I took it to be glare. A fire would be yellowish, per the fires in the engine bay on the first flight.
Yes.
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SpaceX Starship - Integrated Flight Test #2 - Starbase TX - Including Post Launch Dissection
- Thread starter Grendal
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Humm, assuming that was commanded and not an asymmetric exhaust induced mechanical failure, does it seem like an effort to present the least crossection to the flow?
Yeah maybe so.
If we call that fin the "top" one, the side fin (pointing at the camera), is harder to make out, but I think I see the edge line of it, and it seems like it does NOT rotate... but hard to tell for sure.
(I just realized X.com allows you to play videos at 0.25x speed.... I'm pretty sure that side fin doesn't rotate...)
I don't think so. I've been watching it over and over. What I'm seeing now is a counterclockwise tilt to 30-45 degrees at the moment of staging. Either that's the exhaust damaging the grid vane or the grid vane being used to impart rotation. I continue to assume the latter because I can't see another reason for the booster to turn like that. If the engines were gimballing, then the bottom of the rocket would move out of line with the stack. Instead, the top moves out. I thought that perhaps the turn could be coming from asymmetrical venting from the interstage, but that wouldn't make much sense because the interstage would want to rotate instantly while the video shows a brief pause between separation and rotation.
In fact, the interstage is designed to dump exhaust right onto the grid fins. It sure looks intentional to me.
I tried watching the grid fin after staging, but the video is so dark that I can't tell if it moved back.
I'm just happy that I'm not hallucinating the movement.
30 would be my expected max for through fin flow. More than 45 and it seems like the opposite force direction would be imparted (if flow goes around fin)
Whether imparted by thruster, grid, or engine the booster will rotate around the center of mass which is much closer to the bottom than center due to engines, LOX, and thrust puck.
Plus, there is a lot of original velocity which skews observation.
The hot ring has openings at the 6 interstructure load points defined by the three clamps and halfway points. Alignment to grid fins is a side-effect as the phasing was set pre-hot-ring. The photo shows the ship offset as it is rotated into place by the chopsticks.
Yes, but if the engines gimbaled (which it doesn't look like they do, compared to Starship), their position close to the center of mass would produce more translation than rotation. I just don't see gimbaled engines producing that much rotation.
Ah, good point. I guess I'll just have to claim "fortunate coincidence", and continue to believe in grid fin turning via Starship exhaust.
Time will tell. My batting average with pet theories is around 0.100, so I won't be surprised to be wrong again.
Translation is forward velocity though, off axis thrust is rotation. Starship flip is largely gimbal induced.
I think lower center of mass does reduce the torque though. Top thrusters or fins would have an advantage in that respect, but in terms of total force, do engines win?
Sorry doubters, Starship actually had a remarkably successful flight
On just its second flight, Starship now is arguably as successful as NASA's SLS rocket.
arstechnica.com
This was included in one of Eric's comments to his article in response to the inevitable Musk-isn't-important comments. I do not want to derail the topic of this thread, but I did think this video was interesting.
Up above where it is in near vacuum at 68 km altitude, how will the grid fins have any effect ?
They're in the flow of Starship's exhaust at very close range. That exhaust caused a 500 ton booster to decelerate at roughly 0.7g for the time it was exposed to the exhaust, so there's some serious energy there.
Everyday Astronaut shots of the launch. My favorites are actually the ones that keep the ground in view. It's great seeing the closeup of the rocket body, but I have the strongest emotional reaction to seeing a rocket physically transition from being on the ground to being in space. If you've never seen a rocket launch in person, I highly recommend it.
64 m^2 of cross-section at sub 2 m distance is a bit different than the grid fin area vs plume column though...
Regarding gimballing, check the engine appearance during the flip. Stays fairly consistent until ? degrees into the flip which alignes with my preconceived notion of what engines tilting on a tiling body looks like
They're out because they can't be stowed. They don't cause a lot of drag, but stowing them would add weight and complexity. It's doubly difficult because Starship's booster grid fins are made of steel, not titanium. So if they wanted to raise and lower them, they'd need a pretty hefty mechanism, or they could reduce the weight and make them of titanium, which would be more expensive.
It may be that in the future, when SpaceX is optimizing Starship, they'll figure out the perfect balance of factors and go back to stowable titanium grid fins. Given that they know they're going to be destroying vehicles during testing, they just want vehicles that they can fly as cheaply and as quickly as possible. That means stainless steel, heat tiles, and fixed steel grid fins.
SpaceX doesn't want to add in all the mechanisms (more mass) needed for "fin deployment." They probably did the math and figured the weight gain versus aero loss was not worth it.
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