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NASA scrubs first SLS Moon rocket launch attempt

A beautiful start to an unfortunately unfruitful day. (Richard Angle)

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NASA has scrubbed the first attempted launch of its Space Launch System (SLS) Moon rocket after running into multiple issues, one of which could not be solved in time.

The delay is bad news for the tens to hundreds of thousands of tourists who traveled to Cape Canaveral, Florida to witness the launch in person. Worse, by NASA’s own implicit admission, there’s a good chance the main problem SLS encountered could have already been dealt with and rectified in advance of the launch attempt if the space agency had finished testing the rocket earlier this summer.

Ultimately, that omission turned the first SLS launch attempt into more of a continuation of the rocket’s first four wet dress rehearsal (WDR) attempts, none of which ended as expected. NASA engineers will now have to decide how to proceed and whether the SLS rocket can be made ready in time for another launch attempt on September 2nd or 5th. If not, the next opportunity could be weeks away.

As far as SLS test operations go, the August 28/29th launch attempt was fairly ordinary, with the rocket running into multiple issues – a few minor, a few significant, and one identical to a previous problem. The first problem – a hydrogen leak near the SLS rocket’s base – came after a risk of lightning delayed the start of propellant loading by more than an hour. A very similar, if not identical, hydrogen fuel leak had already occurred during official wet dress rehearsal testing in April and July.

That leak was fixed on the fly by properly chilling all related systems, and propellant loading was eventually completed – albeit a few hours late thanks to inclement weather. Shortly after, there were reports of a crack that needed careful analysis. Only later did NASA specify that the suspected crack was in the rocket’s foam insulation rather than its structures, the latter of which could have been a catastrophic problem.

Around the same time, the true showstopper of the day occurred when NASA attempted to chill the SLS Core Stage’s four RS-25 engines, all of which flew several times aboard reusable Space Shuttle orbiters. Three engines performed (mostly) as expected, flowing a bit of liquid hydrogen fuel to cool themselves down, but one – engine #3 – was never able to make progress toward the optimal temperature needed for ignition (~5°C/~41°F). After hours of remote troubleshooting attempts, no progress had been made, and NASA ultimately decided to scrub the launch attempt at T-40 minutes to liftoff.

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Over the course of four separate wet dress rehearsal attempts in April and June 2022, NASA was never able to test the core stage’s engine chill capabilities. In a post-scrub press conference, Jim Free – NASA’s Associate Administrator of the Exploration Systems Development Division – revealed that all four engines were warmer than intended, further confirming that skipping a fully nominal wet dress rehearsal was likely a mistake. Clear and present evidence aside, Free stated that he and other executives still believed skipping that test was the right decision, claiming that ending explicit WDR testing reduced the number of times the rocket needed to be moved on its transporter.

Making the situation even harder to explain, Artemis I Mission Manager Mike Sarafin revealed in the conference Q&A that Boeing had changed the design of parts of the SLS engine chill (bleed) system after the Core Stage finally conducted a nominal static fire test at Mississippi’s Stennis Space Center. Completed in March 2021, the SLS rocket then sat inside NASA’s Kennedy Space Center, Florida Vehicle Assembly Building (VAB) for a full year before attempting its first wet dress rehearsal tests at the launch pad.

The first round of three WDRs were not as smooth as NASA expected and instead uncovered three relatively small issues: a hydrogen leak, a single faulty upper stage valve, and problems with a ground supply of nitrogen gas. Those small issues led NASA to roll SLS back to the VAB for repairs, incurring a minimum multi-week delay that stretched into two months. SLS also failed to complete a fourth WDR attempt in July 2022, but NASA decided to overlook the rocket parts and phases of preflight operations that were never actually tested as planned, one of which was the engine chill system.

If NASA cannot fix the RS-25 chill system within the next few days, it will be forced to roll the entire rocket and mobile launch platform back to the VAB to – at a minimum – replace its flight termination system (FTS). The US Eastern Range requires that all rocket FTS systems be tested no more than 15 days before launch, and NASA was able to secure special permission for a gap of up to 25 days. However, because Boeing’s Core Stage design places the FTS system in a location that is reportedly inaccessible at the pad, the entire SLS rocket will need to roll back to the VAB to have its FTS systems “retested” after that period.

