Re: gas giants

> Let me put it another way (than my prior
> Jupiter-esque question):
>
> 1) What is a reasonable guess of core radius
> and edge of atmosphere radius (if we assume
> 140K km for Jupiter, 7" to edge of
> atmosphere.... but how much is core?).

http://quest.arc.nasa.gov/galileo/Galileo-QA/new/Jupiter_s_surface.txt
"We are not even sure if Jupiter has a _solid_ core or
not.  If it does, its radius is estimated to be only about 7000 km
while
the equatorial radius of the planet's entire envelope of atmospheric
gas
is about 71,400 km (compared to 6,000 km for the Earth).  This is the
radius out to the top of the atmosphere to the one-bar atmospheric
pressure level, i.e, the "altitude" above the center of Jupiter where
the
pressure is the same as that usually encountered at the Earth's
surface.
So you would have to dive down about 60,000 km into the planet before
getting to a solid surface"

> 2) What is the surface gravity of Jupiter guessed
> to be?

If we take earth's mass and radius as 1 unit then we can plug 318
units for Jupiter's mass and 11.3 units for its radius into the
gravity proportion. Squaring the radius and dividing into the mass we
find how much stronger Jupiter's surface gravity is than earth's--ie
about 2.5 Earth at the cloud tops.
When you're on Earth's surface, almost all the mass is under you--the
atmosophere doesn't count for very much--so you can treat the gravity
as coming from the center of mass.  However, with Jupiter, when you
get to the hypothetical solid surface, as lot of the mass will be
above you.  The gravity might not be as much as you'd expect.  Of
course, the air pressure will crush you flat...From the same site
cited above: "The Galileo probe that landed in Jupiter's atmosphere
last December [96] made measurements only within the upper 150 km or
so of the atmosphere before it melted in the extreme heat and
pressure"

> 3) Would there be any combat possible in the
> atmosphere or would sensors and such
> effectively be blind?

The difference in environments might be analogous to the difference
between aerial and submarine.  My future history of Alarish includes a
battle in which AE ships hid in the outer atmosphere of a jovian, then
ambushed the invading PAU, but I don't think there's be any combat
there.	And you'd want a streamlined ship.