Tidally locked worlds
- Thread starter Gruffty
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Gruffty
SOC-14 1K
Bodies Orbiting M V Stars Rules
Solid Planets
"A solid planet orbiting an M V star (with a mass of less than 0.7 sol) will be tidally locked to its star if the planet's orbit is within the M V star's habital zone. Such a tidally locked world will not have any moons in orbit."
Gas Giants
"A gas giant orbiting an M V star (with a mass of less than 0.7 sol) within that star's habitable zone will rotate around its axis. Such a gas giant will not have any moons in orbit."
Asteroid/Planetoid Belts
"An asteroid/planetoid belt orbiting an M V star (with a mass of less than 0.7 sol) within that star's habitable zone will rotate around the M V star."
I left out the bit about the appearance of the asteroid belt around the star cos I couldn't figure out a way to word it properly.
Solid Planets
"A solid planet orbiting an M V star (with a mass of less than 0.7 sol) will be tidally locked to its star if the planet's orbit is within the M V star's habital zone. Such a tidally locked world will not have any moons in orbit."
Gas Giants
"A gas giant orbiting an M V star (with a mass of less than 0.7 sol) within that star's habitable zone will rotate around its axis. Such a gas giant will not have any moons in orbit."
Asteroid/Planetoid Belts
"An asteroid/planetoid belt orbiting an M V star (with a mass of less than 0.7 sol) within that star's habitable zone will rotate around the M V star."
I left out the bit about the appearance of the asteroid belt around the star cos I couldn't figure out a way to word it properly.
T
TempMal
Guest
Er, this is a bit self-explanatory isn't it? what else is it going to rotate around?
Gruffty
SOC-14 1K
Er, this is a bit self-explanatory isn't it? what else is it going to rotate around?
</font>[/QUOTE]<Gruffty gives TempMal "The Bird"> My finger, smartass
Yeah, OK, so I goofed. Not for the first time, eh?
Asteroid/Planetoid Belts
"An asteroid/planetoid belt orbiting an M V star (with a mass of less than 0.7 sol) within that star's habitable zone will will not be subject to tidal locking."
T
TempMal
Guest
Well really, I don't think asteroid/planetoid belts need qualifiers like this: The individual asteroids in the belt are going to orbit the star in as much time as their precise orbital distance dictates. The larger bodies in the belt are probably going to be tidelocked, but I'd imagine that the smaller bodies (less than 1 km radius?) would be more likely to be independently rotating. It's pot luck really - they all want to be pointing towards the sun (literally - tidelocking orients the long-axis of an irregular object toward the primary) but they're also smacking into eachother every now and then and knocking chips off eachother and being set tumbling because of it.
If you're going to specify anything about belts, you might just want to say that most of the asteroid orbits are going to be in the equatorial plane of the star (i.e. the ecliptic of the system), many of the major asteroids aren't likely to be in eccentric orbits, and there's probably noticeable gaps in the belt due to the influence of planets beyond the outer edge. Then again, that might be too much detail to mention .
If you're going to specify anything about belts, you might just want to say that most of the asteroid orbits are going to be in the equatorial plane of the star (i.e. the ecliptic of the system), many of the major asteroids aren't likely to be in eccentric orbits, and there's probably noticeable gaps in the belt due to the influence of planets beyond the outer edge. Then again, that might be too much detail to mention
.This is another crucial topic for referees; the subject of tidal locking is both fascinating and very important IMO. I found this on the www:
http://www.geocities.com/Area51/Chamber/2838/wbcookbook2.pdf
Included in the file is this bit of info:
Tidal lock limit in AU = 0.0483 (T * M squared / density of planet)1/6
The density of the planet is in kg/cubic meters and the parenthetical equation is to the 1/6 power.
T = age in years of the system
M = mass of the star in solar masses
On the surface (and with my limited experience in this science) this appears plausible. But any critique by those more knowledgable would be greatly welcomed.
http://www.geocities.com/Area51/Chamber/2838/wbcookbook2.pdf
Included in the file is this bit of info:
Tidal lock limit in AU = 0.0483 (T * M squared / density of planet)1/6
The density of the planet is in kg/cubic meters and the parenthetical equation is to the 1/6 power.
