Saturday, August 23, 2008

Practice makes Perfect

The rollercoaster ride that is the runup to the rollercoaster ride we want to take threw us for another loop when, the night before we planned to drive from Las Vegas to Los Angeles, we got a call that "G-Force One" (shouldn't it be G-Force Zero?) had a mechanical issue that needed repairing, and the Saturday flight was cancelled. There was, however, a chance that it could be rescheduled for Sunday.

After 24 hours of angst, we got the word that all was well and we could indeed fly on Sunday. So we are now skulking in a secret lair in Gendale CA (we were promised a stimulating hive of scum and villiany; so far, not so much), counting down the hours, and half-expecting that a massive earthquake will devastate Burbank Airport overnight.

In the meantime, we did several practice runs of the several experiments we are going to attempt. Here you can see James and I running through our core experiment, "Menticulation of Aspartame-sweetened Cola-flavored Carbonated Beverages in a Microgravity Environment".

After much thought, we have decided not to repeat the prior experiments that have been done in 1G, but instead do something that can only be done in ZeroG.

Prior research by Hyneman, Savage, et al. and others has demonstrated conclusively that menticulation is largely a physical reaction. The mentos, when introduced to the cola, provide a large number of nucleation sites because they are quite rough on the microscopic level, and thus permit the rapid growth of bubbles of carbon dioxide, which is in solution in the soda. In addition, the aspartame sweetener used in diet soda, as well as some other ingredients, reduce the surface tension of the liquid, making it easier for the bubbles to form.  The result is the pressurized shower of slightly minty soda that we all know and love.

However, there may be another important process that takes place during menticulation that has not been addressed by prior research -- convection. Consider than when the bubbles are formed, they will naturally rise to the top of the bottle (since they are less dense than the soda), and more importantly, this will draw more cola into contact with the mentos. But in ZeroG, there is no up and down, and so the bubbles have no inherent tendency to rise. So what will happen? Will the process continue, but at a slower rate? Or will the initial bubble formation effectively cut off the reaction entirely by isolating the mentos from the cola? Might we even end up with a thick skin of cola surrounding a bubble of CO2?

So it seems that the cola and mentos idea has gone from just being a cute stunt to being real science. If we get an interesting effect, we will be discovering something that nobody knew before, and adding, in a small way, to the sum of human knowledge.

In the above photo, you can see our experimental apparatus. We are using a plastic glove-bag to contain any spills, and have added an 8x10 acrylic window to it with heavy duct-tape. Taped to the window is a wide-angle rubber camera sunshade that we can screw the camera into.  Inside the bag are several ziplock sub-bags that will contain our materials. The cola is contained in a small plastic bottle with a nipple attachment that will allow me to dispense small amounts of soda in front of the camera port, at which point I will insert a mento into the cola using a ziptie with a small blob of artist's clay on the end.

Depending on how the first trial works, we'll try it again using a bigger blob of cola, and think of something on the spot to do.

On a side note, recent pictures I have seen of G-Force One indicate that the main cabin does have some windows.  If so, we should be able to get enough natural light to film at 300 frames per second!

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