The pen writes upside down in extreme temperatures of -35C to 120C and comes with an unconditional lifelong guarantee. It was developed by Paul C. Fisher to substitute pencils, which write well in zero gravity but have as a disadvantage that the wood shavings, graphite dust or broken tips when floating about can pose a danger to electronics on board or may get into the crew’s eyes or be inhaled.
The Fisher Space Pen is a gas-charged ball point pen, which does not release any unwanted material. It is very robust and it works under all daily and not so daily conditions, such as zero gravity, vacuum and extreme temperatures. Its thixotropic ink and vent-free cartridge release no significant vapour at prevailing temperatures and at low pressures. The ink is forced out by compressed nitrogen at a pressure of nearly 240 kPa and keeps functioning at high altitudes. The pen however is more expensive than the pencils that were used before, but it has been used by both NASA and Soviet/Russian astronauts on numerous Apollo, Shuttle, Mir and ISS missions.
This blog post is part of a series of 'Man on the Moon' articles to honour the 50th anniversary of the Apollo 11 moon landing.