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Useful formulae and constants (IE may not work) (Read 9221 times)
abyssoft
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Useful formulae and constants (IE may not work)
01/15/12 at 11:53:05
 
Angular Frequency  
 

ω=2π/T=2πf=|v|/|r|  
 
ω is the angular frequency or angular speed (radians per second)
T is the period (seconds)
f is the ordinary frequency (hertz,sometimes symbolised with ν)
v is the tangential velocity of a point about the axis of rotation (meters per second)
r is the radius of rotation (meters)
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« Last Edit: 03/12/12 at 16:44:19 by abyssoft »  
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Re: Useful formulae and constants
Reply #1 - 01/15/12 at 12:10:59
 
Oblateness Constant (simple)              
 

q ≡  (aω^2)/g=aω^2  a^2/GM=(a^3 ω^2)/GM
 
a is equatorial radius (meters)
ω is the angular frequency or angular speed (radians per second)
g is gravitational acceleration(meters per second)
G is the graviational constant 6.67384×10^(-11)  m^3 kg^(-1) s^(-2)
M is mass of body (kilograms)
This does not take into account differentiation.  To fudge this on can take M and multiply
against either a random number between 0.8 and 1.2 or mulitply against a system wide
value to represent general differentiation.
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« Last Edit: 03/12/12 at 16:43:34 by abyssoft »  
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Re: Useful formulae and constants
Reply #2 - 01/15/12 at 16:20:45
 
Roche limit advanced                  
 

d≈2.423R(ρMm)^(1/3)·{[(1+m/3M)+1/3q(1+m/M)]/(1-q)}^(1/3)[/size]
 
d is distance from center of primary
ρ_M  is density of primary
ρ_m  is density of satillite
M is mass in of primary
m is mass in of satillite
q is the oblateness constant (also listed as c/R)
[/size]
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« Last Edit: 03/12/12 at 16:42:23 by abyssoft »  
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Re: Useful formulae and constants
Reply #3 - 01/15/12 at 19:17:54
 
Orbital Period                  
 

P=2π√(a^3/G(M+m))
 
P is period of orbit (seconds)
a is separation distance (meters)
M is mass in of primary
m is mass in of satillite
G is the graviational constant 6.67384×10^(-11)  m^3 kg^(-1) s^(-2)
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« Last Edit: 03/12/12 at 16:41:39 by abyssoft »  
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Re: Useful formulae and constants
Reply #4 - 01/15/12 at 19:20:07
 
Minimum Rotational Period      
 

P=2π√(r^3/GM)
 
P is period of orbit (seconds)
r is equatorial radius (meters)
M is mass of body (kilograms)
G is the gravitational constant 6.67384x10-11 m^3 kg^(-1) s^(-2)
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Re: Useful formulae and constants
Reply #5 - 01/15/12 at 22:54:33
 
Synchronous Orbit                  
 

r=(GM/ω^2)^(1/3)
 
M is mass of body (kilograms)
G is the gravitational constant 6.67384x10-11 m^3 kg^(-1) s^(-2)  
r is the elevation from the center of the body (meters)
ω is the angular frequency or angular speed radians per second
 
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« Last Edit: 03/12/12 at 16:40:10 by abyssoft »  
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Re: Useful formulae and constants
Reply #6 - 01/15/12 at 22:55:08
 
Synchronous Orbit Velocity      
 

v=ωr
 
v is the velocity of the synchronous orbit (meters per second)
r is the elevation from the center of the body (meters)
ω is the angular frequency or angular speed (radians per second)
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« Last Edit: 03/12/12 at 16:39:18 by abyssoft »  
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Re: Useful formulae and constants (IE may not work
Reply #7 - 01/16/12 at 20:13:35
 
Effective Planet Temperature      
 

Teff=((L☉ (1-A))/(16πσa^2 ))^(1/4)
 
Teff  is the effective surface temperature not accounting for greenhouse effect (kelvin)
L☉ is the luminosity in solar units and must be converted to watts L☉∙3.846×10^26  W
A is the geometric albedo (earth = 0.367)
σ is the Stefan-Boltzmann constant 5.670400×10^(-8) J s^(-1) m^(-2) K^(-4)
a is the semi-major axis(meters)
 
To get minimum Teff and maximum Teff adjust to perihelion and apohelion
 
This does not take into account any greenhouse effect factor,H,to add in H use the following
modification to the T_eff  formula
 

Twgh=Teff(1+0.15∙H/|H|∙|H|^(1/2))
 
Twgh is the temperature factoring in with the greenhouse effect
H is the Green House Factor (earth = 1).
 
It is not unusual for H to be a negative value for bodies who either have  
a highly reflective surface or a thin conductive atmosphere, Enceladus and Mars  
are prime examples.  
 
