Tag Archives: pencil

russian space writer

Myth busted: Americans spent millions to make a pen that would flow in space — the Russians used a pencil

Legend has it that NASA spent millions to develop a ballpoint pen whose ink could flow in zero gravity. The more pragmatic Soviets used a pencil. It’s a great story that reminds us that a complicated problem doesn’t necessarily entail a complex solution. Alas, this allegory is in fact a myth and a terrestrial graphite pencil is actually a bad idea.

russian space writer

Like Soviet cosmonauts, the NASA astronauts originally used pencils too. In 1965, for instance, NASA used mechanical pencils for the Project Gemini mission. For that particular order, the American space agency paid $128.89 per unit, which sparked a controversy at the time since the public saw it as a frivolous expense. Pressed, NASA used less costly items.

These were still the early days of human space exploration, but engineers already knew that normal pencils could be dangerous. Graphite, the stuff pencil lead is made of, is highly flammable and micro-sized graphite shavings can easily float about a spacecraft, infiltrate sensitive instruments and jeopardize a mission.

Maybe inspired by the news reports that ridiculed NASA’s expensive pencils, inventor Paul C. Fisher and founder of the Fisher Pen Co. designed a ballpoint pen that could work in space. Helped by a pressurized ink cartridge, the AG7 Fisher Pen could be used to write in a weightless environment, underwater, in other liquids and at temperatures ranging from -50 F to +400 F.

Initially, Fisher and colleagues found the pressurized cartridge was great at pushing the ink out of the pen. But the ink also leaked uncontrollably.  Fisher found a workaround by changing the ink. He used a thixotropic ink — a gel at rest that turns into a liquid under pressure, like toothpaste. This thicker ink didn’t leak anymore and passed NASA’s rigorous tests. Interestingly, this solution came to Fisher in an esoteric-like dream in 1965.

“About two nights [before] I had an interesting dream. My father had died about two years before, and in that dream, he came to me and said Paul, if you add a minute amount of rosin to the ink, that will stop the oozing. I told the chemist about that, and the chemist laughed! He said that won’t work. He tried every type and quantity of rosin. Three months later he came back to me and he said I was right! He said he was trying to find a way to make rosin work, but then he realized that I meant resin! He used two percent resin, and it worked fine….I called NASA and told them we could do it, and we developed the most valuable patent in all of the pen industry,” Fisher said in an interview. 

The project reportedly cost $1 million to research, but all on Fisher’s dime. NASA did not contribute money, nor did it ever expressly asked Fisher to make the pen. Nevertheless, they made good use of it.

In 1967 NASA managers agreed to equip the Apollo astronauts with these pens. About 400 units were ordered at a price of $2.39 per pen, with a 40% bulk discount. The Soviet Union also purchased 100 of the Fisher pens, and 1,000 ink cartridges, in February 1969, for use on its Soyuz space flights. That doesn’t add up to a profit, but Fisher more than made up for it indirectly from all the publicity. Everyone wanted to write with the same pen used by astronauts.

For decades, both Americans and Soviets continued to use the Fisher space pen. Later, Fisher developed a new space pen, the CH4, that was used during NASA’s space shuttle missions and on the Russian space station, Mir. You can buy your own for 44 bucks from the Fisher store.

 

eraser gif

How does an eraser work?

What happens when you write?

Although we call the black stuff in pencils “lead,” it’s not the real metal known as lead. It’s actually a mineral called “graphite,” which is made up of carbon. When you write with a pencil, graphite particles from the pencil rub off and stick to the fibers of the paper you’re writing on.

What do erasers do?

When you rub an eraser across a pencil mark, the abrasives in the eraser gently scratch the surface fibers of the paper to loosen the graphite particles. The softeners in the eraser help to prevent the paper from tearing. The sticky rubber in the eraser grabs and holds on to the graphite particles.

The physics

Erasers work because of friction.

As the abrasives in your eraser are rubbed against paper, friction produces heat, which helps the rubber become sticky enough to hold onto the graphite particles. As the rubber grabs the graphite particles, small pieces of combined rubber and graphite get left behind. That’s the “stuff” you brush off of your paper when you’re finished erasing.

[Source]

 

Could you balance a pencil on a one-atom thick tip?

It’s Saturday, so time for some fun physics. This non-trivial question is often asked in international physics contests and requires a bit of out of the box thinking. Let’s imagine a   perfectly symmetrical pencil in terms of density, whose tip – just one atom thick of graphite – lies on a perfectly smooth surface. We want it to be perfectly still and perfectly upright to balance on the surface. The real world isn’t perfect of course, but these sort of assumptions are important to make the problem tractable since we can describe the system’s behavior through equations that can predict what happens next, like will the pencil balance or not? Well, first of all the pencil balancing act fails almost immediately depending on far you want to go with “perfect” model assumptions. One single photon hitting the pencil is enough to unbalance the graphite rod. Then there are tidal forces exerted by the moon and the sun. Then of course, given Earth’s gravity, only one atom thick tip can’t sustain the weight of a pencil and would break. For graphite, the thinnest tip you could use to withstand the weight of a pencil is 0.01 millimeters, which is amazingly sharp by not nearly atomic.

Even if we cool to absolute zero, vacuum and put the pencil in a pitch black room, in the end, it would all boil down to quantum mechanics toppling our pencil. A clever Physics Stackexchange user called Floris sums it up for us:

Momentum and position form a conjugate pair. ΔxΔp.

Angular momentum and angular position form one too. ΔLΔΘ

This doesn’t guarantee that angular momentum and angular position will be non-zero. It is an uncertainty – The actual values can be anything, including 0.

But it does prevent you from arranging them both so the pencil stays upright. Furthermore, if you ask what the probability of finding both values very close to 0, you find that it is very small. In the limit, infinitely improbable.

If it turns out that L=Θ=, and you plug in reasonable values for the mass and length of the pencil, you will find it falls over in a few seconds.

Another very in-depth explanation of the one-atom-thick pencil problem can be found at The Virtuosi.