glyphstrip FAQ button
Halo.bungie.org
glyphstrip
Frequently Asked Forum Questions
 Search the HBO News Archives

Any All Exact 
Search the Halo Updates DBs

Halo Halo2 
Search Older Posts on This Forum:
Posts on Current Forum | Archived Posts


Re: Chaotic Motion?
Posted By: Toby Haynes <thaynes@ca.ibm.com>Date: 10/22/99 9:21 a.m.

In Response To: Chaotic Motion? (Loren Petrich)

> Halo's orbit around Jonesworld is either not chaotic or chaotic
> within a limited range (its position in orbit may be chaotic
> over large timescales, but this will have little effect on its
> average orbit distance) but the same cannot be said of its
> rotation.

Purely from a 'build-yourself-a-world' perspective, I would assert that Halo's orbit would have been designed to be stable - you don't commit the sort of resources needed to build something like an orbital only to see it float off into space or crash into the local star.

> It will have rotation around both its axis of symmetry and two
> axes perpendicular to it; the latter kind of rotation is most
> familiar as precession. Axial rotation will be constant, aside
> from tidal drag and collisions with other objects, but
> precession can be variable.

Add nutation as well - the oscillation in the axis of rotation. The Earth does this, on some timescale (40,000 years? - I forget)

> If Halo's angular velocity of rotation is significantly greater
> than its orbit angular velocity, then its precession is likely
> to be much like the Earth's -- its axis makes a wobbly circle.
> However, if its rotation velocity is less, then its precession
> will be chaotic tumbling with a chaos timescale comparable to
> Halo's orbit period. Also, the locally-felt gravity
> (Jonesworld's tides) would vary in strength and direction, and
> be greater than Halo's rotational centrifugal force.

Well - given the size of the ring and a desired gravity at the surface, you can easily calculate the rotational velocity and put upper and lower bounds on it (assume 0.2G to 2G as a reasonable range for a human-class colony). You could then go on and calculate the height of the retaining walls at the edges of the Orbital which keeps the atmosphere in - unless there is a 'roof' on the Orbital, which is an unlikely idea. You may choose to disregard the mass of the retaining walls in the calculations of tidal forces exerted by other planets by assuming that the mass of the walls is negligable next to the actual landmass.

> Thus, for Halo's contents to be retained or at least not
> upended, Halo must spin faster than it orbits.

I disagree, or at least I think this statement is ambiguous - to retain the atmosphere, all you need is a critical rotation speed for the Orbital assuming that the attractives forces acting on the Orbital due to the star and other local planets are less than 0.01G' where G' is the surface gravity on the Orbital. The rotation speed is then a function of the temperature of the atmosphere, the height of the retaining walls, the maximum allowed atmospheric leakage into space and the desired surface gravity bounds.

> Maybe I should create some interactive Halo simulator and code
> it as a Java applet.

You'll end up with lots of variables :-)

Be careful with floating point roundoff and errors - it's very easy to end up with errors building up to significant degrees very quickly unless your differential equation solver is either very accurate, or has errors which average to zero over time. As a good setup test of your D.E. solver, pump the Solar system into it and make sure it doesn't fall apart too quickly. I've seen nightmare scenarios of solar system stability collapse turn out to be a 10e-9 floating point error per calculation :-)

Have fun!

Toby

Message Index



Replies:

Chaotic Motion?Loren Petrich 10/21/99 2:31 a.m.
     Re: Chaotic Motion?Butcher 10/21/99 4:25 p.m.
           Re: Chaotic Motion?Loren Petrich 10/21/99 6:09 p.m.
                 Halo's MotionNathan 10/22/99 9:26 a.m.
                       Re: Halo's MotionLoren Petrich 10/22/99 4:51 p.m.
                 Re: Chaotic Motion?Butcher 10/22/99 5:51 p.m.
     Re: Chaotic Motion?Dispatcher 10/21/99 8:30 p.m.
           Re: Chaotic Motion?Loren Petrich 10/22/99 12:08 a.m.
                 Re: Chaotic Motion?Daft Shadow =PN= 10/22/99 12:43 a.m.
                       Halo Precession SimulatorLoren Petrich 10/22/99 2:01 a.m.
     Re: Chaotic Motion?Toby Haynes 10/22/99 9:21 a.m.
           Re: Chaotic Motion?Loren Petrich 10/22/99 4:09 p.m.



contact us

The HBO Forum Archive is maintained with WebBBS 4.33.