On March 7, 2025, SpaceX performed the eighth test launch of the Starship, which failed. After eight minutes of flight, the ship lost control, communication was cut off, and the vehicle disintegrated about 145 km above the Caribbean Sea. This is the second accident in a row: in January (Flight 7), Starship also crashed due to a similar problem with an engine section. We collected official and insider information and conducted a technical analysis of the possible causes of the crash.
Official data and results of previous investigations
Immediately after the crash, SpaceX confirmed that the Starship had been destroyed in flight and the company and regulators launched an investigation into the incident. No detailed information about the causes of the Flight 8 crash was publicly disclosed at the time of the incident – SpaceX only noted that engineers were analyzing telemetry to determine the root cause, emphasizing: “success comes through the lessons we learn”. With this wording, the company recognized the RUD (Rapid Unscheduled Disassembly) of the ship and the need for technical improvements before the next launches.
It is known that the seventh test flight of the Starship (January 16, 2025) ended in a similar failure: the upper stage also disintegrated about 8 minutes after launch. SpaceX’s investigation has determined the cause of that accident. According to the official report, the flight caused a harmonic resonant load on the power elements of the engine system, which was much higher than expected based on ground tests. These abnormal harmonic oscillations led to damage in the fuel supply lines, including methane leaks that caused fires in the Starship’s engine compartment. The flames in the unpressurized “attic”* between the fuel tanks and the heat shield disabled most systems: almost all engines shut down in an emergency, except for one, after which the ship lost control and communication with it was lost in a few seconds. The autonomous flight termination system detonated the malfunctioning vehicle according to protocol to prevent uncontrollable debris from falling.
*Attic – in the context of aircraft or missile technology, means an unpressurized compartment or cavity. It is a space used to accommodate piping, wiring, or other auxiliary systems. Typically, such areas can accumulate hot gases or contribute to the spread of flames in the event of a fire, which can lead to the failure of critical systems.
SpaceX introduced several changes (which we described in more detail in the article “How engineers prepared Starship for a new flight and why explosions lead to progress”) before the next launch: it conducted a 60-second test of the engines on the bench, made hardware changes to the fuel lines of the vacuum engines, adjusted the fuel cooling modes and limited the maximum thrust level.
In addition, the “attic” ventilation system was modernized by installing additional exhaust valves and nitrogen purging to inertly extinguish possible leaks.
Causes of the Starship Flight 8 crash
Despite the measures taken, Flight 8 repeated the fate of its predecessor. The live stream showed how the number of Starship engines running decreased during the ascent, indicating that some of the Raptors had been shut down prematurely. Forums and specialized communities immediately hypothesized that the reasons could be the same as in the January flight. Later, this version was confirmed by insider information. A detailed description was posted online, citing a source close to the investigation (this insider had previously published a photo of the damaged engine compartment of the Starship S34 after the explosion).
The data he provided is largely consistent with the official findings on Flight 7 and allows for a deeper understanding of the technical side of the problem.
According to this unofficial leak, Flight 8’s telemetry showed a recurrence of the “S33 effect,” the same anomaly that happened to the ship’s serial number 33 during Flight 7. The main factor was again harmonic oscillations in the methane supply system. It is believed that the problematic link is the innovation of the Starship V2 version – vacuum-insulated fuel lines to the Raptor vacuum engines (RVac). These are double heat-insulated pipes that are laid through the oxidizer tank to power the three vacuum engines on the upper stage. In the V2 modification, the total fuel supply was increased by about 25%, the piping scheme was changed, and additional lines and joints appeared. As a result, the structure became less rigid, and during the flight, a resonance appeared in it that had not been previously recorded in tests. The standard exhaust valves and the nitrogen fire extinguishing system did not have time to remove and dilute the combustible gases – the leakage volume exceeded their capabilities, just as it had happened during the previous accident.
This time, the effects of the resonance were more fatal. While on Flight 7, one of the six Starship propulsion systems was still operating until the end of the flight, during Flight 8, an earlier critical failure probably occurred. Oscillations in the fuel lines caused them to rupture in the lower part (near the RVac engines). The moment when the main liquid oxygen tank was almost empty was especially dangerous: while the tank was full, the liquid column dampened vibrations, but as the fuel burned out, the pipelines were left without a “damper” and the amplitude of vibrations increased dramatically. As a result, several methane fuel lines were depressurized at once. High-pressure methane rushed into the inter-tank compartment, causing a rapid fire outbreak. It is likely that the blast wave at that moment ruptured the turbopump unit (TU) of one of the vacuum Raptors and damaged the adjacent central engine. Damage to the nozzle regenerative cooling system (which removes heat through the circulation of fuel in the chamber walls) was the “fatal blow” to the engines – almost instantly they all lost thrust and went out. The ship was left without active stabilization and began an uncontrolled rotation, which was recorded on the telemetry video. Then, as stipulated by the protocol, the emergency detonation system eliminated the vehicle at a high altitude.
