May 5th, 2017, 01:37 AM  #1 
Senior Member Joined: Apr 2014 From: UK Posts: 777 Thanks: 292  Orbits
I think it is possible to orbit the Earth such that the position is always directly between the Earth and Sol. Is this correct, and is it technically orbiting the Earth or the sun? How might I work out the distance from Earth of such an orbit (assuming it exists)? 
May 5th, 2017, 02:07 AM  #2  
Senior Member Joined: Apr 2014 From: Glasgow Posts: 2,049 Thanks: 680 Math Focus: Physics, mathematical modelling, numerical and computational solutions  Quote:
Quote:
Quote:
$\displaystyle F_{Earth} = G\frac{M_{test} M_{Earth}}{r^2}$ $\displaystyle F_{Sun} = G\frac{M_{test} M_{Sun}}{(d  r)^2}$ where G is the universal gravitational constant, r is the distance the test mass is from the Earth (in metres) and d is the EarthSun distance (in m) A more difficult, detailed calculation can be done using Lagrangian mechanics and then you'll find many more Lagrange points https://map.gsfc.nasa.gov/ContentMedia/lagrange.pdf  
May 5th, 2017, 02:42 AM  #3 
Senior Member Joined: Apr 2014 From: UK Posts: 777 Thanks: 292 
Interesting, I didn't understand a lot of it, but it seems L1, which is what I was aiming for, isn't stable, so it's either L4 or L5, I just need to work out how to get there 
May 8th, 2017, 01:25 AM  #4 
Senior Member Joined: Apr 2014 From: Glasgow Posts: 2,049 Thanks: 680 Math Focus: Physics, mathematical modelling, numerical and computational solutions  Yes, L1 is a position of unstable equilibrium and any satellite placed there would need some sort of rocket to keep it there, adjusting its thrust in order to counteract any perturbations.

May 8th, 2017, 07:29 AM  #5 
Senior Member Joined: Apr 2014 From: UK Posts: 777 Thanks: 292 
I doubt we could harvest enough power to keep ourselves stable at L1. Radiation is also a bit of an issue. Looks like I'll have to stay down here a bit longer 
May 9th, 2017, 01:11 AM  #6 
Senior Member Joined: Apr 2014 From: Glasgow Posts: 2,049 Thanks: 680 Math Focus: Physics, mathematical modelling, numerical and computational solutions  

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