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Unstable orbits... Why use a halo orbit?
Posted By: Noctavis =PN= <noctavis@paxnimbus.com>	Date: 12/21/99 6:31 p.m.
In Response To: Re: Placing a satellite in the center of the Halo (Butcher) > Perhaps you miss my point... yes, there is an axis where there > is zero net gravity from the Halo. However it is dynamically > unstable; any small deviation from the axis will cause an > increasing acceleration further out, until the object smashes > into the surface of the Halo. > This will be exacerbated by local density variations on the Halo > (e.g. between mountains and seas). Yes, it's unstable... such an object would not be able to stay there until the stars go dark, unless it had some sort of stabalizing system. It's still an excellent solution... and it would require less work to maintain than other positions very close to the Halo. > Couple of problems with this. The Halo isn't actually sitting > centered on the Lagrangian point. It is orbiting this > theoretical point at an unknown distance, in a slow orbit known > as a 'halo orbit'. > Perhaps more importantly, any forces that are present due to > Threshold and Seropia will be applied equally to the Halo and > the satellite. So it makes no sense to talk about the position > of the satellite with respect to Threshold and Seropia (which > determine the location of the Lagrangian points) determining the > stability of the satellite with respect to the Halo. Aha... you've got me there. (Puts a chalk mark under Butcher's name) I remember Nathan/I4's post about that, but I hadn't thought about it at the time of the previous post. ;-p I'm also wondering about the Halo orbit. For one thing, IS it more stable than plopping something in the middle of a Lagrange point? The Lagrange point we're talking about for the game Halo is L1 - one of the more unstable such points.... L4 or L5 would be a much better (more stable) choice for placing an object unless you have a special purpose for keeping something BETWEEN two objects. Quoting from one of the sites that describe a Halo orbit: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We ordinarily think of orbits as circular paths (actually, elliptical paths) an object follows round and round a much more massive object--such as a space ship or the Moon orbiting around the Earth, or the Earth orbiting around the Sun. But any point of gravitational stability can have objects in orbit around it. For example, there is a point in space between the Earth and the Moon where the gravitational attractions of these two bodies are in balance against one another. This is called a Lagrangian point, and it is possible for an object to be in stable orbit around this point. Such an orbit is called a halo orbit--there is nothing in the middle of it but empty space. The plane of the halo orbit is perpendicular to the axis between the centers of the Earth and the Moon. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Note that it says "stable orbit." More stable than being in the center of L1? Anyone? And just to make sure we're one the same sheet of muzak, are we talking about the central lumen of the Halo being in orbit around the Lagrange point, and not actually being AROUND the lagrange point? No - I'm not being difficult or stupid here... One would consider the location of the Ringworld in the Niven novels to be an orbit, correct? Is it possible to place a solid band of matter along the path of an orbit? Yes... but it -would- have some instability. > The only exceptions to this are tidal forces, which are small in > magnitude and would probably only be noticeable if the satellite > - Halo forces were zero. Tidal forces are interesting to think about. I'd like to know just how massive Threshold is, and what the rest of the Soellar system looks like. We recently obtained some beautiful shots of volcanic activity on Io... which is constantly in a state of upheaval as a result of tidal forces in a near-Jovian orbit. Another question to pose to our amateur orbital mechanics: Does being in a Lagrange or Halo orbit significantly reduce tidal forces? I tend to think not. We're talking about stable areas in space where certain forces between two or more bodies are nearly in balance, but there are still variations from one point to another within this region of space.... The forces may not be evenly distributed when you're talking about an object that is larger than a certain size. -Noctavis

Message Index

Human Space Capability	Napalm Loon	12/17/99 7:33 a.m.
...But where would they orbit?	septimus	12/17/99 11:39 a.m.
Re: ...But where would they orbit?	Grey	12/17/99 12:40 p.m.
I'm dissapointed in you guys...	Maxaminus	12/17/99 2:05 p.m.
Two possible definitions.	Dispatcher	12/17/99 9:33 p.m.