Although these details have not yet been officially confirmed, the likelihood of such a scenario is high. The factors mentioned above must coincide with the previously identified problems at the previous launch. Moreover, there are currently few alternative hypotheses. The first telemetry analyses did not reveal that the accident was caused by, say, a specific engine malfunction or control system error; on the contrary, the failure was simultaneous for several engines and was caused by a factor external to them. We can also reject the version that the first stage flame impacted the second stage during the turnaround maneuver: during hot stage separation, the Super Heavy jet could theoretically damage the ship’s hull or equipment, but in this case, there were no signs of such damage. Instead, the hot separation mode could have indirectly aggravated the situation – it creates an additional dynamic load on the tail section, which may have increased the oscillations of the pipelines. In any case, the main theory is that it was the resonant vibration of the V2 ship’s structure that caused the cascading failures.
The technical aspect and similarity to the “pogo oscillation”
In rocketry, there have been cases of “pogo oscillations” when fluctuations in fuel pressure resonate with mechanical vibrations of the body. Such phenomena occurred in the Saturn V and the Soviet super-heavy rocket N1, leading to accidents. In Starship, these fluctuations are amplified by:
- The V2 architecture, where the fuel lines to the vacuum Raptors are moved further from the center and have complex insulation.
- Hot staging, which increases the dynamic load at the junction of the stages.
- Two types of motors in the upper stage (atmospheric and vacuum) with different feeding schemes.
Compared to the massive first stage of the Super Heavy, the second stage is lighter and less rigid, which increases the risk of unforeseen resonances.
Why did the Starship accident happen again?
Before Flight 8, SpaceX modernized certain components: changed the piping and improved the fire extinguishing system in the stern. But the short time between the two flights probably did not allow for proper testing of the complex innovations. On the ground stands, the oscillations may not have been as strong as in real flight when the pressure in the tanks was reduced.
Due to the short interval between launches, engineers did not have time to conduct a full series of long burns to simulate new modes, and the Starship S34 assembly was rushed. As a result, the “old” resonance reappeared during Flight 8, with the fire breaking out on an even larger scale due to the rupture of additional lines.
A potential “fundamental” miscalculation
Some experts suggest that the problem is not localized, but is inherent in the very idea of diluting the Starship V2 fuel systems. The design has the following vulnerabilities:
- The piping runs through the LOX tank, saving space but making damping more difficult.
- Vacuum insulation creates conditions for the accumulation of resonant waves.
- The pace of the tests does not allow us to fully test the modifications.
If this hypothesis is confirmed, SpaceX will have to radically change the layout of the engine section to avoid a recurrence of accidents.
Possible consequences and a look to the future
- Suspension of Starship launches. The SpaceX team is likely to take a break to complete comprehensive ground tests.
- Redesign. The S35 and S36, which are at different stages of readiness, are likely to be seriously modified or disassembled altogether.
- Delays in other programs. In particular, the lunar landing under NASA’s Artemis program may be delayed if the Starship does not demonstrate reliable launches.
- The focus is on identifying resonance. Perhaps SpaceX will introduce active damping methods, change the length of pipelines, or even revise hot separation.
SpaceX has vast experience in rapidly updating its design based on lessons learned from failed launches. The company considers the loss of test samples an acceptable price for accelerated development. Therefore, many experts are not surprised that two consecutive launches have revealed weaknesses in the design. Similar lessons have helped SpaceX make the Falcon 9 one of the most reliable launch vehicles. Now a similar approach is being applied to Starship.
The Flight 8 crash showed that efforts to quickly address the shortcomings after the January disaster did not bring the desired result. The main problem remains the resonant vibration in the second stage fuel system, which leads to cascading damage. Despite the scale of this malfunction, it is not hopeless – similar situations have already occurred in the history of astronautics, when the rocket had to be significantly redesigned.
SpaceX will continue to improve the Starship, as it is a key component of the ambitious program of flights to the Moon and Mars. More time will likely have to be allocated to exploratory testing, as well as radical changes to the configuration of the engine compartment. Ultimately, each accident provides invaluable experience that allows us to create a more perfect system. So, although the Starship program is currently experiencing significant delays, its long-term goal of making spaceflight massive and reusable remains. And if the problem is successfully resolved, we will be able to witness breakthrough achievements in rocketry.
