Re: ODE's again (sorry)

["Sam Halliday" <plendily at hotmail dot com>]

i thank you for your comments

yes the equation of motion is incorrect, but this is only because i have 
trimmed it down to the bare essentials for posting, the problem is however 
in units, not in dimensions, it is a very simple 3 dimensional orbits 
calculation.... i have the euler approach workign perfectly as it should, 
although requires a small step size and is unstable at large age 
projections.

i am not very familiar with the algorithms available to me except euler and 
runge-kutta, i felt runge-kutta was appropriate since i am solving 3 2nd 
order equations and require to conserve the energy of the system, but you 
are right this is essentially a 6 first order equation problem and im sure 
it can be solved in a much better way, but my reason for posting was not so 
much to ask for numerical advice... but instead check if this was a possible 
bug in the RK algorithm, which i believe it is... as my method (no matter 
how inefficient) should work.

i dont have a clue how to set this RK up in 6 dimensions, the whole jacobian 
declaration was quite confusing, i never heard of a need for a jacobian and 
yet this algorithm needs it.

Sam
---
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