The
Fisher Space Pen was designed by
Paul C. Fisher for the
Apollo Program. Due to the hostile space environment, there were
strict
design requirements for the pen; it should
be able to write in a
vacuum, in the absence of
gravity and at
temperatures varying from -120 °C to 150 °C. Fisher had worked on a pen
design with a pressurized ink cartridge. This design was perfected in
1966, and in October 1968 the first Space Pen was used in the
Apollo
7 mission.
The ink of the Space Pen is fed to the ball point by pressurized
nitrogen, and thus can be used to write upside down and in a
vacuum. Due to the thixotropic behavior of the ink it remains
highly viscous and won't leak when the pen is not in use. When the ink
is put in motion by the ball point, its viscosity will drop so that
it starts flowing. The composition of the ink allows for writing on
a wide array of surfaces, under water, and also at extreme
temperatures.
There is a great urban legend regarding the design of the space
pen:
When NASA started the space program in the 1960's, they
were faced with the problem of writing in space. NASA spared costs
nor efforts design a pen that would perform in a vacuum, and in the
absence of gravity. Fortunately, the resulting Space Pen was a true
marvel of engineering that proved its worth in the early space
missions. The enthusiastic NASA engineers showed off the Space Pen to a
group of Soviet-engineers working for the Russian space program, and
asked them how they had solved the problem of writing in space.
"We use pencils", was their reply.
Although there is a valid lesson to be learned from this story
(Keep It Simple, Stupid!), it is merely an urban legend.
Prior to the Apollo 7 mission, both Russian Cosmonauts and
American Astronauts were relying on pencils for writing in
space. However, sometimes the pencil leads would break and go on a
free flight in the space capsule. The lead tips could float into an eye
or nose, or even into electrical devices causing a short circuit.
Furthermore, the wood and lead of the pencils could burn rapidly in a
pure oxygen environment. Because of a fire in Apollo 1 (resulting in
the death of three astronauts), NASA required a writing instrument that
would not burn in a 100% oxygen atmosphere, and would operate in space
conditions.
Sources:
(urban legend)
http://www.spacepen.com/
http://www.snopes.com/business/genius/spacepen.htm