PRESENTER: The space pen can
write in zero gravity, which is why astronauts have used it. It also writes underwater,
in extreme heat or cold, or when held upside down. All this is possible
due to the pen's ingenious design that
keeps ink flowing toward the tip no matter what. The space pen's ink is
pressurized with nitrogen. So unlike ordinary ballpoints,
it doesn't rely on gravity to flow toward the tip. Invented in 1966, the
pen first went into space with the Apollo 7 astronauts. The pen's writing point starts
out as a 3/10 of an inch long block of stainless steel. It passes through more than a
dozen machining operations that progressively shape a point
then bore a hole through the tip to form a pocket for
the carbide steel ball. That makes this a ball point. The last station
inserts the ball and curves the
edges of the pocket inward so that the
ball is locked in yet can rotate to spread ink. The replaceable ink cartridge,
called the "refill," begins as an empty brass tube. This assembly machine
inserts a white plastic ball into the back end then
pumps in half a gram of ink. The white ball is
called the "float." Its job is to follow
the ink down the tube, moving residual ink
forward toward the point. Next, the machine
inserts the writing point into the opposite
end of the tube, then it crimps the end
to ensure the writing point can't dislodge. Back to the other
end of the tube now, the machine applies
a bit of sealant, injects nitrogen to pressurize
the refill, then caps the tube with a hollow brass plug. Nitrogen is ideal for
pressurizing because it's an inert gas that doesn't
harm the refill tube or its contents. This demonstration shows
how the pressurized nitrogen forces the ink flow. After subjecting each and
every refill to a writing test and washing the surface to
remove traces of machine lubricant and other
residues, a printer applies the company
name and product information on the refill. Certain space pen
models have a cap that fits over the writing point. A feeder places a brass cap on
each poke of the cap assembly machine which then pushes
the cap into position to receive a clip. The clip is stamped
out of spring steel, a fairly flexible metal. It's chrome-plated for corrosion
resistance and aesthetics. The machine drives
the clip's teeth through the wall of
the cap then curls them back toward the
inside of the wall, locking the clip in position. To prepare the two-part
brass body of the pen, a feeder drops the
bottom part, called the "barrel," onto each poke
of the barrel assembly machine. To straighten the
writing end, the machine inserts a brass reinforcement
piece called the "nose tip." It then crimps the end, flaring
the nose tip inside the barrel, so that it becomes wider
than the barrel opening and, therefore, can't slip out. This model has a chrome-plated
brass body and clipless cap. To begin assembling the pen,
workers place the barrel in a foam holder,
insert a spring to keep the refill in position,
then a threaded connector made of brass. The barrel goes
through a machine which puts a silicone
rubber O ring on the top edge of the barrel. And now the final assembly. They place a refill
in the barrel, insert the connector into
the top half of the body, then, with an electric motor,
thread the parts together. After placing the cap open
side up in a foam holder, they insert the pen. The O ring holds
the cap in place. The original space pen,
still in production, has a push button on top to
push out the refill and another on the side to retract it. This demonstration pen
has a cutaway section to show the inner workings. All space pen models can write
underwater and in zero gravity. They also work in freezing cold,
intense heat, and upside down.
