Why don't astronauts' vessels burn up while re-entering the atmosphere?

Currently, the astronauts and cosmonauts return to Earth in a Soyuz capsule. The Soyuz capsule has a curved ablative heat shield that is used to prevent heat from building up and penetrating the crew cabin.

As the capsule plummets through the atmosphere it slams into molecules of air. These bounce off of the capsule and in turn slam into the air molecules that were behind them. This creates a shockwave in front of the vehicle. The greatest temperature is at the shockwave, so forming the shockwave farther from the vehicle surface reduces the amount of heating the vehicle experiences. This displacement is related to the shape of the capsule and explains the curvature.

Some heat still makes it to the vehicle surface, and that’s where the ablative heat shield comes into play. As the outer molecules of the heat shield absorb heat, they reach a point where they vaporize and leave the surface of the vehicle. When they do this, they carry away the heat they have absorbed. This phenomenon is called pyrolysis. The next layer then gets hotter and hotter until it vaporizes and takes its heat away. Eventually, the vehicle has slowed to the point where heat is no longer significant and what is left of the outer surface will be relatively cool.

So, the idea is to create a heat shield that has the right curvature, ablative properties, and thickness such that significant heat never makes it to the crew compartment or vital equipment.

This information was taken from Quora. Click here to view the original post.

Now you know that our astronauts are safe while entering the atmosphere. Do you think it's a frightening experience for them?

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What are your thoughts on this subject?
John Sharp
Great information you can learn something new each day thanks.
Mar 30, 2020 7:27AM
Darlene Davidson
The last paragraph says it all.
Nov 26, 2019 7:26PM
Jim Adams
Big long narrative just to say heat shield
Nov 18, 2019 4:25PM
hector tubens
Good information.
Jul 28, 2019 8:53PM
Of course the Columbia Space Shuttle crash in 2003 upon re-entry made it obvious how important a complete heat sheild is.
Mar 23, 2019 4:23PM
Michael Hamilton
Good information.
Mar 6, 2019 9:24PM
awmcnair......Al Mac
I always wanted to know this; thanks
Jan 31, 2019 9:52AM
Gerald Woerner
Hadn't heard of pyrolysis before. Good information
Aug 16, 2018 11:19AM
Frances Bell
Very good info
Aug 14, 2018 7:02PM

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