5 ms·

When people say something will "burn up on reentry", a phrase that I've heard almost all of my life but never really given much thought too, how burnt are we ta

When people say something will "burn up on reentry", a phrase that I've heard almost all of my life but never really given much thought too, how burnt are we talking? Surely it doesn't just completely atomize?

bipvanwinkle 5y ago
I’d love to know more about this too.
Lev1a 5y ago
I don't know specifically but as a layman I'd imagine the satellite breaking up into smaller and smaller pieces due to the rapid heating and the "wind resistance"(?) from making contact with the atmosphere at high speeds. I'd also imagine that at some point in this breaking-up-process the pieces are small enough to sublimate from the extreme heat, i.e. "burning up".
MPSimmons 5y ago
Do you remember, back when SpaceX used aluminum grid fins, when you'd see a Stage 1 re-entering, and you could watch the grid fins erode away in realtime video? Think of that, but for, well, everything.
sennight 5y ago
You know how racecars spectacularly fly to pieces when they crash? That is by design - as it rapidly sheds energy. Same thing applies to things that "burn up on reentry", so long as you prevent the thing from coming down as one solid lump of glowing hot metal - the surface area to mass ratio renders the fragments harmless. I wonder if anyone has ever tested the whole thing about field mice surviving a drop from any height due to their low terminal velocity... those bat bombs in WWII don't count.
mlindner 5y ago
Here's a video of a satellite (a very large one) reentering: https://www.youtube.com/watch?v=OhBw5yaR_SU https://www.youtube.com/watch?v=OhBw5yaR_SU And here's a timelapse in a hypersonic plasma test chamber: https://www.youtube.com/watch?v=q_AcG4ZQItg https://www.youtube.com/watch?v=q_AcG4ZQItg (Keep in mind the pieces that come off are still going to keep being heated even after they seperate.) It largely does atomize yes, depending on the material. Which is why they're designed out of materials that will do this.

bipvanwinkle 5y ago

I’d love to know more about this too.

Lev1a 5y ago

I don't know specifically but as a layman I'd imagine the satellite breaking up into smaller and smaller pieces due to the rapid heating and the "wind resistance"(?) from making contact with the atmosphere at high speeds. I'd also imagine that at some point in this breaking-up-process the pieces are small enough to sublimate from the extreme heat, i.e. "burning up".

MPSimmons 5y ago

Do you remember, back when SpaceX used aluminum grid fins, when you'd see a Stage 1 re-entering, and you could watch the grid fins erode away in realtime video? Think of that, but for, well, everything.

sennight 5y ago

You know how racecars spectacularly fly to pieces when they crash? That is by design - as it rapidly sheds energy. Same thing applies to things that "burn up on reentry", so long as you prevent the thing from coming down as one solid lump of glowing hot metal - the surface area to mass ratio renders the fragments harmless. I wonder if anyone has ever tested the whole thing about field mice surviving a drop from any height due to their low terminal velocity... those bat bombs in WWII don't count.

mlindner 5y ago

Here's a video of a satellite (a very large one) reentering: https://www.youtube.com/watch?v=OhBw5yaR_SU https://www.youtube.com/watch?v=OhBw5yaR_SU And here's a timelapse in a hypersonic plasma test chamber: https://www.youtube.com/watch?v=q_AcG4ZQItg https://www.youtube.com/watch?v=q_AcG4ZQItg (Keep in mind the pieces that come off are still going to keep being heated even after they seperate.) It largely does atomize yes, depending on the material. Which is why they're designed out of materials that will do this.