Re: I'm dissapointed in you guys...	SiliconDream =PN=	12/17/99 9:43 p.m.
Re: ...But where would they orbit?	Jägermeister	12/17/99 1:22 p.m.
Re: Internal orbits	Mark Levin	12/17/99 2:15 p.m.
Re: Internal orbits	Mage	12/17/99 2:32 p.m.
Re: Internal orbits	Mark Levin	12/17/99 2:38 p.m.
Re: Internal orbits	Mage	12/17/99 4:13 p.m.
Re: Internal orbits	Maxaminus	12/17/99 4:45 p.m.
Re: Internal orbits	Mage	12/17/99 11:06 p.m.
Re: Internal orbits	Mark Levin	12/18/99 12:42 a.m.
Re: Internal orbits	Mage	12/18/99 11:31 a.m.
Re: Internal orbits	Mr. Eez	12/17/99 4:27 p.m.
Re: Internal orbits	MacGuyver	12/17/99 4:49 p.m.
Re: Internal orbits	Mark Levin	12/17/99 5:02 p.m.
Re: Internal orbits	SiliconDream =PN=	12/17/99 9:42 p.m.
Uses for the Halo's axis...	Noctavis =PN=	12/20/99 3:31 p.m.
Stable Orbits (again)	Butcher	12/21/99 1:36 a.m.
Placing a satellite in the center of the Halo	Noctavis =PN=	12/21/99 10:35 a.m.
Re: Placing a satellite in the center of the Halo	Butcher	12/21/99 2:33 p.m.
Unstable orbits... Why use a halo orbit?	Noctavis =PN=	12/21/99 6:31 p.m.
Tides on the Halo	Butcher	12/21/99 7:03 p.m.
Re: Tides on the Halo	Someguy	12/21/99 8:00 p.m.
Re: Tides on the Halo	Butcher	12/21/99 9:35 p.m.
Re: soell	•Mimer	12/25/99 3:55 p.m.
Re: soell	Matt	12/27/99 11:53 a.m.
Re: soell	Daft Shadow =PN=	12/27/99 4:11 p.m.
Re: soell	Bachus	12/27/99 6:50 p.m.
Re: Unstable orbits... Why use a halo orbit?	SiliconDream =PN=	12/21/99 11:40 p.m.
Re: Internal orbits	Nathan	12/20/99 4:37 a.m.
Re: Rotations	Forensic	12/20/99 11:58 a.m.
Re: Rotations	SiliconDream =PN=	12/20/99 2:21 p.m.
Re: Rotations	btrinen	12/20/99 2:53 p.m.
Gravity	SyberSmoke	12/20/99 3:09 p.m.
Re: Gravity	SiliconDream =PN=	12/21/99 11:00 p.m.
Re: Rotations	Noctavis =PN=	12/20/99 3:11 p.m.
Re: Rotations	Aiden	12/20/99 8:08 p.m.
Spin that ring	L. Tankersley ("Cap'n Carnage")	12/20/99 5:12 p.m.
Re: Spin that ring	Dispatcher	12/20/99 9:43 p.m.
Re: Spin that ring	L. Tankersley ("Cap'n Carnage")	12/21/99 10:25 a.m.
Re: Spin that ring	Dispatcher	12/21/99 11:10 p.m.
L1? or L4-5?	Oddot	12/22/99 10:24 a.m.
Re: L1? or L4-5?	L. Tankersley ("Cap'n Carnage")	12/22/99 2:54 p.m.
Q: How do you spin the Halo?	Ironfist [CMG]	12/20/99 5:41 p.m.
Re: Internal orbits	Chris Huff	12/20/99 6:59 p.m.
Re: Internal orbits	Ringdude	12/20/99 7:18 p.m.
Re: Internal orbits	SiliconDream =PN=	12/21/99 11:06 p.m.
Re: Internal orbits	Someguy	12/21/99 11:11 p.m.
Re: Internal orbits	SiliconDream =PN=	12/22/99 4:06 a.m.
Re: Internal orbits	Thomas Magle Brodersen	12/21/99 3:06 a.m.