfully used over tens or even hundreds of thousands of seconds of firing with the company’s Merlin 1 and Merlin Vacuum engines.
Merlin 1D and MVacD both rely on a relatively simple, reliable, cheap, and easy method of chemical ignition, using a duo of pyrophoric materials known as triethylaluminum-triethylborane (TEA-TEB). When mixed, these materials immediately combust, generating an iconic green flash visible during Falcon 9 and Heavy launches, and thus producing the ‘spark’ needed to start Merlin engines.
Generally speaking, TEA-TEB is an excellent method of igniting rockets, even if it is more of a brute-force, inelegant solution than alternatives. It does, however, bring limitations: every single ignition requires a new ‘cartridge’ be expended, fundamentally limiting the number of times Merlin 1D (and Merlin Vacuum) engines can be ignited before and after liftoff.
This doesn’t even consider the fact that TEA-TEB are extremely complex chemical products that would be next to impossible to produce off of Earth, at least for the indefinite future.
To combat these downsides, SpaceX has designed Raptor with an entirely different method of ignition, known as torch ignition. Technically speaking, Raptor’s power, design, and methalox propellant combine to demand more than a relatively common solution, in which spark plugs are used to ignite an engine. Instead, Raptor uses those spark plugs to ignite its ignition sources, what CEO Elon Musk has described as full-up blow torches. Once ignited, those blow torches – likely miniature rocket engines using the same methane and oxygen fuel as Raptor – then ignite the engine’s methane and oxygen preburners before finally igniting those mixed, high-pressure gases in the combustion chamber.
In simple terms, the fact that Raptor is a full-flow staged-combustion (FFSC) engine means that the pressures it must operate under are extreme, verging on unprecedented in large-scale rocketry. Extremely high-pressure gases (on the order of 3,000-10,000+ psi or 200-700+ bar) are just as difficult to reliably ignite, especially if hypergolic solutions (i.e. TEA-TEB) are off the table.
To get an even ignition – critical to avoid burn-through, minor explosions, and even catastrophic engine failures – Raptor’s torch ignition may actually involve a 360-degree ring of spark plug-lit torches around the point of ignition, an undeniably complex solution.
However, as Musk notes, these significant, “finicky” challenges brought on by Raptor’s exotic ignition method are motivated by the potential benefits such a solution might bring. Relative to Merlin 1D’s TEA-TEB ignition, torch ignition – once optimized and matured into a reliable solution – will permit an almost unlimited number of Raptor ignitions before, during, and after flight.
Avoiding TEA-TEB and other complex chemical igniters also means that Starship will technically be able to launch to Mars or the Moon, perform injection and landing burns, maybe even hop around the surface, and still be able to return to Earth – all without resupply. Such a return voyage would still be predicated on the ability to generate the methane and oxygen propellant needed to fuel Starships, but – assuming that challenge can be solved – torch-lit Raptors would be ready for such a mission. In the event that, say, something like August 26th’s scrub happens to a Starship on Mars, the crew would also be able to get out, inspect Starship’s Raptors, and even replace faulty spark plugs if necessary.
Technically, one could bring lots of spare TEA-TEB cartridges and install those in space or after landing, but those cartridges are quite literally firebombs waiting to ignite, whereas spare spark plugs are entirely inert.
For now, we’ll have to wait for SpaceX technicians to get their eyes and hands-on Starhopper’s lone Raptor engine to verify that its ignition hardware is in good health. If all goes well, Starhopper will attempt its final flight test as early as August 27th.
Update (August 27th): Starhopper is reportedly set for a second attempted 150m (500 ft) flight test today, scheduled to occur no earlier than 5pm EDT (21:00 UTC) on August 27th. Stay tuned for SpaceX’s official Livestream!
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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.
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:
Been getting a lot of messages from people who downloaded Tesla’s new Robtoaxi app last night and already have access to the company’s robotaxi and ride-hailing services. pic.twitter.com/xgbki1D3Lw
— Sawyer Merritt (@SawyerMerritt) September 4, 2025
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.
News
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.
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.
“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.
Elon Musk
The Boring Company begins hiring for Nashville’s Music City Loop
Tennessee Gov. Bill Lee expressed strong support for the project.
Elon Musk’s The Boring Company has started recruitment efforts for the Music City Loop, an underground tunnel system designed to link downtown Nashville with Nashville International Airport.
Tennessee Gov. Bill Lee expressed strong support for the project, describing it as a cost-free alternative to traditional mass transit systems that could ease traffic congestion in the city. Initial digging began in mid-August, with visible progress reported by September 1, as noted in a WKRN report.
Job creation and project scope
The Boring Company is currently seeking engineers, electricians, mechanics, and operations coordinators as part of its hiring drive for the Music City Loop in Nashville. Gov. Lee emphasized that unlike large-scale transit projects that typically cost billions, the tunnel system will not burden taxpayers.
“We’ve been trying to find ways, Metro Nashville has in particular, to develop transit in the city for a long time. It costs billions and billions of dollars to build out transit systems. We now have an opportunity to have a transit system that costs the taxpayers nothing,” Lee said, calling the effort the fast lane to the city’s future.
The Music City Loop aims to provide a quick and efficient link between the city center and the airport, similar to The Boring Company’s other tunnel projects like the Las Vegas Convention Center Loop. Officials have praised the company for cooperating with state permitting and regulatory requirements, suggesting that the Nashville Loop project is advancing in line with established processes.
Community reactions and concerns
While officials are optimistic, community response has been mixed. Some residents have raised concerns about the speed of approval and a lack of public discussion before construction began.
Nashville resident Taylor John cited environmental impacts and worries that the tunnel could primarily serve tourists rather than local commuters. “I have a lot of concerns, first of all, by how fast this decision was made, I don’t think there was a lot of discussion from the members of the community before this decision was made. It’s going to impact us,” the resident stated.
Others, however, see the project as an innovative leap forward. “There’s a whole untapped potential underneath our feet,” resident Nathaniel Lehrer stated. “Anything that can save time when picking up family or friends or you need to catch a flight, it’d be an awesome option to have.”
Tesla is already giving Robotaxi privileges hours after opening public app
Tesla explains why Robotaxis now have safety monitors in the driver’s seat
The Boring Company begins hiring for Nashville’s Music City Loop
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