As a result, NASA’s SLS launch debut will be delayed by several weeks (at best) if it can’t recycle for another attempt on September 2nd or 5th. The next window runs from September 20th to October 4th, but the SLS rocket took 10 days to go from its latest rollout to first launch attempt – a figure that doesn’t include the time required to remove the rocket from the pad, roll it back to the VAB, and conduct any necessary repairs or tests while back in the bay. If NASA can’t fix the engine problem at the pad by September 3rd or 4th, the true delay could be more like 4-6 weeks.

With any luck, that won’t happen, but it’s clear that a lot of stress and discomfort could have been avoided if NASA had gone into its first launch attempt knowing that its SLS rocket was truly ready.

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(Richard Angle)
(Richard Angle)
(Richard Angle)

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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How SpaceX Is raising Raptor’s sea-level thrust while holding engine mass steady

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Credit: SpaceX

SpaceX’s Raptor engine family has steadily increased sea-level thrust while simultaneously reducing mass, turning iterative engineering gains into substantially higher performance for the Super Heavy booster. CEO Elon Musk shed more light on how powerful Raptor 4 will be, and it’s pretty crazy.

Raptor 1 delivered 185 metric tons of thrust at roughly 2,080 kilograms, while Raptor 2 raised that to 230 tons while cutting mass to about 1,630 kilograms. SpaceX data for Raptor 3 lists a target of 280 tons at 1,525 kilograms (with further reductions in associated vehicle hardware), while operational flight ratings have been cited near 250 tons.

This morning, Elon Musk stated that Raptor 4 is expected to reach 300 tons of sea-level thrust at roughly the same mass as Raptor 3. Across these versions, thrust has risen by more than 60 percent from the first engines while engine mass has fallen, producing a sharp improvement in thrust-to-weight ratio. This is a true testament to how great SpaceX engineering has been:

With 33 engines on SuperHeavy, the jump from earlier versions to a 300-ton Raptor 4 would produce roughly 9,900 metric tons of total liftoff thrust, nearly three times the Saturn V’s approximately 3,400 metric tons from its five F-1 engines.

This is not just a larger number on a data sheet, either, as sea-level thrust is the force available the moment the vehicle leaves the pad. This is when it is heaviest and still deep in Earth’s gravity well and dense atmosphere.

Higher levels of sea-level thrust directly improves the initial thrust-to-weight ratio of the full stack. A higher ratio produces faster acceleration off the pad, which shortens the time the rocket has to spend fighting gravity, and gravity losses during the first minute or two of the flight are a major drain on total available delta-v. Every second shaved off of that early climb preserves more propellant energy for reaching orbital velocity or for carrying extra payload.

Because Super Heavy’s engine count is constrained by vehicle diameter and packing density, increasing thrust per engine is the most straightforward way to raise total liftoff performance without redesigning the booster structure or design.

The same-mass target for Raptor 4 is equally important. Holding engine mass roughly constant while raising thrust improves the engine’s own thrust-to-weight ratio and reduces the structural and propellant mass fraction that must be carried solely to support the engines.

Earlier Raptor iterations also simplified or eliminated extensive vehicle-side hardware such as heat shields. These gains compound: more force for less installed mass leaves additional capacity for propellant, payload, or operational margins such as engine-out capability.

For Starship’s architecture, the practical effects are large. Greater liftoff thrust supports heavier vehicles, larger propellant loads, and higher payloads to low Earth orbit, figures SpaceX has targeted in the 100-plus-ton reusable range. That capacity underpins orbital refueling, lunar missions, and eventual Mars cargo and crew flights.

Continued growth in sea-level thrust therefore tightens the gap between theoretical rocket performance and the high flight rates and reusability needed to make large-scale space transport practical.

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Tesla Assisted Driving expands to tenth EU country

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Tesla has expanded its Tesla Assisted Driving (TAD) suite to its tenth European country, as Latvia joined a growing list of European Union member states authorizing the company’s advanced driver assistance technology.

