>The heatshield held out for a much longer time, the asymmetric heating on the flaps was interesting. I had guessed that all four flaps would have equivalent heating based on an approach that was basically that side of the rocket perpendicular to the flow but it seems like that isn't the case. Still it seems like they are close to having something workable here.
Heat shielding didn't look relevant at this section of the flight at all. The booster didn't have any shielding.
The booster actually does have heat shielding behind the engine bells, to protect against aerodynamic heating on the return. In some of today's footage you can see it glowing yellow.
However, Raptor 3 is supposed to obviate the need for this shielding.
The booster doesn’t travel fast enough to need heat shielding ever.
It makes zero sense to use heat shielding behind the engine bells. Why? Think about it. If the booster renters the atmosphere engine bells first the engine bells would burn up BEFORE the air even touches the heat shield. If there are actually tiles there it’s just there to protect the booster from the heat of the exhaust.
> However, Raptor 3 is supposed to obviate the need for this shielding.
Not completely getting this. So there’s a case for the booster entering the atmosphere at orbital velocity engine bells first? I would think if they did this then THEY want the booster to burn up. Anything entering the atmosphere at that velocity needs to be made aerodynamically stable as it will be traveling faster then the speed of sound. This is what causes the heat. If you send something at the speed of sound engine bells first that’s not stable and is unlikely they will do that at all, with or without heat shielding.
I don’t think parent knows what he’s talking about.
> Where did it glow yellow? What time in the video?
This is a better view than the sibling comment linked. It's a greater close-up and you can clearly see the yellow glow behind the engine bells. This view is from Cosmic Perspective, a partner of Everyday Astronaut, whose video is linked:
In case you get confused due to lack of context, the booster shot is a replay. When Tim goes to split-screen view, the right-side image is a live view of the second stage ("Starship") as it re-enters from orbital speed. It is not a different angle on the booster that is shown on the left.
Later commentary explains that the heating behind the engine bells is due to atmospheric compression and SpaceX specifically orients the drop of the booster to focus heating in this spot.
You ought to do some basic research before making a post like this. Honestly might be the most baffling comment I've ever seen on HN---what kind of mindset does it take to have this kind of overriding confidence in one's own lay speculation?
The engine bells are made of different material than what's behind them (a material that has to directly withstand hot exhaust) and the aerodynamics of the ass end of the rocket are complex; some combination of these factors means this heating isn't an issue for the bells but is a concern for what's behind them. The booster does not re-enter from orbital velocity, but does come down engines first at supersonic speed. Stability in this orientation throughout the descent is a problem SpaceX solved with Falcon 9, and SH works the same way.
See the other reply to your comment for timestamped video of aerodynamic heating behind the engine bells.
Is it possible you're confusing the booster with the second stage (Starship)? They are not the same thing.
>You ought to do some basic research before making a post like this. Honestly might be the most baffling comment I've ever seen on HN---what kind of mindset does it take to have this kind of overriding confidence in one's own lay speculation?
Don't appreciate this at all. I can be wrong, but there's no need to make personal comments on my mindset.
Here's a timestamped link to Scott Manley's commentary video where he points out that the yellow glow at the bottom of the booster is the heat shielding behind the engines.
Heat shielding didn't look relevant at this section of the flight at all. The booster didn't have any shielding.