With the 50th anniversary of the Apollo 11 moon landing, an old internet trope has been making the rounds again. Essentially, it claims that while NASA spent millions of dollars of taxpayer money developing a pen that would write in zero gravity, their Soviet counterparts solved the problem by giving pencils to their cosmonauts. 

While this tale of government excess and failure to exercise common sense is comical, the actual history is more complicated. According to Scientific American magazine (1), both space programs initially used pencils, but tribological issues got in the way.

Basically, a pencil creates marks by depositing graphite on paper. However, not all the graphite that flakes off the tip is bonded to the paper. In normal gravity, these soot particles remain on the surface or fall to the floor. 

In zero gravity, however, graphite particles float around. Cleanliness is vital to the proper functioning of spacecraft, especially since graphite, as an electrical conductor, can potentially create electrical shorts in sensitive equipment. In addition, pencil tips break, creating a macroscopic floating hazard to the astronauts, especially if these sharp pieces get in the astronaut’s eyes or are accidentally inhaled. 

What is required, therefore, is a device that can mark a paper (or other) surface in zero gravity and not have any of the marking material become airborne.

The Fisher Pen Co. developed what is now commonly called the Space Pen using an ink cartridge pressurized with nitrogen to provide for ink flow regardless of the presence or direction of gravity. In addition to writing in any direction, the Space Pen writes in the vacuum of space and even under water. The company reportedly spent approximately $1 million to develop the pen and did so without using any taxpayer money. Pens using this basic design have been used by both the Russian and American space programs since 1967. 

Of course, the extreme environment of outer space requires some improvements to the ink as well. This is a tribological issue as well. Controlling the rheological properties of the ink is vital. The Space Pen ink is a semi-solid gel that liquefies when the tungsten carbide ball in the tip rotates. The gel is sufficiently viscous that the pen doesn’t leak when not in use and won’t freeze at temperatures as low as -45 C (-50 F) or liquefy when warmed to 205 C (400 F). 

The Space Pen is so successful that it remains in production, in many models, to this day. In fact, for as little as $50, you can purchase an actual Space Pen (2).

REFERENCES
1. Available here.
2. Available here.