Everything About Space Pens

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It takes a special pen to be used in space. For one thing, most ballpoint pens and all fountain pens use gravity assist to pull the ink down. Anyone who has tried to hold something against the wall and write on it has quickly found that they don’t get more than a few words before the pen runs dry. Furthermore, in the vacuum of space, the ink would evaporate and dry out and quit flowing. The ink will get too thick to flow if it gets too cold. If it gets too hot, then it will dry out and not flow. So, there are several reasons, ordinary pens can’t be used in space. So, let’s know “Everything about Space Pens”.

Everything about Space Pens

According to an urban legend, NASA spent millions of dollars designing pens to fly in space, while the Soviet Union simply equipped their cosmonauts with pencils. Like so many urban legends, though, this one is false. NASA purchased 400 of these pens for about $6 apiece. That’s a bit much for a pen, perhaps, but they are quite good pens. Eventually, NASA bought even more. The pens were used on Apollo missions, Skylab, and the Space Shuttle. And, eventually the Soviet Union began purchasing Fisher space pens for its cosmonauts. They are still used in space today.

Problem with Pencils

As it turns out, both NASA and the Soviet space agency realized that ordinary pens would never work in space. So, they gave the astronauts pencils. The problem, though, was that the pencil leads broke off and floated around in the space capsule, which could drift into an astronaut’s eye, risking injury. The astronaut could inhale the pencil lead. And worst of all, the pencil lead could find its way into a sensitive switch, interfering with the operation of the spacecraft during a critical moment. No spacecraft was lost due to a pencil lead, but NASA didn’t want to take the chance.

Also, ordinary pencils were made of wood, which was flammable in the pure oxygen atmosphere of the space capsule. Furthermore, astronauts had trouble holding the pencils and writing when wearing bulky space suit gloves. And, to make matters worse, the pencil with its sharp point floated around the capsule in the way, and also risking injury to the astronaut’s eyes.

NASA’s Special Pencil

The cosmonauts of Soviet Union used grease pencils to write in space. But, grease pencils can be messy, and the writing can smear and rub off. Instead of using grease pencils, NASA had special pencils created for the Gemini missions. The original Mercury missions were not designed for extravehicular activities (space walks) so the Mercury space suits were not as thick and bulky as the Gemini space suits, which were designed for exposure to the vacuum of space, since one of the goals of the Gemini project was to conduct extravehicular activities.

This required special pencils that were large enough for the astronaut to handle with heavy gloves on, and these pencils needed special housings that could be attached to the walls of the capsule so that they wouldn’t float around. An ordinary clip wouldn’t do because the astronauts would not be able to manage its operation with the gloves on. Those special pencils were very expensive, and NASA got a lot of bad public press attention over them.

The Invention of Space Pens

space pen-everything about space pen

But, all that attention brought the whole issue of writing in space to the attention of Paul C. Fisher. He realized that there ought to be a way of making a pen write in space. The solution was simple. Don’t use gravity to move the ink. Instead, he used a sealed ink cartridge with a pressurized gas chamber at the end instead of it being open to the atmosphere. The chamber is filled with nitrogen gas at a nominal pressure of 35 pounds per square inch. The gas in the pressurized chamber pushed on a plug at one end that in turn pushed the ink towards the ball point.

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Reportedly, his company spent nearly a million dollars developing the pen. But, the ink refills were of a size that they would fit into many other pens, effectively making them into “Space Pens,” too. Once Fisher was assured that his space pen met NASA’s requirements, he submitted it to the space agency for further assessment. NASA engineers tested the pen, and it passed all tests and proved to be safe, so 400 pens were purchased from Fisher, at a price of about $6 per pen.

 Challenges faced during development of Space Pen

One of the more difficult things in pen development, though, was the ink itself. It had to operate under all sorts of conditions that were not the normal environment for writing, not just with lack of gravity. Ordinary ink simply wouldn’t do. So, his company developed a type of thixotropic ink to fill the cartridge. This ink was practically a solid, more like a gel or a super viscous fluid than the normal liquid of most inks.

A thixotropic fluid is one that has a variable viscosity, with the viscosity becoming less under shear stress. The rolling ball at the writing end of the pen provided the shear stress as it moves past the end of the ink. That means the ink typically only flows if the ball is turning, as when the pen is used for writing.

But, this property means that it takes less ink to make a visible line, so the same volume of ink can be used to write far longer than a normal pen. The other advantage is that the ink is not as affected by temperature as most inks, and it doesn’t dry out. The ink can even be deposited on oily surfaces. Since the ink is not water soluble, the pen can even be used to write underwater (though you’d need special paper for that!).

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The pressurized gas chamber even allows the ink to flow against the pull of gravity. That means the space pen can be used here on Earth in the horizontal position or even upside down. That makes this a very versatile pen. It is no wonder that the pens are so popular. They now come in all shapes, sizes, and colors. Fisher now makes all sorts of specialized pens for firefighters, police, and even matte black pens for the military. In fact, they sell far more of the pens for use here on Earth than they do in space!


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