As SpaceX Completes Second Starship WDR, FAA Conducts Safety Investigation Into Flight 3

by Adrian Beil

SpaceX is clearing the final milestones before launching the Starship vehicle for the fourth time. The FAA has completed its safety investigation into Flight 3 of Starship and has deemed it non-dangerous for the public. Additionally, the company successfully completed the second wet dress rehearsal (WDR) of the full stack consisting of Booster 11 and Ship 29, which went smoothly, according to the company.

The First WDR

After being stacked, SpaceX performed a partial tanking test with the stack on May 16. This was likely to verify the integrity of the vehicle and tank farm before moving to a higher propellant load.

The tank farm was heavily modified between flights, as SpaceX is moving away from the Starship-based vertical tanks and is transitioning to a more traditional tank farm setup using horizontal hotdog tanks. These extensive modifications necessitate a more careful approach to fueling the new stack, as SpaceX still needs to learn and verify the new capabilities of the tank farm.

For this initial test, no evacuation was scheduled, and the roadblock on Highway 4 was not moved further down the highway, confirming that no complete propellant load was planned. For high propellant load activities, an increased safety radius is enforced around the Starbase launch area due to the higher risk to health and safety.

A frosty Super Heavy tank during the WDR. (Credit: Mary / NSF)

A few days later, on May 20, a full evacuation of Boca Chica village was planned, as confirmed by NSF’s Mary (@bocachicagal). This indicated that the company was preparing for a full WDR of the flight stack. After the tank farm started up and all necessary pre-chilling of lines was conducted, SpaceX began fueling the stack. However, according to previous tests and observations, this test did not go as planned.

Typically, the company aborts WDRs around the T-10 second mark, which marks the start of the detonation suppression system (DSS). This system was never observed during the test. Furthermore, the tank load on the booster seemed much lower than observed on previous flights and expected for this test. While the company did confirm the test on X, it seemed that another test might be forthcoming.

The full water deluge system was also not tested during this event, which usually happens at the very end of detanking, confirming a successful WDR in previous attempts.

The Second WDR

A few days later, on May 28, the company repeated the test of the vehicles, scheduling another roadblock and evacuation of the village.

This time, the stack reached the expected fuel levels for flight, and both the DSS and water deluge system were tested. On X, the company confirmed the test, stating, “Starship and Super Heavy loaded with more than 10 million pounds of propellant in a rehearsal ahead of Flight 4. Launch is targeted as early as June 5, pending regulatory approval.”

The vehicle was successfully detanked, and the stack was unstacked just a day later for final preparations before launch. On the previous flight, there were ten days between the WDR and launch, so a potential launch window as early as Wednesday, June 5, seems feasible.

A capability observed during this test was a 30-minute hold close to T-0. Several indicators showed that the vehicle was below the T-1 minute mark before the hold occurred. At that point, the vehicle remained in a steady state for 30 minutes before the DSS was activated, and the depress vents concluded the test.

It is unclear if this capability is planned and also possible during flight, but it might hint that SpaceX currently has the capability to hold the vehicle for 30 minutes at the very end of the countdown. This is a capability that the company’s previous vehicle, Falcon 9, does not possess.

The FAA response to the mishap of Flight 3

In addition to hardware readiness, regulatory readiness remains an important item for Flight 4 of Starship. Since Starship triggered a mishap, based on FAA guidelines, a mishap investigation was initiated for Flight 3, grounding the vehicle until completion. The reasons for grounding the vehicle are defined for licenses under 14 CFR Part 450 of the FAA guidelines. One of the criteria is the “unplanned permanent loss of the vehicle,” which Flight 3 qualified for.

There are two ways to return to flight. Previously, all Starship mishaps were closed using Path One, which means the FAA accepts a SpaceX-led mishap investigation report, where the operator identifies corrective actions for the vehicle and implements them on future flights.

For this flight, SpaceX chose Path Two, which involves an FAA public safety determination. In this process, the FAA makes a safety determination based on all available information to see if the previous flight involved safety-critical system failures. If successful, a return to flight can be conducted even without the closure of the mishap report.

In a statement to NSF, the FAA reported: “After a comprehensive review, the FAA determined no public safety issues were involved in the anomaly that occurred during the SpaceX Starship OFT-3 launch on March 14.

This public safety determination means the Starship vehicle may return to flight operations while the overall investigation remains open, provided all other license requirements are met. SpaceX has not yet received FAA license authorization for the next Starship launch.”

This likely means that SpaceX has not fully identified the cause of the mishap yet, and a full mishap report would delay the return to operations further.  The launch license modifcation is ongoing.

This modification will update license VOL 23-129, which authorizes the Starship Super Heavy vehicle flights. It is unclear if SpaceX will apply for only one or multiple flights under this license modification.

The road forward for flight 4

With the regulatory chapter closing, SpaceX must now perform the final work on both vehicles. This will most likely include a flight readiness and launch readiness review in the upcoming days, as well as closing the heat shield on Ship 29 and conducting final inspections on both vehicles.

The mostly complete heatshield of Ship 29 during inspections. (Credit: NSF / Sean Doherty)

After destacking, a few final panel gaps can be closed on the heat shield of Ship 29. Elon Musk identified the heat shield as a critical item on X for the future, and proving its function will be necessary to support missions for NASA HLS and demonstrate the full capabilities of the Starship system.

In an update on its website, SpaceX confirmed details about the heat shield and reentry aspects of the past flight.

“Starship went on to experience its first ever reentry from space, providing valuable data on heating and vehicle control during hypersonic reentry. The lack of attitude control resulted in an off-nominal entry, with the ship seeing much larger than anticipated heating on both protected and unprotected areas. High-definition live views of entry and a considerable amount of telemetry were successfully transmitted in real time by Starlink terminals operating on Starship.”

The loss of attitude control most likely resulted from a filter blockage in the attitude control system, which prevented the vehicle from orienting itself optimally in space. This is an issue SpaceX aims to address on this flight with the addition of more control redundancy for Flight 4 and upgraded hardware to resist blockages.

After the vehicles are closed out, the final step will be the installation and arming of the flight safety system (FSS), which consists of detonation charges on both Booster 11 and Ship 29. The charges were delivered a few weeks ago to the explosive bunker near the launch site and are typically installed in a multi-hour operation on both vehicles.

This installation requires the vehicle to be destacked, as the access point for the Ship’s FSS is not reachable from the ground when the stack is fully assembled.

Installation of the FTS began on Thursday, with the aim of arming the system ahead of restacking for launch day.

Once all these steps are completed, SpaceX will attempt to launch Starship as soon as June 5. The launch window opens at 7 AM CT. SpaceX has not disclosed the duration of the window.

(Feature Image: Starship Flight 4 Full Stack. By NSF/Mary (@bocachicagal))

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