How is plasma generated during spacecraft reentry?

[Swankie]

How exactly is plasma generated when space vehicles reenter Earth's atmosphere? How do the ions show up? I get how the air drag creates the initial heat, but from there I do not know. Have been searching the net for about 30min and came up with nada.

 

[boneh3ad]

When you get that hot, diatomic gases like oxygen and nitrogen begin to dissociate and you end up with with a bunch of ions floating around.

 

[Swankie]

Can someone confirm this? I was under the impression that the pressure, not the heat was the initiator

 

[boneh3ad]

You need energy for a gas to ionize. Pressure itself doesn't provide that sort of energy. However, the extreme compression that exists near the nose (and a few other areas) of hypersonic vehicles causes the gas to heat up and the heat leads to ionization. It is true that it gets that hot as a result of pressure changes, but it is the heat itself that causes ionization.

 

[Swankie]

Awesome, thanks for the clarification!