Tesla Europe announced this morning that the system is now approved in Latvia, with a software rollout to begin soon.

The approval and rollout follow recognition of a provisional European type approval originally granted by the Netherlands’ RDW authority on April 10.

Latvia’s Road Traffic Safety Directorate (CSDD) evaluated the Dutch documentation, coordinated with the other national authorities, and reviewed updates from Tesla. These included tightened limits on speed offsets, automatic resets of any manual speed adjustments after each trip, and stronger driver monitoring.

In Europe, the feature is marketed as Tesla Assisted Driving after a recent rule change that labeled the name “Full Self-Driving” as misleading.

Tesla starts showing how FSD will change lives in Europe

The system remains an SAE Level 2 driver assistance tool, not unsupervised autonomy. It can control speed, steering, braking, lane changes, and intersections while following a navigation route. Drivers need not keep their hands on the wheel at all times, yet they must continuously monitor the road and be prepared to intervene immediately.

The sequence of EU recognitions began with the Netherlands in April and continued through Lithuania, Estonia, Denmark, Belgium, Slovenia, Czechia, Croatia, and Slovakia. Most have relied on mutual recognition of the single Dutch provisional approval rather than independent national testing.

These national clearances do not yet constitute bloc-wide authorization. An EU-wide decision requires a qualified majority in the Technical Committee on Motor Vehicles: at least 15 of 27 member states representing 65 percent of the EU population. Larger markets, like Germany, France, and Italy, remain under review, and a vote is expected this December.

However, for Latvian Tesla owners with compatible vehicles and software, the imminent rollout expands access to the supervised system while underscoring that attentive human oversight remains essential.

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Tesla expands Robotaxi geofence in Houston with an ode to SpaceX merger

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Tesla expanded its Robotaxi geofence in Houston, Texas, today, enlarging the service area and drawing a new rocket-shaped boundary across the city’s northwestern and central parts.

Although CEO Elon Musk said it was just a coincidence, the expansion seems to be an ode to SpaceX and its potential merger with Tesla.

The official Tesla Robotaxi account announced the change with the lines “Houston, we have liftoff” and “Bigger service area now live,” pairing them with a map overlay.

The prior white geofence, roughly 25 square miles covering Jersey Village, Harvest Bend, and the Willowbrook corridor along U.S. 290 and State Highway 249, now sits inside a larger blue zone that stretches southeast toward Bellair and closer to central Houston.

Houston’s Robotaxi service launched on April 18, 2026, the same day as Dallas, as Tesla’s first unsupervised public expansion beyond Austin. From the start, the vehicles were Model Ys running without anyone in the front seats, booked through the dedicated Tesla Robotaxi app and open to the public inside the geofence.

Trackers measured the initial zone at about 25 square miles; by late September it had not grown substantially. Community and registry data indicated a modest local fleet of unsupervised Model Ys, while dozens to nearly 200 Cybercabs, the purpose-built, steering-wheel-free two-seaters, have been spotted staging and testing in Houston lots, though public Cybercab rides remain limited to Austin for now.

Across the broader Robotaxi program, Tesla began public Robotaxi rides in Austin in June 2025, as a small geofence and vehicles with safety monitors became available for a ride-hailing service. Later on, Tesla removed the monitors and steadily expanded the service area until it covered most of the Austin metro area.

Unsupervised Robotaxi services now run in six cities: Austin, Dallas, Houston, Miami, Orlando, and Tampa. Cumulative driverless miles reported by the company have reached several million. The Cybercab entered public service in Austin in early September 2026 and has scaled rapidly there. The company has also said that Dallas is next for Cybercab rides in November, with further cities and 24/7 hours targeted by year-end, plus fleet-operator sales of the vehicle.

Waymo also operates a fully driverless service in Houston, which has been open to the public since August of this year.

The Houston expansion continues Tesla’s pattern of starting with tightly controlled validation zones before widening coverage as real-world data accumulates, while the rocket motif on the map underscores the company’s habit of injecting visual flair into its autonomy rollout.

Riders inside the new boundary can request unsupervised Model Y trips in the Robotaxi app; exact operating hours and further Cybercab availability remain subject to app updates and company statements.

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