basilton:

In the early years of space flight, both Russians and Americans used pencils in space. Unfortunately, pencil lead is made of graphite, a highly conductive material. Snapped graphite leads and particles in zero gravity are hugely problematic, as they will get sucked into the air ventilation or electronic equipment, easily causing shorts or fires in the pure oxygen environment of a capsule.

After the fire in Apollo 1 which killed all the astronauts on board, NASA required a writing instrument that wasn’t a fire hazard. Fisher spent over a million dollars (of his own money) creating a pressurized ball point pen, which NASA bought at $2.95 each. The Russian space program also switched over from pencils shortly after.

40 years later snide morons on the internet still snigger about it, because snide morons on the internet never know what they are talking about.

Source: yourresidentginger