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Re: AO40: status

On Sat, 6 Jan 2001, Phil Karn wrote:

> Nope again. As the propellant drains outward, it gets accelerated by
> the spacecraft body. This slows down the spin rate. As it dribbles off
> the end, it continues in a straight line tangential to the point of
> departure.

Hummh...  You are thinking in terms of a liquid I think.  I am thinking in
terms of a gas (I assume that all of the liquids instantly vaporize to a
gas in the vacuum at the point of the leak (near the center of the
spacecraft).  At that point, the gas is not in contact with the spacecraft
and so it does not take away any angular momentum as it finds its way out
of the bird through whatever holes it finds.

Kind of like the fly flying around the cockpit of Lindberg's plane.  Does
it add to the weight of his plane or not?

But I guess it does take a finite period of time for any molecule of gas
to get through the compartments and out, and by that time it has picked up
the angular momentum of that compartment (no matter how small)...

So then it must have all escaped near the center..

> So if AO-40's spinup was caused by the simple movement of propellant
> mass, it must have moved from the fuel tanks closer to the Z axis.

Yep, we certainly agree on that point.

de WB4APR@amsat.org, Bob

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