The best things come in small packages (#2)
In part one of the series, we looked at how the ball plays a crucial role in the functioning of the ball point pen. In this post, we shall articulate how space pens work.
Unlike most ballpoint pens, the Fisher’s space pen* does not rely on gravity to get the ink flowing. Instead, the ingenuity lied in pressurizing the cartridge with nitrogen at 35 psi( 240 kpa )
This pressure pushes the ink towards the tungsten carbide ball at the pen’s tip.
How can it write in any orientation?
As the force of the pressurized gas doesn’t depend on the orientation of the pen (unlike gravity based ones ) the pen can write at any angle even upside down, in any fluid, adverse climatic conditions, and well, space!
The ink is a special type of semisolid thixotropic ink which liquefies only when necessary, thus avoiding leaking and lasting longer.
It’s a lot like ketchup where you go to pour your ketchup and nothing happens, but suddenly you are left with a large quantity of ketchup on your plate. Only upon the application of the force does the ketchup liquefy and at all other times it remains as thick gel.
Why is ketchup so hard to pour?
Another advantage of using pressurized nitrogen is that it prevents air from mixing with the ink so it cannot evaporate or oxidize,
Did NASA actually invest millions on developing the pen?
NASA invested millions (sometimes stated as billions) into developing a pen that would work in orbit. However, when the Russians went into space they just took pencils.
It’s a famous story that is mostly false.
Although Soviet cosmonauts did use pencils in space for a time, so did the Americans. However, it quickly became clear that pencils were a very bad idea since they had a habit of breaking and sending tiny eye-seeking fragments of pencil lead and wood bits into the air.
There were also some concerns over these fragments potentially damaging equipment, even perhaps causing a fire..
Hope you guys enjoyed this post. Have a great day!!
* Fischer was the guy who came up with the idea of a space pen and sold it to the government for $6.
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