clarification regarding the pen used by a astronauts

[arava prakash]

what is the principle behind the pen
1.which can be used to write in any angle?
2.used by astronauts in space (i.e in zero gravity)

 

[d3javu]

The ballpoint is made from tungsten carbide and is precisely fitted in order to avoid leaks. A sliding float separates the ink from the pressurized gas. The thixotropic ink in the hermetically sealed and pressurized reservoir is able to write for three times longer than a standard ballpoint pen. The pen can write at altitudes up to 12,500 feet (3800 m). The ink is forced out by compressed nitrogen at a pressure of nearly 35 psi (240 kPa). Operating temperatures range from −30 to 250 °F (−35 to 120 °C). The pen has an estimated shelf life of 100 years.

One of the first patents on space pen is US3285228, which was filed on 19 May 1965.[1] - Wikipedia

This video shows how they are made.