SpaceX News

[ltgbrown]

It was a bit scary how many tiles came off the Starship. Hopefully they have a path ahead for dealing with that.

[mvanwink5]

It was a bit scary how many tiles came off the Starship. Hopefully they have a path ahead for dealing with that.

As I understand it, there is a procedure to test tiles in the weld sections of the Starship for adequate adhesion where pins for securing tiles are not applied. However, that tile adhesion test procedure was not performed on S25 that was launched during SFT-2, & that section of the thermal protection was where virtually all the tiles were lost. Still, it seemed to me that there were other tiles lost or damaged (seeming to have cracked), so IMO your concern is still warranted just not as bad as it looked.

[Skipjack]

With Starship using steel for the structure, I wonder how many tiles it can lose before catastrophic failure.

[KitemanSA]

With Starship using steel for the structure, I wonder how many tiles it can lose before catastrophic failure.

They have a blanket under the tiles. I’ve wondered if the blanket itself (or a thicker one) would suffice or if they could make do by adding spray cooling of the steel.

[Grumalg]

I remember back in the early days before starship was even built and tested, the plan then was to *not* use tiles. They said back then they were going to have many small holes and pump water spray through them to cool during rentry...

Never saw when they decided to go with tiles, but its probably an interesting story...

[Giorgio]

I remember back in the early days before starship was even built and tested, the plan then was to *not* use tiles. They said back then they were going to have many small holes and pump water spray through them to cool during rentry...

Never saw when they decided to go with tiles, but its probably an interesting story...

They decided to go with the tiles because overall the tiles are lighter than creating a second skin+water ballast+batteries and pumps and storage tanks.
I would bet that the unexpected issues they are having now with tiles is that the vibrations during take off are strong enough to actually fracture the lock pins of the tiles.
Of course (without any data from Spacex) mine is just a speculation based on personal past experiences, but if that was the case than they will need to rethink the lock system by either making much bigger pins, increasing the number of pins for tile, or by creating an interlock system among the tiles to spread the vibrations in a less destructive way.
The last system i mentioned, while more tricky to realize due to the thermal expansion movement of the tiles, is the more effective.

[mvanwink5]

Shock wave is gigantic. I wonder if there is reflection from the tower or the vertical tanks (dented again)? Of course tank walls are flexible so any reflected shock wave would be expected to effect the entire ship with any tile weakness being found such as the section weld lines where there are no pins.

[ladajo]

There was an issue with an actuator for one of the grid fins.

Where did you see this? I am still seeing a lot of speculation regarding the FTS triggers for both Booster and Starship. We may have to wait until SpaceX releases more information.
In any event, the launch through Hot Stage had to be a great source of data, in addition to the almost complete burn for Starship.
Spectacular! I am looking forward to the 3rd flight, hopefully soon.

[KitemanSA]

There was an issue with an actuator for one of the grid fins.

Where did you see this? I am still seeing a lot of speculation regarding the FTS triggers for both Booster and Starship. We may have to wait until SpaceX releases more information.
In any event, the launch through Hot Stage had to be a great source of data, in addition to the almost complete burn for Starship.
Spectacular! I am looking forward to the 3rd flight, hopefully soon.

Please note that his post was BEFORE the launch and simply reposted a widely reported fact. This was not a claim for why the unit exploded.

[Maui]

Specifically, it was the reason for the attempt being delayed by one day. They de-stacked and swapped out the actuator (actually, all 4 I think I read).

Not only not the cause of the explosion, but also the explosion probably made the issue irrelevant

[KitemanSA]

Specifically, it was the reason for the attempt being delayed by one day. They de-stacked and swapped out the actuator (actually, all 4 I think I read).

Not only not the cause of the explosion, but also the explosion probably made the issue irrelevant

Then again, the effectiveness of the grid fins may have contributed to the explosion by whipping the hull around fast enough to generate bubbles in the fuel lines. Or not!

[ladajo]

The altitude of the hot-staging should have greatly reduced any control authority for the grid fins. I saw a CFD effort showing the effect (impact) of the estimated, from flight videos and telemetry feed analysis, which shows significant fuel sloshing in both tanks.
My take here is SpaceX is doing some learning on the sequencing and timing of flight events for the stack, then booster and will likely be able to mitigate a lot of the drama for flight three now they have live data (way more than the internet has seen) to bounce against the sims they were running.
They did replace all four fin actuators pre-flight, one, then the other three right before. Speculation there related to extended weather exposure without operations or maintenance.
Looking ahead, I am also very interested to see what Starship Version 2 ends up looking like. We will see this soon as the Version 1 builds are finishing up now, and I think the first Version 2 will be Ship 32(? - I didn't check). The four most stated changes across the pundit spectrum are adding three more Vacuum Raptors giving a total of 6 x Vac and 3 x Sea Level, increased length (up to 10 meters), upgrades for main fuel tank bulkheads for capacity / weight / strength, and movement and shrinking of the forward fins closer to the nose and off axis to the leeward side.
While I would love to see another launch before the New Year, I think more likely it will be late January or even February. Got some static fires to get through once the flight two analysis and resulting flight 3 flight control adjustments are made. All this said, we still have no visibility on what happened to cause flight 2 Starship to execute an FTS RUD.

[Carl White]

I read somewhere that the grid fins actually could play a role in flipping the first stage, via interaction with the engine exhaust of Starship during the hot-staging.

[KitemanSA]

What Carl said.

[ladajo]

I had thought the same. However, after watching the Hot-Stage video several times, the separation seems fast enough that any possible control authority of the grid fins is negligible. Especially given when they are closest to the Starship plume, they are centered and positioned for least drag. It is possible they 'grabbed' a little bit of the plume while the two vehicles separated. Note, for them to get into the plume offset, as the Booster pivoted on axis, something else would have initiated the pivot, such as thrust vectoring of the center booster engines to commence the flip / boostback manuever.
More likely the Starship plume against the Hot-Stage cap had more effect. Much larger surface area and closer to plume impingement.
Meh, without detailed sensor data streams from SpaceX, or them releasing a report with analysis, we will likely never know.