​​What is a Space Pen?

The Space pen is a concept design pioneered by American Engineer Paul C. Fisher, he designed the space pen factoring gravity, atmospheric pressure and variance in temperature. 

Fisher developed the concept frustrated with leaking ball points for aeronautical applications and received no funding from NASA or any other government agency for its design, reeling from the controversy of 1965, it was not until 1967 that NASA after rigorous testing adopted Fishers Space Pen for astronauts who were part of Project Apollo. 400 Pens were purchased at a unit cost of 6$. 

Fishers space pen could write on almost any substance from butter to steel, in any temperature ranging between -30 to 250 degrees Fahrenheit, at any angle and used pressurized ink cartridges with a special kind of ink called as Thixotropic ink. A type of viscous ink that only flowed under stressful conditions perfect for aeronautical and astronomical applications. 

The body was constructed with tungsten carbide and high precision fitting ensured no leakage. It also employed a sliding float separating the ink from the pressurized gas. Nitrogen was the gas employed in the pressure chamber which ejected the ink at 45 psi. The design solved the problems of pressure, temperature and gravity and enabled it to last 3 times longer than a regular ball point pen. This unique design patent was filed on 19 May 1965.

Fishers Space Pen is employed even today but the 2 models produced in the days of early space missions were the AG7 Astronaut Pen, a retractable pen shaped like a ballpoint pen and a shorter version called as the Bullet Pen which had a cap.