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Author Topic: elliptical orbits  (Read 12499 times)

space guy1

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elliptical orbits
« on: August 22, 2009, 08:32:53 AM »
is there a way to get a stable elliptical orbit?  whenever i make one it slowly becomes circular over about 10 orbits

witold

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Re: elliptical orbits
« Reply #1 on: August 22, 2009, 09:29:32 AM »
decrease mass of parent body

FGFG

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Re: elliptical orbits
« Reply #2 on: August 22, 2009, 09:44:38 AM »
is there a way to get a stable elliptical orbit?  whenever i make one it slowly becomes circular over about 10 orbits

It is strange. Theoretically the orbit (without any layer) should always remain stable because there is no friction (kinetic-potential energy remains constant).

space guy1

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Re: elliptical orbits
« Reply #3 on: August 22, 2009, 09:46:38 AM »
decrease mass of parent body
i tried that and it doesn't work the same thing happens

atomic7732

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Re: elliptical orbits
« Reply #4 on: August 22, 2009, 11:44:24 AM »
Maybe the timestep is to high?  ???

space guy1

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Re: elliptical orbits
« Reply #5 on: August 22, 2009, 12:43:51 PM »
possible but i don't think so.  i usually have the time step on auto.

witold

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Re: elliptical orbits
« Reply #6 on: August 22, 2009, 01:40:56 PM »
decrease mass of parent body
i tried that and it doesn't work the same thing happens

Decrease the mass of parent body about 30%-50% turn timestep faster(as you like) and don,t press "orbit parent" or "orbit all"

space guy1

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Re: elliptical orbits
« Reply #7 on: August 22, 2009, 02:06:19 PM »
same thing happens.  i never press orbit buttons when i try to get an elliptical orbit.  what happens if it matters is the orbiter will orbit smoothly but on every orbit the eccentricity drops to like 9/10 of what it was.

witold

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Re: elliptical orbits
« Reply #8 on: August 22, 2009, 02:38:44 PM »
same thing happens.  i never press orbit buttons when i try to get an elliptical orbit.  what happens if it matters is the orbiter will orbit smoothly but on every orbit the eccentricity drops to like 9/10 of what it was.

Strange. But i know is this possible i show you

1. Launch "Universe Sandbox"
2.Open "Our Solar System"
3.Change Mass of Sun from 1.00 suns to 0.70
4.The orbits of plants should more eliptical

monmarfori

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Re: elliptical orbits
« Reply #9 on: August 22, 2009, 03:11:19 PM »
Nereid have the elliptical orbit.

space guy1

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Re: elliptical orbits
« Reply #10 on: August 22, 2009, 03:28:46 PM »
same thing happens.  i never press orbit buttons when i try to get an elliptical orbit.  what happens if it matters is the orbiter will orbit smoothly but on every orbit the eccentricity drops to like 9/10 of what it was.

Strange. But i know is this possible i show you

1. Launch "Universe Sandbox"
2.Open "Our Solar System"
3.Change Mass of Sun from 1.00 suns to 0.70
4.The orbits of plants should more eliptical
yeah they start out elliptical but as the planets orbit more the orbits get more circular.

Dan Dixon

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Re: elliptical orbits
« Reply #11 on: August 22, 2009, 08:33:41 PM »
is there a way to get a stable elliptical orbit?  whenever i make one it slowly becomes circular over about 10 orbits

This is a bug that will be fixed in version 2. It's the result of the simplistic integration method currently used by Universe Sandbox. Version 2 will default to the Runge-Kutta 4 method which doesn't suffer from such noticible integration errors.

Are you turning on auto time step? This seems to cause use elliptical orbits to become circular.

space guy1

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Re: elliptical orbits
« Reply #12 on: August 23, 2009, 06:55:35 AM »
is there a way to get a stable elliptical orbit?  whenever i make one it slowly becomes circular over about 10 orbits

This is a bug that will be fixed in version 2. It's the result of the simplistic integration method currently used by Universe Sandbox. Version 2 will default to the Runge-Kutta 4 method which doesn't suffer from such noticible integration errors.

Are you turning on auto time step? This seems to cause use elliptical orbits to become circular.
so to fix this problem dont turn on auto time step?

Dan Dixon

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Re: elliptical orbits
« Reply #13 on: August 23, 2009, 01:22:59 PM »
so to fix this problem dont turn on auto time step?

Yes. I think this will help reduce the problem.