Fisher Space Pen Refill Cartridge
The new visco-elastic ink, with a consistency similar to that of very thick rubber cement, flows as a result of the shearing action of the rolling ball in its socket. This shearing action liquifies the solid gel thixotropic ink, allowing the pen to write smoothly and dependably on most surfaces and even under water (although we would not reccomend that you take your bullet space pen down to 30 meters!).
Evaporation, wasted ink and back leakage are eliminated. Shelf-life is increased to an estimated 100 years.