[Purdue77]

Can you imagine how hot it would get without 40,000 ft of atmosphere to help filter out the sunlight. Can you say flashburns.

[Calvin Locke]

I took a radiation module as a physics credit. I forget the number of mrem/hour at ~30k feet one receives through the aluminum.

Probably a crap shoot. Aluminum, post Apollo research, was found to easily give up neutrons from solar particle strikes, sending the heavier particles smashing through any strands of DNA they might encounter.