It's *not possible* to make a shield. The cosmic radiation that reaches that altitude is highly energetic and highly penetrating—enough so to go through 3 meter

It's *not possible* to make a shield. The cosmic radiation that reaches that altitude is highly energetic and highly penetrating—enough so to go through 3 meters of water—and would be completely unaffected by lead sheets. Any easily-shielded types of cosmic radiation have already been blocked by the atmosphere.