Jan 13, 2012

Space pen | Zero gravity pen | Astronaut's pen AG7 - Fisher Space Pen Co.

Space pen or Zero Gravity pen or Astronaut's pen or Anti Gravity pen implies a ball point pen which can function without gravity.

Anti gravity pen was invented by Paul Fisher, who founded the Fisher Space Pen Company.
The specialities of this pen is it can write at any angle, in zero gravity, underwater, on oily and greasy surfaces and some more.Operating temperatures range from −30 to 250 °F (−35 to 120 °C). The pen has an estimated shelf life of 100 years.

Contrary to famous stories, the research for these pens were not funded or aided in anyway by NASA, but their testing for suitability for use in outer space was carried out by NASA before their official use in APOLLO mission. Fisher Space pens were used on Apollo 7 in 1968 two years of testing by NASA.

Some very interesting literature is available for background reading on Fisher company and Paul fisher. You can refer to [1] [2] and [3]. The NASA writing tool specification mentions AG7 'Astronauts pen' [4]. 

The Original or basic patent for AG7 space pen (zero gravity pen / anti gravity pen /astronaut's pen) is US3285228 which was filed on 19th may 1965.

If you are from India and looking to buy Fisher Pens online see my post here

The working of the space pen
Essentially the role of gravitational force in a normal ball point pen is to pull the ink down to the ball. This fucntion is performed by the pressurized gas and a movable float in the space pen. The pressurized gas pushes the float which in turn pushes the ink towards the ball.

As the force of the pressurized gas doesn't depend on the orientation of the pen (unlike gravity)
the pen can write at any angle even upside down.The ink is forced out by compressed nitrogen at a pressure of nearly 35 psi (240 kPa).

The ink is a special type of semisolid thixotropic ink which liquifies only when necessary thus avoiding leaking and lasting longer.

The ballpoint is made from tungsten carbide and is precisely fitted in order to avoid leaks. The thixotropic ink in the hermetically sealed and pressurized reservoir is claimed to write for three times longer than a standard ballpoint pen.


Paul fisher passed away at the age of 93 in 2006. As a tribute to his contribution i will be writing an inventor article on him soon, covering all his patents and inventions.

[1] http://www.spacepen.com/about-us.aspx
[2] http://articles.latimes.com/1997-02-24/business/fi-32017_1_space-pen
[3] http://www.hydeparkmedia.com/fisher.html
[4] http://www.thespacereview.com/archive/613d.pdf