wrote:
I think I understand why objects heat up when going through the
atmosphere and therefore why re-entry vehicles need heat shielding. My
question is why we don't need heat shielding when launching. Aren't we
going through the same atmosphere?

1) Launchers often DO need heat shielding during launch. The nose of
the shuttle's external tank is darkened and scorched a bit by launch.

Notice how the nose of the ET is darkened here compared to the sides:
http://www.orbit6.com/et/img/etank2.jpg

But in this picture, the nose is the same color as the rest of the
tank:
http://www.orbit6.com/et/img/91etksc2.jpg

2) Yes, it's the same atmosphere, but the rocket is moving much slower
during launch than re-entry. During launch, rockets are generally
moving at only a couple thousand miles per hour before they're above
most of the atmosphere. During re-entry, they hit the atmosphere at
17500mph.

Mike Miller