Gravity Simulator http://www.orbitsimulator.com/cgi-bin/yabb/YaBB.pl General >> Discussion >> rotational axis precession? http://www.orbitsimulator.com/cgi-bin/yabb/YaBB.pl?num=1503857389 Message started by selden on 08/27/17 at 11:09:49

 Title: rotational axis precession? Post by selden on 08/27/17 at 11:09:49 Would it be possible to enhance GravitySimulator to show the precession of a body's rotational axis? Or to show how an oblate primary might affect the orbits of its moons?This would require some way to describe an object's shape and mass distribution. A typical set of options might make it possible to configure an oblate spheroid similar to the Earth (to simulate the precession of its axis) or Saturn (to simulate the effects of its shape on its rings), for example.At the moment, I'm particularly interested in simulating how a multi-star system might affect the precession of a torus. Presumably approximating the shape of a torus by a highly oblate sphere might be reasonable.Alternatively, can you recommend any software which might be available to do this?Thanks for whatever help can be provided.

Title: Re: rotational axis precession?
Post by Tony on 08/27/17 at 15:29:42

"Off the shelf", Gravity Simulator can not do this. But you may be able to do this in the new broswer version, as the Autopilot lets you write scripts for the program.

For example, add the following code to Auto Pilot > Per Iteration:

Code:
 objMass[1] = 332946.050894784 - 1.05507125608548E-06 * elapsedTime;

This causes the Sun to gradually lose 10% of its mass over a period of 1000 years, making the planets slowly spiral out.

Use this program as your starting point: http://orbitsimulator.com/gsim.html
When you save your simulations,it saves them on my server and provides you with a link.

Properties of objects available to you in the Autopilot are:
objx[] // object's x-position in meters.
objy[] // object's x-position.
objz[] // object's x-position.

objvx[] // object's x-velocity in m/s.
objvy[] // object's x-velocity.
objvz[] // object's x-velocity.

objMass[] // object's mass in Earth masses.
objDiameter[] // object's size in meters.
objName[] // the object's name.
objColorRed[]; objColorGreen[]; objColorBlue[]; // the object's RGB colors.
objShadowRed[]; objShadowGreen[] ; objShadowBlue[] ; // the color of the dark side of the object when "Phases" is selected
objLabelRed[] ; objLabelGreen[]; objLabelBlue[]; // the color of the object's label
objTrailRed[]; objTrailGreen[]; objTrailBlue[]; // the color of the object's trail
objSubZRed[]; objSubZGreen[]; objSubZBlue[]; // the color of the object's trail when it is below the ecliptic plane

elapsedTime // time since the beginning of the simulation in seconds
many others too. Virtually any variable in the program is available for you to read or modify. So if you try this, and you need help, let me know.

Axis is not a defined property, so you're going to have to get creative. Perhaps create an object out of multiple objects, and compute your own forces and torques.

 Title: Re: rotational axis precession? Post by selden on 08/28/17 at 02:49:11 Thanks for the suggestion!