Honey I Shrunk the Cups!

On November 6th we  opened the JR moon pool to deployed the Vibration Isolated Television (VIT) sub-seafloor camera down to 484 meters below sea level. While testing the VIT and it’s new fiber optic cables our Styrofoam cups were allowed to hitch a ride. The JR aims to be 100% green and does not use Styrofoam cups. These cups were brought on board specially for experimenting with sea level pressure. Let the experiments begin!

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                                                                                          Protecting cups with bubble wrap and guarding them with my life!

Phase I: How did we get 12 cups from the USA, to Darwin Australia and then finally on board the JR?

We had large cups decorated by student in Pittsburgh and then dropped off in Washington DC where I prepared the for travel to Australia. I carried the cups during my 26 hour travel from Washington D.C. to Sydney Australia, then on to Darwin. Keeping my eyes on these precious cups at all times, and remembering to take them on and off 3 different flights! To get the scientists involved in this experiment I purchased additional cups in Darwin. Now we just had to wait until the moon pool was opened for testing. 

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8oz and 16 oz cup decorated and ready for submersion

Phase II: What do the cups look life before they head to the seafloor?

First I invited scientists and technical staff to decorate their cups using permanent markers. Some scientists got very creative and each cup was personalized. 15 additional cups were added and we now had a total of 30 cups to use for our pressure experiment.

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Lisa C. getting the cups positioned just right in the laundry bags.

Phase II: Why send cups down to the seafloor?

We wanted to know what would happen to the cups as they travel to the seafloor. I filled two laundry bags with cups. Then Lisa C.  aligned the cups just right in the bags. All cup opening were facing up, separated, and unstacked. Next we had to secure the cups to the VIT for travel.

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Assisting Lisa C. as she ties the bags of cups to the VIT

Phase III: How to we get the cups safely to the ocean floor and back?

We put all the cups laundry bags specially designed by Lisa C who strung the bags to give each cup a compartment to hang in. Once all the cups were in the laundry bags we headed to the moon pool area where we strapped the bags to the VIT equipment.

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JR moon pool open and VIT camera being lowered with bags of cups attached.

Research equipment must be designed to deal with enormous pressures encountered in the depth. Instruments that work well at the surface may collapse or break when subjected to increasing pressure. (NOAA)

Phase IV: What happens to Styrofoam cups under increasing pressure?

When the cups resurfaced 2 hour later they had shrunk. What caused the cups to shrink? At sea level the pressure is 1 atmosphere and is equal to the earth’s atmosphere. The pressure increases  1 atmosphere every 10 meters of water depth. At a dept of 500 meters the pressure will increase by approximately 50 atmospheres or 50 time greater than the pressure at sea level. (NOAA)

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8 oz cup before and shrunken cup after travel to the seafloor under a total of 50 atmospheres!

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Phase V: How much less volume can cups hold (% capacity) after shrinking?

Pressure is applied to the cup on all sides and this changes not only it’s size but the volume it can hold. A easy way to measure decrease in capacity is to fill the cups. An 8 oz cup holds 240ml of water and the shrunken cup holds 40ml of water. Using simple math you can compare, the 8oz cup now hold 1.3oz and capacity has decreased by approximately 83%! You can do this experiment with all the shrunken cups to get average % capacity decrease.

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How much water does the cup displace?

Phase VI: What % did the cups shrink?

To calculate the cup’s physical change i.e. Styrofoam volume, you can measure how much water a 8 oz displaces verses the shrunken cup. You will need something to weigh the cups down. The 8oz cup displaces ~45ml of water and the shrunk cup displaces ~8ml. The shrunk cup only displaces 11% , which means that the Styrofoam volume decreased by approximately 82%!