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I am just wondering are there any reasonable physics arguments behind difficulty making pen for no gravity conditions. My thoughts are that there are many ways to make it working as:

  • Pressurized cartridges
  • Using capillary forces
  • Using static electrical forces
  • Magnetic inks
  • etc?

I have understood that regular pencil is cheaper, but it has its own disadvantages as: breaking, need for sharpening, etc.

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  • $\begingroup$ There are no significant difficulties behind making pens for space. Fisher simply seized the craze of the day when they created their "space pen", which uses a pressurized cartridge and works just fine in space as well as under more general conditions in gravity. Unlike many other ballpoint pens it is said to write upside down just fine. I never had one, so I can't confirm just how much better it is. The main problem with pencils is the need for sharpening and that the material breaks up in small pieces. In space you are going to inhale that debris. Do you really want that? $\endgroup$ – CuriousOne Jun 12 '15 at 18:59
  • $\begingroup$ @CuriousOne I believe the main concern with pencils is that the graphite dust is conductive and can short out electronics over time. Before the space pen, the Russians used grease pencils to avoid the problem. $\endgroup$ – Rick Sep 28 '15 at 14:37
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I believe although there were no large physics hurtles to overcome in developing the space pen, all of the pens that were currently on the market at the time were highly unreliable without gravity assisting them, and were thus unacceptable for use in space. Additionally, pencils produced graphite dust which in space will float around until it lands somewhere. As graphite is conductive, over time a graphite deposit might build up enough to short out components. The Russian solution was actually to use grease pencils, but those have the tendency to smear so they too bought the "space pen" once it had been developed.

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