One of the things that NASA had to figure out when it decided to put men on the moon in the Apollo era was how those astronauts would write in space. While the Russians went with the standard pencil and considered the problem solved, NASA wanted the astronauts to use a pen. The company who built the Space Pen is called Fisher Pen Company, and it celebrated the 50th anniversary of the Space Pen’s first flight in 1968 aboard the Apollo 7 mission last year.
Since that inaugural flight for the Space Pen, it has seen use on Space Shuttle missions and flights to the MIR Space Station, the pen has been on every single manned NASA spaceflight. As the pen has evolved over the years, different shapes and models have been produced for all sorts of uses. Despite different styles, the tech behind the pen has remained the same.
The core component that allows the pen to function in zero gravity is a pressurized ink cartridge, something that Paul Fisher, founder of the Fisher Pen Company, patented in 1966. The pressurized cartridge uses something called “thixotropic” ink. Matt Fisher, VP of Sales and Marketing for the company says that the ink is “close to a solid before being stirred.”
The stirring action to turn it into a liquid ink comes from the ball rolling in the point of the pen. That rollign action makes the ink very thin and allows it to flow in zero gravity. The primary motivation for developing the tech was to enable the pen to be used in space.
Over the years the pen has found use in a variety of environments other than space thanks to its ability to write upside down, in water, and on most surfaces. The ink can flow at a range of temperatures from -30F to over 250F. Despite the Russians favoring pencils, they have sent the space pens on flights with Cosmonauts.