T = age in years of the system
M = mass of the star in solar masses
On the surface (and with my limited experience in this science) this appears plausible. But any critique by those more knowledgable would be greatly welcomed.
T
TempMal
Guest
That tidelock equation is definitely a fudge - the obvious factor they miss out is the age of the system (whether a planet is tidelocked depends on when in the system's history you find it). Another factor they miss is the initial rotation period of the planet (which affects how long it takes to get to a tidelocked state). Other factors include the moment of inertia of the planet and the bulk rigidity of the planet too.
Plankowner
SOC-13
How about this Q&D rule?
If it is in the Inner Zone and not a GG it is Tidally Locked, or in some kind of stellar resonance (like Mercury) that might as well be tidal. Venus has a rotation that is actually longer than it's year, but I would call that Tidally Locked for any gaming purposes.
If it is in the Habitable Zone, it is Tidally Locked on 2d6 roll GREATER THAN the size of the world. Thus big worlds, with lots of angular momentum are harder to tidally lock, but small worlds are easier.
In the Outer Zone, no worlds are Tidally Locked.
I would use the 2d6 to roll GREATER THAN the size for all moons as well. This gives the larger, habitable sized moons a chance to have a "normal" rotation, but most would still be tidally locked like we see in the Solar System.
Rough, sure, but I think it would work for gaming purposes.
[Edited to fix typo]
If it is in the Inner Zone and not a GG it is Tidally Locked, or in some kind of stellar resonance (like Mercury) that might as well be tidal. Venus has a rotation that is actually longer than it's year, but I would call that Tidally Locked for any gaming purposes.
If it is in the Habitable Zone, it is Tidally Locked on 2d6 roll GREATER THAN the size of the world. Thus big worlds, with lots of angular momentum are harder to tidally lock, but small worlds are easier.
In the Outer Zone, no worlds are Tidally Locked.
I would use the 2d6 to roll GREATER THAN the size for all moons as well. This gives the larger, habitable sized moons a chance to have a "normal" rotation, but most would still be tidally locked like we see in the Solar System.
Rough, sure, but I think it would work for gaming purposes.
[Edited to fix typo]
Welcome Plankowner,
Do you mean 2D6 over size? This would make it harder to tidally lock large worlds.
I very much like this mechanic and will adopt it if you don't mind.
It also plays well into the atmosphere thread as a tidally locked world might have less of an atmosphere from the constant heating of one side thereby increasing loss. Maybe -1 modifier to atmosphere if tidally locked.
Do you mean 2D6 over size? This would make it harder to tidally lock large worlds.
I very much like this mechanic and will adopt it if you don't mind.
It also plays well into the atmosphere thread as a tidally locked world might have less of an atmosphere from the constant heating of one side thereby increasing loss. Maybe -1 modifier to atmosphere if tidally locked.
Plankowner
SOC-13
Ptah, I meant 2d6 OVER size, as you said. I knew what I was thinking but didn't word it right. Feel free to use it, I have no pride of ownership. Anything I say here is fair game and I treat everyone else's suggestions the same. If I wanted something copyrighted, it wouldn't be here.
I have used it for a long time and it seems to work without too many gotcha's. Of course you will get the prime 867 world that is tidally locked occasionally, but that is what is fun about this game.
The -1 DM might work. I might suggest a DM -2 since the atmospheric densities work in pairs on the standard atmosphere table (2&3, 4&5, 6&7, 8&9). Therefore a tidally locked world would TEND to have a thinner atmosphere than an regularly rotating world.
I have used it for a long time and it seems to work without too many gotcha's. Of course you will get the prime 867 world that is tidally locked occasionally, but that is what is fun about this game.
The -1 DM might work. I might suggest a DM -2 since the atmospheric densities work in pairs on the standard atmosphere table (2&3, 4&5, 6&7, 8&9). Therefore a tidally locked world would TEND to have a thinner atmosphere than an regularly rotating world.
