Con la caidita de Blogalia se me fue al carajo un comentario. Lo repito, más o menos:
Para regocijo de profes y alumnos, cortesía de SPACE.COM tenemos una unidad didáctica para hacer prácticas con el astropen y compararlo con los bolis mundanos. Leemos ahí (http://www.space.com/teachspace/module_astronaut_0900/pen_teachpg_0900.html):
Ballpoints and many other pens rely partially on gravity. Ink flows slowly down the barrel to a tiny ball in the tip. As the ball rolls, it transfers ink onto the paper. Capillary action - the attraction of a liquid to a surface like the pen's barrel or a sheet of paper - helps pull the ink onto the paper.
When inverted, ballpoints will deposit the ink that's clinging near the tip. But soon, the ink responds to gravity's pull - it flows back down the barrel and the pen no longer writes. Factors such as the stickiness of the ink, the amount of ink in the barrel, the width of the barrel and the width of the ballpoint affect writing time.
Roller balls and felt-tip pens rely less on gravity. Inside the barrel of these pens is a fibrous core. Capillary action pulls the thin ink through the fibers.
In orbit, the downward pull of gravity is not exerted. Pen inks that rely on gravity won't flow, no matter what position they're in. Today, all U.S. astronauts use the failsafe Fisher Space Pen. The barrel of the pen is highly pressurized; that pressure pushes ink toward the pen's tip. The Russian space program found a different solution to the problem - pencils!
This activity is a good chance to discuss scientific testing. The tricky part here is that two variables measure an inverted pen's effectiveness: the amount of time it keeps writing and the distance (number of lines) it writes. By making each line last for three seconds, we controlled the variable of time so we could evaluate the pens in terms of number of lines drawn. Time and distance are both dependent variables - factors that change depending on the independent variable, or the pen type.
Spaceships in orbit experience microgravity - a trace level of gravity that has little effect. Contrary to popular belief, the lack of gravity is not because the spacecraft is too far from Earth to feel its pull. Rather, it's because orbiting spacecraft are in a constant state of free fall - the shuttle's velocity balances the Earth's downward pull, so it continually "falls" around Earth. Microgravity exists within a free falling object.
En ASTROPEN (www.astropen.com) tienen toda la información sobre los bolis de Fischer, todos los modelos, testimonios agradecidos de los usuarios y etcétera etcétera (hasta unos videoclips mostrando en las extremas condiciones en que funcionan). Ah... y también una sección de FAQ, o sea PUF (preguntas usualmente formuladas) en la que leemos:
Q: During the heat of the space race in the 1960s, the U.S. National Aeronautics and Space Administration (NASA) decided it needed a ball point pen to write in the zero gravity confines of its space capsules. After considerable research and development, the Astronaut Pen was developed at a cost of about million US dollars! The pen worked and also enjoyed some modest success as a novelty item back here on Earth. he Soviet Union, faced with the same problem, used a pencil.
A: I've been forwarded this tidbit for years. This is not a factual story and has never been published. Whomever created this didn't understand that NASA didn't create the space pen, it was Mr. Fisher. It was NOT NASA that invested 1.5MM in the space pen, it was Mr. Fisher at ZERO cost to the American taxpayer or consumer. Also, pencil lead, breaking off in a zero-gravity environment could be harmful if ingested, and would be be detrimental if the broken lead became lodged inside the Shuttle's computer equipment. The graphite inside a pencil can be conductive with electricity, which is not good inside a computer system.
This story always makes the USA, NASA and Mr. Fisher look stupid while the Russians are so ""smart"". I have personally seen and held a Vienna Austria newspaper from 1967 (given to me by Mr. Fisher) where the Russians claimed to have ""invented the Space Pen"". If they were so keen on using pencils, why would they had made this claim.
As final proof, please go to http://www.thewritersedge.com/story.cfm and you'll see Russian astronauts using the Fisher AG7E Space Pen. I've had Russian Cosmonaut Anatoly Solovyev in my home after he flew this mission and he told me that the Russian space program has used the Fisher Space Pen for as long as he's been a Cosmonaut. In his words ""pencil lead breaks...and is not good in space capsule; very dangerous to have metal lead particles in zero gravity""
Jim Jobin, Owner.
*** Special thanks to Jeff Fink, formerly with General Electric's Special Materials Dept. Jeff provided some of the compositional background on graphite and it's physical attributes.