### Author Topic: Q&A Based orbit raising with electric propulsion  (Read 920 times)

#### dinos55

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##### Q&A Based orbit raising with electric propulsion
« on: 11/06/2017 09:55 AM »
can someone tell me how to calculate the deltavs and the dry mass of a satellite for ab orbit raising from leo to geo with electric propulsion?

#### envy887

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##### Re: Q&A Based orbit raising with electric propulsion
« Reply #1 on: 11/06/2017 05:42 PM »
can someone tell me how to calculate the deltavs and the dry mass of a satellite for ab orbit raising from leo to geo with electric propulsion?

Wiki has delta v budgets for that: 6000 m/s. https://en.wikipedia.org/wiki/Delta-v_budget#Earth.E2.80.93Moon_space.E2.80.94low_thrust

If you know the exhaust velocity of your thruster, plug both those into a handy delta-v calculator: http://www.strout.net/info/science/delta-v/

#### dinos55

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##### Re: Q&A Based orbit raising with electric propulsion
« Reply #2 on: 11/06/2017 06:23 PM »
thank you for your reply..but what I am really asking is how to calculate these values using electric propulsion. how to calculate deltav and the dry mass? how many revolutions does the s/c make until final orbit?

#### brickmack

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##### Re: Q&A Based orbit raising with electric propulsion
« Reply #3 on: 11/06/2017 07:59 PM »
Theres not an analytical solution for calculating non-impulsive transfers, you'll have to run an actual simulation of some sort

#### dinos55

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##### Re: Q&A Based orbit raising with electric propulsion
« Reply #4 on: 11/08/2017 08:32 AM »
do you know any software for running this kind of simulations?

#### brickmack

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##### Re: Q&A Based orbit raising with electric propulsion
« Reply #5 on: 11/09/2017 09:25 PM »
Could try some of the stuff listed here https://space.stackexchange.com/questions/646/what-are-the-choices-today-for-orbital-mechanics-simulation-software

I'm writing my own right now, but it still has no user interface

#### dinos55

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##### Re: Q&A Based orbit raising with electric propulsion
« Reply #6 on: 11/12/2017 03:43 PM »
@brickmack thank you a lot!! I would like to try and write my own algorithm..can you give me a hint on how to start??

#### brickmack

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##### Re: Q&A Based orbit raising with electric propulsion
« Reply #7 on: 11/12/2017 05:00 PM »
For an n-body simulation, Newtons Law of Universal Gravitation is the main thing. You'll be doing all the actual simulation math using orbital state vectors, and then convert that to Keplerian elements or whatever other human-readable format you want. This page has the equations you'll need. Except that page assumes only a 2 dimensional orbit, but adding a third dimension should be fairly self-explanatory. It also assumes you're only simulating one body orbiting one other body (one being of negligible mass). So, firstly, you'll want to apply the force (not the acceleration) in opposite directions on both objects.

Secondly, you're probably wanting to simulate the interactions of more than two objects, so for every object you'll want to apply NLUG with every other object in the simulation (I recommend pre-calculating an array containing every valid pair of object interactions, eg {[earth:moon], [earth:sun], [earth:satellite], [moon:sun], [moon:satellite], [sun:satellite]}. With n objects, you'll have nC2 interactions, presuming you don't use any limits to avoid having to calculate negligible influences, eg plutos gravity on a satellite in LEO). The way you'll want to do this is, every timestep of the simulation, calculate the force imparted on every object by every other object, add up the force vectors applied to each object, and then at the next tick (not before), calculate the total change in velocity and position from that net force vector and apply it.

That gets you the orbital mechanics part. You'll probably also want to be able to maneuver your spacecraft. The method here is broadly similar. You'll define a unit vector in the direction you want to thrust towards, and then multiply that unit vector by the thrust your engine produces in Newtons. As before, you'll add this force vector to the net force vector from before, and calculate acceleration, velocity, and position from that on the next tick. Also, because engines consume propellant, subtract the propellant consumed each tick from the vehicle wet mass (calculate this propellant consumption using the ISP formula).

I can post my code if you're interested (it uses a few non-standard Java libraries for display though)

#### Proponent

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##### Re: Q&A Based orbit raising with electric propulsion
« Reply #8 on: 11/12/2017 08:36 PM »
If you're building your own, I suggest starting with something simple, namely just one body.  Play with that, check it against cases you can solve exactly to make sure it's accurate, and get a feel for how it works.  Then start elaborating the model.

#### envy887

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##### Re: Q&A Based orbit raising with electric propulsion
« Reply #9 on: 11/12/2017 11:36 PM »
If you are only concerned about raising an orbit from LEO to GEO, you can get very high accuracy while modeling only the Earth and the satellite.

#### deruch

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##### Re: Q&A Based orbit raising with electric propulsion
« Reply #10 on: 11/13/2017 02:41 AM »
The following paper (sorry, I haven't read it) will likely give you some idea of the considerations and/or by looking up the cited references you'll be on your way to answering your question.

"ADVANTAGES OF A CONTINUOUS THRUST STRATEGY FROM A GEOSYNCHRONOUS TRANSFER ORBIT, USING HIGH SPECIFIC IMPULSE THRUSTERS"

http://issfd.org/ISSFD_1999/pdf/OC1_1.pdf