Feb. 24, 2000 NASA's "planet in a test tube" experiment has shown that microgravity -- the weightless environment inside an orbiting spacecraft -- helps scientists create more accurate models of planetary atmospheres and oceans. Scientists recently published results from this Space Shuttle experiment in a NASA technical document.
Because scientists can't yet travel to other planets, they build models like the "planet in a test tube" to simulate conditions on a planet. These sophisticated models help scientists study fluid movements in Earth's atmosphere and oceans and on other more distant worlds.
NASA's "planet in a test tube" -- the Geophysical Fluid Flow Cell -- was designed by Dr. John Hart, lead investigator for the experiment and a fluid physicist at the University of Colorado in Boulder. The experiment was flown on two Space Shuttle missions -- in 1985 and 1995. During the second mission, the experiment was operated in space by Dr. Fred Leslie, a co-investigator on the experiment and a fluid physicist at NASA's Marshall Space Flight Center in Huntsville, Ala.
"On the ground, it is impossible to create accurate models because Earth's gravity produces unrealistic fluid behavior on the spherical model," said Leslie. "In microgravity, you eliminate Earth's gravity, and can do experiments with artificial gravity to verify mathematical and computer models of fluid flows in planetary atmospheres."
Inside the Geophysical Fluid Flow Cell, scientists created models of Earth's climate and interior, the Sun's atmosphere and the atmospheres of other planets. Detailed results of the Geophysical Fluid Flow Cell experiments are published in NASA Technical Memorandum, NASA-TP-1999-209-576, which is available on the Marshall Technical Reports Web site at: http://mtrs.msfc.nasa.gov/mtrs/
How do you simulate something as big as a planet? The heart of the Geophysical Fluid Flow Cell is a nickel-coated, stainless steel ball about the size of a Christmas ornament. The ball is placed under a synthetic sapphire dome, and silicone oil placed between the two simulates the atmosphere of Jupiter, the Sun or Earth's molten mantle, depending on the experiment conditions selected by scientists. A temperature-controlled turntable spins the dome -- simulating planet rotation -- and an electric charge between the dome and the sphere serves as artificial gravity.
During the Geophysical Fluid Flow Cell's first flight, more than 100 experiments were conducted using the cell to simulate different conditions, and 50,000 images were recorded on 16-mm film.
"We were successful and made several observations of new convection patterns," said Hart. "Some of these are pertinent to our search for explanations of the key features, like zonal winds and jets, of Jupiter's atmospheric structure."
On the first flight, investigators didn't get to see what was happening inside their model until the Space Shuttle brought the film back to Earth. For the second flight, investigators added equipment so they could observe the model and change the parameters to create certain effects. Leslie was a payload specialist on the flight and operated the experiment in space.
"It was great to personally do the experiment," said Leslie. "The first flight was a little like running an experiment in the lab with the lights off. We had no indication how the fluid was responding to the inputs. During the second flight, both I and the scientists on the ground could see how the model changed as we changed parameters like rotation rate or temperature. Then, I could tweak the parameters to make the simulation more realistic."
During the second mission, 29 separate six-hour runs were completed with the Geophysical Fluid Flow Cell. "The influence of weightlessness on experiments was amazing to watch," said Leslie.
Dr. Tim Miller, another co-investigator on the experiment and an atmospheric scientist at NASA's Global Hydrology and Climate Center in Huntsville, developed and used computer models to predict the flows seen in the Geophysical Fluid Flow Cell experiments. He hopes that lessons learned in the study of the fluid flow cell dynamics can be applied toward a better understanding of such topics as the movement of Earth's continents and atmospheric dynamics on Earth and other planets.
His model successfully predicted that final flow patterns for some of the very slowly rotating cases could depend on how the experiment is started. This may be an important point in the discussion of the movement of continents in response to the steady pull of the viscous mantle beneath the continental plates. "There's a lot more science that can be obtained with the data and the models," Miller said.
The Geophysical Fluid Flow Cell experiment is managed by Marshall's Microgravity Research Program Office.
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