From Wikipedia: "The wood pencil has been used for writing by NASA and Soviet space programs from the start. It is simple with no moving parts, except for the sharpener. However, wood, graphite, and rubber (in the eraser) are all combustible and create dust. Graphite, in particular, burns to produce dust that conducts electricity."
"The Fisher Space Pen was actually developed independently and privately in the 1960s, NASA later purchasing 400 of the pens at $6 each.[1] The Soviets followed as well." (https://en.wikipedia.org/wiki/Writing_in_space )