Well at least it’s not any GSE on fire, so that’s good news.
A bit surprised that there does not appear to be any effort made to putting it out.
A bit surprised that there does not appear to be any effort made to putting it out.
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I saw your earlier post about that. Still surprised by that strategy given the relatively low amount of vegetation present in the area but perhaps the location of the fire was too far away from the road to get access to. I do know what a “backfire” is and maybe that is the approach being used to control the fire. Currently NSF livestream isn’t showing anything burning.
SpaceX is certainly having some fire control issues during vehicle testing. A booster spin prime test resulted in a conflagration directly under the vehicle. Then the first 6-engine static fire of a Starship caused a brushfire. It seems that more attention needs to be paid to understanding and managing ignition sources during testing. At least no one has been injured and as far as we know no major damage has occurred to the vehicles or the GSE.
It does seem to indicate they are producing some amount of airborne heated debris which needs addressed. The important stuff is surrounded by non-burnables, but kicked up heated materials bypasses those protections. Maybe more Martinite fracturing issues?
This grass fire was in the same location as a previous test and did not pose a threat to the infractructure. It was bordered by water/ salt flats and then the road, so low risk of damage. Backburn got it over with sooner.
After the booster spin test unintended ignition, they added methane vent lines from the booster engines to the OLM to prevent buildup.
The rocket structure also flexes with engine force, along with normal cryo induced shrinkage. Losing just a few in isolated areas can get chalked up to process variation.
I suppose the ignition "thump" may give the stack a decent kick in the pants... even if it's at partial throttle.
Anybody have idea if the engines are throttled at all during startup, and if so what that level may be?
Depends which time frame you define startup.
From the Tim Dodd interview, it's a delicate balancing act to bring up the independent fuel and oxidizer pumps (esp since they cross feed each other). So there is a ramp there.
Once up to operating state, control is easier and I don't think there is a need to be at lower power before going to 100%. In 2019, the outer boost engines were going to be non-throttlable, but that might have changed with V2.
Here is a side-by-side comparison photo showing where the tiles were lost. Mostly near the base. Given that a full stack launch will have the ship much higher off the ground, and of course the ship engines won’t be active at launch, that may mitigate tile loss at launch.
But if it cannot stay glued at this level of vibration, how is it going to stay on during the extremely fiery reentry at 10k miles per hour. Remember they are not planning to have a re-entry burn to slow down before hitting the atmosphere, but hoping to slow down just using the flaps. (that is my understanding). That means it is going to hit the atmosphere at a speed much-much higher than the first stage.
With the understanding that I am definitely not an aerospace engineer:
During re-entry, atmospheric drag and tile temperatures build up gradually. There are gaps between the tiles, on purpose, because as the tiles heat up they expand so they fit together much tighter (SpaceX has data on that from subjecting tiles to high heat and pressure in their ground-based test equipment). Also, the aerodynamic forces on the vehicle during re-entry are very different than what it experiences during a static fire; during re-entry many (though not all) of the tiles are going to be forced onto their mounting pins.
So I would not come to any conclusions about how tiles might behave during re-entry based on how they behave during a static fire.
Of course SpaceX is not expecting the first Starship re-entry to go flawlessly; Elon has said it is unlikely to reach the ocean surface intact. It is going to take many re-entry attempts from orbital velocity for SpaceX to figure out how to land the vehicle and then re-use it. Just as it took many attempts to successfully land and reuse an F9 booster, which basically the entire aerospace industry said was impossible. I’m not hearing that industry make many such statements about Starship, at least not publicly.
During re-entry, atmospheric drag and tile temperatures build up gradually. There are gaps between the tiles, on purpose, because as the tiles heat up they expand so they fit together much tighter (SpaceX has data on that from subjecting tiles to high heat and pressure in their ground-based test equipment). Also, the aerodynamic forces on the vehicle during re-entry are very different than what it experiences during a static fire; during re-entry many (though not all) of the tiles are going to be forced onto their mounting pins.
So I would not come to any conclusions about how tiles might behave during re-entry based on how they behave during a static fire.
Of course SpaceX is not expecting the first Starship re-entry to go flawlessly; Elon has said it is unlikely to reach the ocean surface intact. It is going to take many re-entry attempts from orbital velocity for SpaceX to figure out how to land the vehicle and then re-use it. Just as it took many attempts to successfully land and reuse an F9 booster, which basically the entire aerospace industry said was impossible. I’m not hearing that industry make many such statements about Starship, at least not publicly.
Flaps are for attitude control, braking is via vehicle crossection. On Tim Dodd tour interview, Elon mentioned they could go smaller in flaps area and possibly eliminate one set.
Yesterday there was a multi-engine spin prime test of B7. Speculation that a major static fire is happening soon.
Some analysts think all 33 engines were spin primed during that test, sequentially in groups.
The video in this tweet is slowed down to frame-by-frame to visualize it better.
petit_bateau
Active Member
For sure; the potential interactions between all those engines must be extremely complex.
petit_bateau
Active Member
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