Question A question from the Ducan Sharpe's "deep space manual"

[Lele81]

I don't know if all of you know this deep space and transX manual (it's very good!!!), however, since I'm not english, I have a "translation doubt"....I can't understand what a particular phrase means, can anyone help me with other words?

It is that, from the manual, page 4:
The orbits aren't coplanar.
This one causes problems. The reason why it does can be seen by looking at a Hohmann transfer from a different angle. If you start from a given planet at a given time, all orbits of a certain size that start from there converge on the same spot 180' around from the start.

I don't understand what the red part means...I know what it means "not coplanar" however!
Thanks!!!

 

[Tommy]

"Not Coplanar" the two objects aren't on the same orbital plane. If two objects "start" at the same place in different directions (on different planes), then that point will be an intersection, AKA a node. Since there are two nodes, and the nodes are always 180 degrees (the opposite side of the orbit) apart, if the two objects have the same size orbit (same diameter, ecc, period, etc) they will intersect again at that second node.

Hope that makes it slightly clearer!

 

[TSPenguin]

This is also explained beautifully in Orbital Operations.

 

[Sam]

If you start from a given planet at a given time, all orbits of a certain size that start from there converge on the same spot 180' around from the start.

I don't understand what the red part means

Think of it this way. Suppose your spacecraft was hanging motionless over the North Pole, and the Earth wasn't turning. You could put yourself into orbit by moving in any direction, which would start you moving along some line of longitude. And you could choose your orbit so that you passed over London, Moscow, or any other city you liked. But no matter which line of longitude you chose to be your orbital path, at the other side of the Earth you'd still end up over the South Pole.

SAM

 

[Lele81]

Think of it this way. Suppose your spacecraft was hanging motionless over the North Pole, and the Earth wasn't turning. You could put yourself into orbit by moving in any direction, which would start you moving along some line of longitude. And you could choose your orbit so that you passed over London, Moscow, or any other city you liked. But no matter which line of longitude you chose to be your orbital path, at the other side of the Earth you'd still end up over the South Pole.

SAM

Thanks to all of you, however that is, at last, very clear to me!!!