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Physics students fly on NASA's DC-9 "Weightless Wonder"
The flights were a tremendous success! Click here for images from Flight Day One.
"Splashless in Space: The Impact Behavior of Large Droplets on a Rigid Surface in Low- Atmosphere, Low-Gravity Environments." There are two very good reasons why this experiment has a title that takes ten minutes to say: 1) When the results are published in all the most prestigious Scientific Journals it will be important that other scientists are able to tell at a glance exactly what the experiment studied. 2) It sound REALLY COOL!
The Microgravity Team From left to right: John Stupak, Mike Zaffetti, Brendan Hermalyn, Jessica Kurose
What the experiment is all about
In the words of the students who developed the experiment: "We intend to investigate the physics of large scale liquid drop impact upon a smooth dry surface. As a drop of liquid impacts a smooth dry surface, a crown shaped splash emerges as the drop collapses. A rather surprising phenomenon, however, was discovered in 2005 (by Xu, Zhang and Nagel, University of Chicago); when the atmospheric pressure around the impact is decreased, the splash ceases to occur."
The image to the right was taken by Harold E. Edgerton using strobe lights and very high speed cameras to "freeze" the action. Edgerton invented a method of capturing images of things that happened too fast for the human eye to see. This image of a drop of milk striking a surface displays the now famous "crown splash". Most scientists who studied droplet behavior believed that the size and shape of the splash was chiefly effected by the material making up the droplet (in this case milk) and the texture of the surface it was landing on (in this case a smooth table top), there was little attention being paid to the gas (usually air) that filled the space in which the splash was forming.
In 2005 scientists at Chicago University made a surprising discovery involving the importance of air pressure in the formation of the corona splash. Look carefully at the photo to the right, the red arrows are pointing to a tell tale gap between the surface and the splash. That gap is believed to be caused by air trapped between the droplet and the surface.	.
The series of photos below illustrates what the team at Chicago University discovered. The top row of images show a droplet of ethanol hitting a dry surface with the air pressure inside the chamber equal to the pressure of the air you are breathing right now. In the bottom row of images the air pressure in the test chamber is about 1/6 the pressure at sea level, at this pressure the droplet no longer splashes it simply spreads out across the surface is a very uniform way.

100 kPa or 100 kilo pascal is roughly equal to one atmosphere, or the air pressure at sea level. As altitude increases air pressure drops so that at the top of Mt. Everest the air pressure is about 30 kPa or about 1/3 the air pressure at sea level. The pressure inside the chamber when the droplet of ethanol no longer splashes (bottom row of photos) is almost half the air pressure at the top of Mt. Everest or about 1/6 the pressure of the air you are breathing right now!
What are the Fairfield University students doing on board the "Weightless Wonder"?
On earth a droplet formed on the end of a needle has a limited size, once it reaches a certain size (depending on the needle diameter and surface tension of the liquid) gravity pulls it free of the injector and it falls to the impact surface. Because of this the Chicago team was limited to drops no larger than 3.4 mm in diameter (about 1/8 of an inch). Based on the data they were able to collect they developed a mathematical model that describes how the splashing is related to air pressure. The Fairfield University Microgravity Team will be testing this model against larger drop sizes. In the micro gravity environment on board NASA's DC-9 they will be able to form drops up to five times larger than can be formed in an earthbound lab.

To visit NASA's Microgravity University web page click here	To visit the Microgravity Team's web page click here

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