Orbit Questions

[OrbiterAddict]

Hello Orbinauts!
It may be my first post in the forums, but I've had Orbiter installed for quite some time (although I started flying seriously since I discovered the "Go Play In Space" guide).
Now, I have some math-related questions, some of them might be or sound silly. I'll start with a image:

1) How is an Orbit defined? Propably with the RInc and either the distance from the Eq @ PM or the distance from the PM @ Eq. (see the image above). And the Periapsis-apoapsis of course [Answered]

2) What is the relation between the Rinc, the distance from the Eq @ PM and the distance from the PM @ Eq? Logically, if you know 2 of those you can calculate the other one... [Unanswered, but propably unnecessary question]

3) We have a satellite in orbit, how can we know the geographical coordinates of its position at a specific point? [???]
And how is a point in an orbit defined? [Answered]

4) How much NORM+/NORM- thrust do I need to make the satellite pass over my hometown if I know it's geographical coordinates? [Answered]

I want to learn more about his kind of stuff! What are the terms to google? Any books you can recommend?

Thank you in advance!

 

[dgatsoulis]

Γεια σου, OrbiterAddict.
It's a pleasure to greet a compatriot here.

to the forums.

Congrats on starting with Go Play In Space. That's a must for every beginner Orbinaut.

As for your questions, I suggest taking a look at this page.

Have fun, happy orbiting.

 

[Quick_Nick]

1) In real life, orbit is defined by Two-Line Elements. Orbiter can use similar elements or often just position and velocity.
See: http://www.orbiterwiki.org/wiki/Orbital_elements

2) I'm not sure, but normally we don't use these terms. We use the Longitude of Ascending Node, and often in relation to the ecliptic plane, not the equatorial plane.

4) Try using Align Planes MFD. One of the options has you put in the desired Inclination and Longitude of Ascending Node. Set the inclination to the latitude of the location and set the LAN to the longitude of your target minus 45(?) degrees. You'll pass over the target at the farthest north (or south) part of your orbit.

EDIT: In 4, you may have to adjust the inclination to be in reference to the ecliptic. And that 45 may or may not be correct.

 

[Izack]

Rinc to what? Rinc is Relative Inclination, which requires a reference to another orbiting object. If you simply mean inclination, it is not taken from the object's location, but from its orbital plane, as seen in this image:

In this case, the plane of reference is either the Plane of the Ecliptic (plane of the Earth's orbit around the Sun), or the local Equatorial plane (the plane of the Earth's rotation, ~23 degrees off the ecliptic.)


Sorry if I'm misunderstanding your question.

 

[OrbiterAddict]

Γεια σου, OrbiterAddict.
It's a pleasure to greet a compatriot here.

to the forums.

Congrats on starting with Go Play In Space. That's a must for every beginner Orbinaut.

As for your questions, I suggest taking a look at this page.

Have fun, happy orbiting.

Ευχαριστώ
And that page looks really interesting:

To mathematically describe an orbit one must define six quantities, called orbital elements. They are

* Semi-Major Axis, a
* Eccentricity, e
* Inclination, i
* Argument of Periapsis,
* Time of Periapsis Passage, T
* Longitude of Ascending Node,

I will study it tomorrow, it will propably answer some more questions.

1) In real life, orbit is defined by Two-Line Elements.
See: http://www.orbiterwiki.org/wiki/Orbital_elements

Exactly what I quoted above

2) I'm not sure, but normally we don't use these terms. We use the Longitude of Ascending Node, and often in relation to the ecliptic plane, not the equatorial plane.

Obviously making questions based on my assumptions wasn't a good idea. :lol:

4) Try using Align Planes MFD. One of the options has you put in the desired Inclination and Longitude of Ascending Node. Set the inclination to the latitude of the location and set the LAN to the longitude of your target minus 45(?) degrees. You'll pass over the target at the farthest north (or south) part of your orbit.

Never noticed that option... But still, I am asking how to do that on paper, without any MFDs or software.

Rinc to what? Rinc is Relative Inclination, which requires a reference to another orbiting object. If you simply mean inclination, it is not taken from the object's location, but from its orbital plane, as seen in this image:

I thought Rinc was the relative inclination to the equatorial plane... Anyway, yes, that's what I mean. And from the image I guess that to define a point in an Orbit we use a Reference Direction?

Thank you everyone, keep it coming if you have anything to add. I think 3) is still unanswered

 

[Quick_Nick]

For calculating on paper: http://www.braeunig.us/space/orbmech.htm#maneuver
Scroll down to the Plane Change section. Equations in there will tell you how much dV you need as well as when to perform the maneuver depending on Inc and LAN.

 

[tblaxland]

2) What is the relation between the Rinc, the distance from the Eq @ PM and the distance from the PM @ Eq? Logically, if you know 2 of those you can calculate the other one... [Unanswered, but propably unnecessary question]

It is unnecessary for defining the orbit according to the conventional elements (as you've seen from the other posts above) but its an interesting mathematical problem in its own right. You can use spherical trigonometry to solve it and specifically you need Napier's rules for right spherical triangles. There is a good page on it here: http://www.rwgrayprojects.com/rbfnotes/trig/strig/strig.html