# Re: Mission of Gravity, China Lake style

Jeff Davis (jdavis@socketscience.com)
Sun, 12 Dec 1999 21:41:50 -0800

"Lucky, lucky, lucky, lucky,lucky,..."

```                             Sigorney Weaver as "Riply" in "Alien"

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Regarding centrifuging guppies and other critters IN A LIQUID MEDIUM to see how they tolerate g-loads

On Sat, 11 Dec 1999 07:19:04 -0800
"Michael M. Butler" <butler@comp-lib.org> writes:

<TEN MINUTES?!? Whoa, Nellie!!>

Which seems to suggest that ten minutes at 100 gees is some serious exposure. Perhaps. But let's have some context.

In spike's original experiment, he writes that he

>bought a dozen guppies, put em in a plastic thermos bottle,
>put the bottle in the centrifuge and spun em up to 100 g for 10
>minutes.

Now if the thermos bottle is upright at the bottom of the centrifuge, and if the liquid level is nine inches, then the hydrostatic pressure at the very bottom is (100 gees x .75 ft) the equivalent of a water depth of 75 ft. (If the two meter centrifuge had a two meter water column, the median gees for the column would be 50, and the pressure at the very bottom the equivalent of approx 350 ft of water.) Now guppies don't normally live at these depths, but all in all I would guess the stresses of such exposure--the hydrostatic stresses, that is-- to be utterly trivial. Whether for ten minutes or ten years. (After a while, they did stop swimming in spirals, didn't they, spike? )

A serious test would be to spin them up, and determine the locus of points--plotted as duration vs gee load (depth of the supporting liquid medium kept constant and at a minimum)--where they suffered some irreversible effect/injury . I wouldn't be surpised if it happened--for fish--around 5-10,000 gees.

Best, Jeff Davis

```	   "Everything's hard till you know how to do it."
Ray Charles
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