Slashdot Mirror
Writing in Space with a Cheap Ballpoint Pen
Roland Piquepaille writes "Some days bring big surprises. Like many people, I always believed that it was impossible to write in space with ordinary pens because ink would not flow. So imagine my astonishment when I read Pedro Duque's diary from space this morning. Pedro Duque is an astronaut since 1992. Now, he's on board of the International Space Station (ISS) since October 18, 2003. And he's writing -- from space -- with a cheap ballpoint pen, like Russians apparently always did: 'So I also took one of our ballpoint pens, courtesy of the European Space Agency (just in case Russian ballpoint pens are special), and here I am, it doesn't stop working and it doesn't "spit" or anything.' Isn't it amazing? This summary contains more details and a photograph of Pedro Duque on board ISS." Note that NASA didn't go crazy developing a pen for space. Surface tension is the important factor for all pens, not gravity.
I think lack of gravity matters. In your upside down pen, gravity will pull the ink away from the ball.
It's the surface tension propteries of the ink, commonly known as capillary action.
We must be alert to the danger that public policy could become captive to a scientific-technological elite. - Eisenhower
Problem with a pencil is the graphite dust. Normal gravity, graphite dust isn't an issue, it gets mostly on the paper, you don't worry about that. Now, in space, that graphite dust lingers, gets into things, makes the environment not as friendly to be in as it could be. With a pen, this is much less of an issue, as the physics of writing are a lot different.
Marxism is the opiate of dumbasses
The reason for using pressure in pens, it seems, is that surface tension alone may not be enough to pull a long column of ink through a narrow tube. If there is a little bubble in the column of ink, the surface tension is broken, and there is no way to pull ink past the bubble.
The problem of a bubble in the column of ink happens on land, too, not just in space. People deal with it by just throwing the pen away. Since cheap pens cost less than 15 cents, someone may develop the habit of throwing away pens without noticing what he is doing. If a bubble develops, it is usually after the pen has had considerable use, so there is little complaint.
In situations of varying temperature and outside air pressure, unpressurized pens may develop a bubble more easily. Pressurized ink cartridges are a little more reliable, and cost the manufacturer only a little more.
Because gravity is still in action on the ink when the pen is horizontal, at a guess. Writing with the pen held horizontally isn't the same as writing in microgravity - in microgravity the stickiness of the ink is more than capable of pulling more ink towards the ball as it writes, whereas with the pen held horizontally in normal G it still has to pull ink "uphill" against gravity towards the top of the ball.
It'a another example of how nearly impossible it is to extrapolate what happens in space or on the Moon from our experiences on Earth - for more examples, check out Bad Astronomy on the Apollo "Hoax"