At 06:35 PM 11/8/02, Erik Reuter wrote:
On Fri, Nov 08, 2002 at 06:19:37PM -0600, Julia Thompson wrote:> > However, there was at least one good reason that NASA chose not to > > use pencils: the wood and graphite shavings generated by sharpening > > a pencil would float in the air in microgravity, (1) being breathed > > in by the astronauts and (2) perhaps getting into the electronic > > equipment and causing short circuits (graphite being a conductor) or > > sparks, which would have been fatal in the pure oxygen atmosphere > > used prior to the Apollo 1 fire. > > OK, there's a way around *some* of those problems: use a mechanical > pencil. In my experience, the graphite in a mechanical pencil breaks off more often than in a wooden pencil (probably because it is thinner, maybe there is a thick graphite mechanical pencil, but I've never used one). Also, the graphite "rod" seems to break easily INSIDE the pencil when it experiences an impact. Then you have to feed a new graphite rod (or piece of rod) into the tube. Getting the new graphite rod to drop into the tube relies on gravity in all the mechanical pencils I have used. I suppose you could spin yourself in a circle and point the pencil outward while you clicked if you were in micro-gravity, but it would be a pain. And you risk having the fragment of graphite that broke fly out the end of the pencil as the new piece comes in.
The mechanical pencils I remember from back in the 60s used a fine screw inside the lead tube to advance the (0.9 mm or larger) lead as you rotated part of the barrel of the pencil. The only mechanical-pencil-type writing instruments I recall from back then (I was in high school when the first manned Moon landing occurred) which used gravity feed were lead holders used for drafting which used pieces of lead which were 2.0 mm thick and 4 inches long (sorry, Alberto, but that's what it says on the label on the package of lead): I don't recall seeing the Pentel 0.5 mm pencils on which you advanced the lead by pressing on the top of the pencil until I got into college in the early 70s, but of course some might have been available elsewhere before they got to Alabama.
Now, who recalls the drafting _pens_ of those days?
--Ronn! :)
I always knew that I would see the first man on the Moon.
I never dreamed that I would see the last.
--Dr. Jerry Pournelle
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