----- Original Message -----
From: "David Weinshenker" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Thursday, October 30, 2003 11:29 AM
Subject: [ERPS] Re: Pens in Space
> What's wrong with conventional felt-tip pens ("Flair", "Le Pen", etc.?)
> for the application? They should be perfectly non-gravity-sensitive and
> non-particle-generating...
In Apollo days, the first objection would have been pressure sensitivity in
the low cabin pressure (IIRC, about 5 psi) as well as the effects of
outgassing carriers from the inks. Even the water based inks would tend to
dry in the tip, destroying the utility of the pen, in just minutes (maybe
seconds) as rapid low-pressure evaporation deposits ink solids in the fiber
material. Additionally, some inks have flammable carriers, which is a Very
Bad Thing in pure oxygen.
In today's spacecraft, most of which use a gas mix similar in pressure and
composition to air, there's less reason not to use these, though they're
still more sensitive to being left uncapped than a ball point. Hauling a
pen to orbit and then having to bring 3-4 spares because it quits working if
you leave the cap off for a few hours isn't sensible compared to taking a
pressurized or pump-operated ball point.
And water based (i.e. low/no odor or potentially toxic carrier fumes)
markers don't tend to write well on glossy surfaces or on some plastics --
ball points have trouble with plastics like polyethylene, too, but will
write on most glossy papers without the ink beading (as happens with water
based markers).
Really, the only solutions that work well for the environment are ball point
and pencils (or markers similar to pencils). And if you take pencils, you
have to be very careful to take *no* erasers; eraser dust is much more
annoying (and dangerous, in terms of breathing) than the traces of
graphite/clay mix from the pencil itself, and for most of us erasing a
mistake made in pencil is so ingrained a reflex that we might not realize
what we've done until after spreading rubber junk throughout the module.
NASA wasn't made up of a bunch of dopes in the 1960s -- they were addicted
to spending money, but they really did create more good than bad engineering
in the Apollo years.
--
I may be a scwewy wabbit, but I'm not going to Alcatwaz!
-- E. J. Fudd, 1954
Donald Qualls, aka The Silent Observer
Lathe Building Pages http://silent1.home.netcom.com/HomebuiltLathe.htm
Speedway 7x12 Lathe Pages http://silent1.home.netcom.com/my7x12.htm
Opinions expressed are my own -- take them for what they're worth
and don't expect them to be perfect.
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