Editing Atmospheric entry (section)

====Carbon phenolic====
Carbon phenolic was originally developed as a rocket nozzle throat material (used in the [[Space Shuttle Solid Rocket Booster]]) and for reentry-vehicle nose tips.
The [[thermal conductivity]] of a particular TPS material is usually proportional to the material's density.<ref name="Di Benedetto">{{cite book|last1=Di Benedetto|first1=A.T.|last2=Nicolais|first2=L.|last3=Watanabe|first3=R.|title=Composite materials : proceedings of Symposium A4 on Composite Materials of the International Conference on Advanced Materials – ICAM 91, Strasbourg, France, 27–29 May 1991|date=1992|publisher=North-Holland|location=Amsterdam|isbn=978-0444893567|page=111}}</ref> Carbon phenolic is a very effective ablative material, but also has high density which is undesirable.

The NASA [[Galileo Probe]] used carbon phenolic for its TPS material.<ref name=HSAE>{{cite journal |last=Milos |first=Frank S. |journal=Journal of Spacecraft and Rockets |issn=1533-6794 |year=1997 |doi=10.2514/2.3293 |title=Galileo Probe Heat Shield Ablation Experiment |volume=34 |issue=6 |pages=705–713 |bibcode=1997JSpRo..34..705M |url=https://zenodo.org/record/1235941 }}
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If the heat flux experienced by an entry vehicle is insufficient to cause pyrolysis then the TPS material's conductivity could allow heat flux conduction into the TPS bondline material thus leading to TPS failure. Consequently, for entry trajectories causing lower heat flux, carbon phenolic is sometimes inappropriate and lower-density TPS materials such as the following examples can be better design choices: