Re: [GZG] Space Terrain

On Friday 08 May 2009 20:51:42 Tom B wrote:
> Tomb --> I was meaning your typical collapsed star black hole, rather
than
> imploded planets or the like.

Problem is, a collapsed star wouldn't be playable anywhere close
to it, hence my concentration on 'small' black holes. Neutron
Stars and White Dwarfs would have similar problems.

> If the Earth was squashed into a black hole, the gravity effects
> would be the same as on my chart, as long as you stayed outside
> the original diameter of the planet. Since black holing the Earth
> shrinks it down to only a few kilometres, you can get a lot closer
> than this, so the gravity effects go up dramatically.
>
> Tomb --> To? Example? Let's say I squish an Earth sized and massed
Class M
> planet (they're everywhere, after all). What kind of effects would I
get
> inside the 13" spherical region that was my former planet?

Gravity increases/decreases according to the square of the distance.
Halve the distance, quadruple the force of gravity. Reduce the
distance by a thousand, increase gravity by a million. So, according
to my chart on: http://www.glendale.org.uk/ft/planets.html

The 4" band for Earth is measured from the surface of the Earth.
That's about ~8" from the centre, and gives a gravitational pull of 6".
Halve the distance down to 4", and that quadruples to 24" pull. Down
to 2" and you're at 96".

Similar for the sun, if the Sun is squashed down you work out where
the new surface is and multiply things up. The figures I've given
have been averaged, rounded and possibly fudged slightly for
playability, so probably aren't good starting points for doing this.

> Pulsar's often rotate with periods measured in seconds (or less), so
> any arc they sweep out will cover the entire table many times each
> turn.
>
> Tomb --> Sure, but is it really a damaging radiation? Out how far? How
> damaging? In SFB, I seem to recall fighting near one was a real ship
> grinder.

Radiation and such isn't my strong point. Probably the crew would die
long before the ship was harmed. Then again, maybe energy shields
protect them.

> If you look at my chart, at the surface of Jupiter, you're being
> pulled 20" into the planet every turn. Saturn is a more sedate
9"/turn.
> Either way, if you're hitting the atmosphere at orbital velocities
> it's probably going to hurt.
>
> Tomb --> But is that relevant directly? The atmosphere of a gas giant
> extends quite far doesn't it?

The 'surface' of gas giants is actually the top of the atmosphere.
In the real world, atmospheres don't end neatly of course, so there
will be plenty of hydrogen above this point, just below the density
that astronomers consider an 'atmosphere'.

> If so, doesn't that mean that a ship could 
> skim the atmosphere for fuel without exposing itself to the massive
> gravitation? (Of good old MT established you needed thrust 4 or
something
> to land on a standard gravity world, so heavy gravity would be B-A-D
news.)

My figures assume 8 thrust = 1g. This is low compared to MT, but
gives bigger (more interesting) gravitational effects. With a
Traveller-like background, you might have 1 thrust = 1g, which
makes it much easier to keep away from planets.

There's all sorts of definitions of 'land' to play with. The Apollo
re-entry modules had about zero thrust, but were more than capable
of landing safely on Earth. Taking off again tends to be the tricky
bit, and requires thrust.

You don't need thrust however to not crash into the planet, just
orbital velocity. Which, for Jupiter, means you need to hit the top
of the atmosphere fast to skim up fuel.

> And would 'hitting the atmosphere' to skim for gas (almost like
entering an
> orbit) be really any worse than re-entry? The space shuttle survives
that
> and I assume any GZG ship that can land would need to be able to. If
you
> hit the atmosphere at other speeds, notably off from the orbital
speed, I
> can see bad things happening more easily.

If you could stay in the upper atmosphere where it's thin, then
it should be gentler then full re-entry.

-- 
Be seeing you,			       http://www.glendale.org.uk
Sam.			    Mail/IM (Jabber): sam@glendale.org.uk 
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