More accurate than a mood ring—but every bit as colorful—pressure-sensitive paint (PSP) can tell engineers how a plane will fare under the extreme conditions it encounters in flight. The paint itself glows a faint red when it's put under blue or ultraviolet light. But that blush dims as a surface is exposed to more oxygen, which happens when atmospheric pressure increases. Specialized cameras pick up variations in the faint glow and feed the data to a computer, which analyzes it and spews out a rainbow of information on how well planes hold up under pressure.

Model jet fighters and even space shuttle prototypes have been painted with this stuff and tested in wind tunnels in an effort to make them fly better.

Slide Show: Pressure-Sensitive Paint Reveals Flight Physics