As in the saying that the day got away from me, with a visit to an "urgent care" place - not an ER, but not a "put it off for later or next week" thing, either. Not Mrs. Graybeard or me, thankfully, but sucking up lots of time nonetheless. Dinner was about two hours later than usual and the evening still had things to do to help out.
So to put up something that people around here might want to read, as an anonymous commenter posted today at 2:23PM posted, today SpaceX uploaded a concise summary of their failure investigation of the RUD of Ship 33 which caused the end of Flight Test 7. Here are what seem to be the most important four paragraphs:
After vehicle separation, Starship's six second stage Raptor engines powered the vehicle along its expected trajectory. Approximately two minutes into its burn, a flash was observed in the aft section of the vehicle near one of the Raptor vacuum engines. This aft section, commonly referred to as the attic, is an unpressurized area between the bottom of the liquid oxygen tank and the aft heatshield. Sensors in the attic detected a pressure rise indicative of a leak after the flash was seen.
Roughly two minutes later, another flash was observed followed by sustained fires in the attic. These eventually caused all but one of Starship’s engines to execute controlled shut down sequences and ultimately led to a loss of communication with the ship. Telemetry from the vehicle was last received just over eight minutes and 20 seconds into flight.
Contact with Starship was lost prior to triggering any destruct rules for its Autonomous Flight Safety System, which was fully healthy when communication was lost. The vehicle was observed to break apart approximately three minutes after loss of contact during descent. Post-flight analysis indicates that the safety system did trigger autonomously, and breakup occurred within Flight Termination System expectations.
The most probable root cause for the loss of ship was identified as a harmonic response several times stronger in flight than had been seen during testing, which led to increased stress on hardware in the propulsion system. The subsequent propellant leaks exceeded the venting capability of the ship’s attic area and resulted in sustained fires.
Ship 33 from an onboard camera used to monitor it during the flight test. Image credit: SpaceX
If you follow any of the good sources working to keep us updated (e.g., Lab Padre, NASASpaceflight, and others) you will have seen that SpaceX has been working at a high pace to make this Wednesday's projected launch of Flight Test 8. The 60 second static fire mentioned in that linked post was part of testing out the ability to handle incidents like the ones that took out Ship 33. A check of the FAA site linked to in that post still shows the start of the launch window to be Wednesday afternoon at 2330 UTC or 5:30 PM CST.
It's hard to imagine how intense some of the forces produced during launch can be. It looks like the engineers have very good root cause analysis skills. A lot of companies could really learn from SpaceX. A lot of companies don't want to have to deal with the real root causes for a lot of their quality issues and won't go all of the way to address the real root cause.
ReplyDeleteCould this be the dreaded "POGO" effect? This ship was a bit longer than the earlier versions and would have a different frequency.
ReplyDeleteSolution will be, my guess, cutting BFH (big freaking holes) in the non-tiled side of said compartment, as there is no reason to have said compartment under pressure. Can't build up excess pressure in a hugely vented compartment, can we?
ReplyDeleteAnd it's really incredible that this was known basically before any of the pieces managed to make it back to the Earth's surface. This report is just confirmation of what Musk and SpaceX posted that day.
Starship and superheavy must be polluted with sensors, making it easy to extrapolate backwards sequence of events. Love those inside tank cameras, watching LOX swish around like water, pretty amazing.
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