For gas planets that are in excess of 12 Mjup  black body value for
planet should be included at equatorial radius as planet will most  
likely still be radiating heat from formation.
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Re: Useful formulae and constants (IE may not work
Reply #8 - 01/16/12 at 23:10:39
 
Luminosity Mass Relationship
 

L=kM^n
 
L is the luminosity of the stellar object
k is multiplier factor
M is the mass of the stellar object in Solar masses
n is the power factor
 
k and n vary according to M
M≤0.43;k=0.23,n=2.3
M≤2.00 and M>0.43;k=1,n=4
M≤20.0 and M>2.00;k=1.5,n=3.5
M>20.0;k=1;n=4-M/(44+(M/10.25)^2 )
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« Last Edit: 03/12/12 at 17:12:42 by abyssoft »  
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Re: Useful formulae and constants (IE may not work
Reply #9 - 01/16/12 at 23:11:19
 
Volume of an oblate spheroid      
 

V=4/3 πr_e^2 r_p
 
V is the volume of the  body
r_e  is the equatorial radius
r_p  is the polar radius r_e (1-q)
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« Last Edit: 03/12/12 at 17:14:53 by abyssoft »  
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Re: Useful formulae and constants (IE may not work
Reply #10 - 01/16/12 at 23:15:29
 
Hill sphere                        
 

r_hill≈a(m/3M)^(1/3)
 
a is the semi-major axis of the orbit
M is the mass of the primary
m is the mass of the secondary
 
Maximum distance for stable retrograde orbit  
 

d=(((δ_s+φ)/2))/3 r_hill
 
Maximum distance for stable prograde orbit
 

d=φ/3 r_hill
 
d is distance to limit
δ_s  is the silver ratio 1+2^(1/2)
φ is the golden ratio (1 + 5^(1/2))/2
r_hill  is the hill sphere radius
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« Last Edit: 03/12/12 at 17:22:39 by abyssoft »  
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Re: Useful formulae and constants (IE may not work
Reply #11 - 01/17/12 at 13:58:35
 
Gravitational dominance range of a perturbing body
 
     Inner Reach                  
                                               d_inn=a((1-e)-n_inner(m/3M)^(1/3) )
 
     Outer Reach                  
                                               d_out=a((1+e)+n_outer(m/3M)^(1/3) )
 
d is the distance inward(inn) or outward(out)
a is the semi-major axis of the bodies,for the star use radius of star for outer reach
e is the eccentricity of the orbiting body,for star use eccentricity of 0
n is the scalar modifier more on this value can be found at Jones et. al. (2006)  
 
Values for n and means to calculate were refined for accuracy and better curve fitting; I was assisted by Tony on this.
 


 
M is the mass of the primary
m is the mass of the secondary
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« Last Edit: 03/12/12 at 22:35:27 by abyssoft »  
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Re: Useful formulae and constants (IE may not work
Reply #12 - 01/19/12 at 12:25:19
 
Interplanetary region can have belt and/or dwarf planet when BD_bool is true
 
     
           BD_bool = ( d_inn [outerbody] - d_out [innerbody] - d_inn [innerbody] ) > 0
 
*commentary*
Minimum mass of dwarf planet can be based on the smallest known body Saturn I (Mimas) to be in hydrostatic equilibrium with a mass of 3.75×10^19  kg. However, it may be slightly lower if composition was structurally less rigid.  
*/commentary*
 
When BD_bool is true, Maximum expanse of a belt or range for possible stable orbits of a dwarf planet
 
Expanse_middle = d_inn [outerbody]-d_out [innerbody]

Expanse_width = 1.5 (d_inn [outerbody]-d_out [innerbody]-d_inn [innerbody] )
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« Last Edit: 03/12/12 at 22:51:32 by abyssoft »  
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Re: Useful formulae and constants (IE may not work
Reply #13 - 01/19/12 at 14:53:37
 
Concerning Maximum mass of dwarf planet or intraexpanse planet
 
Stable orbits for bodies within an expanse are  
 
1) typically not in resonance with the outer planet;  
1a) in the case of those beyond the the last major planet, resonances with the planet typical ensure stability up to 1:4 1b) weaker resonances may be present but may mearly be coincidental or transient.
 
2) e is frequently a value between the e of the inner and outer planet, as outside the range can lead to overlaping gravitational dominance zones, which would lead to eventual destablization of the orbit.  
 
3) will not be stable when at the edges (+/-10%) of the expanse unless in resonance with inner planet and inner planet is significantly more massive then outer. (Empirical testing through simulations)
 
To find the maximum mass that would be stable in the system within the selected parameters use one the following.
 
The values for a, e, and either d_inn or d_out must be selected/determined before solving for m.  
 

m = -(3( a * e - a + d_inn )^3)/(a^3 n^3 M)  

m = -(3( a * e + a - d_out )^3)/(a^3 n^3 M)
 
refer to the variables in Gravitational dominance range of a perturbing body for explinations
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« Last Edit: 03/12/12 at 22:56:02 by abyssoft »  
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Re: Useful formulae and constants (IE may not work
Reply #14 - 01/19/12 at 14:54:49
 
Kirkwood gaps,  
Kirkwood peaks
 
Continued analysis,experimentation, along with the following paper I found earlier today (http://www.fisica.edu.uy/~gallardo/marte12/mars1to2.html ) has yielded that resonances with the inner planet strengthen the population of SSSB; leading to Kirkwood peaks.
 
There also seems to be some impact by the resonances with both the inner reach and the outer reaches.  
I'm investigating the resonances with the Hill sphere ranges.
 
Still working on these will update as I get these nailed down a bit better, or discover more.  
 
The deeper analysis is taking quite a bit of time as I run both sims and statistical sequences.
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