Fisher Space Pen Co.

In the quest for a perfect ink refill, Paul Fisher developed a prototype that used thixotropic ink and a cartridge pressurized with nitrogen, so that it didn't rely on gravity to make it work. The result was a pen that was dependable in freezing cold, desert heat, underwater, and — of course — outer space. Beginning with the October, 1968 Apollo 7 mission, NASA began using the Fisher AG-7 Space Pen and cartridge, cementing the pen’s legendary status.