Confirmation that the problem wasn’t with SN4 itself, rather that as theorised it was leakage from the quick disconnect GSE fuel lines.
https://www.nasaspaceflight.com/2020...p-sn4-anomaly/
SpaceX set for a swift return to testing following Starship SN4 anomaly
Following the May 29 explosive failure of the Starship SN4 prototype during a Static Fire test, SpaceX workers have been quickly making repairs to its Boca Chica, Texas launch facility. Starship SN5 is expected to roll to the launch site in the coming days in preparation for testing to begin on June 10.
The anomaly totaled the existing test stand used to hold down the vehicle during the testing milestones. On June 3, a replacement launch stand was installed at the launch site. SpaceX had already been working on a new launch stand before the May 29 accident – a factor that accelerated the recovery process.
The new stand appears to be similar in design to the original Starship launch mount.
In the coming days, teams will continue to repair Ground Support Equipment (GSE) at the launch site. There was significant damage to GSE infrastructure due to the anomaly, but SpaceX will have the GSE repaired in time for testing to resume on June 10, per the latest notice of road closures.
While the Starship SN4 anomaly was dramatic, the required corrective action is not expected to be too complicated. Early indications were that an issue with the umbilical connections to the vehicle leaked significant quantities of propellant near the base of the vehicle. SpaceX CEO Elon Musk later confirmed to Reuters reporter Joey Roulette that the problem was related to the quick disconnect system.
It is understood that one of the test objectives of the May 29 static fire was to test disconnecting the umbilicals ahead of a planned 150-meter test flight scheduled for the following week. The umbilicals must be able to quickly detach when the launch vehicle leaves the pad. During the testing of the quick disconnects, the system malfunctioned – spilling large amounts of propellant. This could be seen during NASASpaceflight’s live stream of the test.
The propellant eventually ignited, leading to a large explosion. It is not entirely clear what the ignition source was, but a still frame from the NASASpaceflight broadcast shows that the ignition occurred near the base of the vehicle.
Notably, the structural integrity of Starship is not believed to be the cause of the accident. SpaceX has had issues with the prototypes collapsing under high pressure in the past. All of the previous full-scale prototypes failed cryogenic pressurization testing.
Including the May 29 test, SpaceX completed five static fires with Starship SN4.
No previous Starship had even gotten far enough to have an engine installed. The
Raptor engines performed well throughout testing, and the vehicle’s primary structure held strong.
If structural issues had been the cause of the recent anomaly, the flight-worthiness of SpaceX’s upcoming prototypes might have been invalidated. Starship SN5 is scheduled to roll to the launch pad on Monday, Starship SN6 is undergoing final assembly, and a Starship SN7 bulkhead has already been spotted. It is unlikely that the quick disconnect issue will require significant changes to these vehicles – avoiding a prolonged setback for SpaceX.
The lack of a significant design flaw with the vehicle will mean that the largest delay with SpaceX’s Starship testing flow will be the time required to repair the pad. The exact length of this process is not currently known, but Starship SN5 is expected to roll to the test stand within a few days.
Starship SN5 is now expected to be the first Starship to fly. Most likely, it will attempt the 150-meter hop test originally planned to occur with Starship SN4. However, SpaceX had also been planning to install three Raptor engines and a nosecone on Starship SN5 as opposed to the single-engine and no nosecone on SN4. It remains to be seen if SpaceX will proceed with these plans in the wake of the SN4 anomaly, or if Starship SN5 will end up looking similar to SN4.
Whatever the case, Starship SN5 is currently scheduled to undergo proof testing starting as early as June 10, with a static fire following later next week. SpaceX will likely conduct a few static fires before attempting a flight test.
Based on FCC filings, it is believed that SpaceX plans to conduct a 150-meter hop, followed by a three-kilometer hop, and then a 20-kilometer hop. Not all of these flight tests will be done with Starship SN5 – with the higher altitude tests likely slated for later Starship prototypes.......