The Russians used a pencil.

During the initial space flights, Nasa discovered that biro pens didn’t work under zero gravity conditions. To beat the problem, Nasa spent 6 years and $2 million in designing a pen for use in space. The pen would work under zero gravity conditions due to the pressurized ink inside, it would work under sub zero conditions, underwater, on glass and virtually any surface known to man. The Russians used a pencil.