Molniya orbit and KSP

[Pawelk198604]

I read very interesting article about Molniya orbit, it useful for polar region comsat

I was wondering does anyone ever put satellite on Kerbin Molniya orbit. I several time put satellite on Kerbin geosynchronous orbit, but never tried Molniya.

[FITorion]

Could you describe it for those of us who have never heard the term?

[molunbun]

When I failed to circularize an orbit

[Ralathon]

Could you describe it for those of us who have never heard the term?

A Molniya orbit is a highly eccentric orbit with an orbital period some fraction of the parent's rotational period. Due to the high eccentricity it spends much of its time over 1 specific area of land. It's useful for communications and spying on others. For example, Russians used Molniya orbits with a period of 12 hours and the apoapsis above the US during the cold war. That way they only needed 2 sats or so to make sure there was always a spysat above USA soil.

[Iron4venger]

youre welcome

the beauty of molniya is that you need to recalculate everything for any point you want to cover down there.

Edited November 1, 2013 by Iron4venger

[Kasuha]

How to make Molniya orbit:

1/ make a 70 km orbit (or 75 for some safety margin).

2/ when you are at the exactly opposite side of Kerbin than the place you want to "spy on", start burning prograde

3/ click on PA and AP to see the numbers. Notice that beside the height, there's also the time to reach it

4/ continue burning till the difference between the two times is exactly 3 hours

5/ if you feel like it, adjust your inclination. Take care to not break orbital period, use combination of normal and retrograde. Best done with a maneuver node.

[Pawelk198604]

Thanks :-)

[katateochi]

Now the first thing I do in a fresh (sandbox) save is to put 4 remote tech satellites in Molniya orbits round kerbin.

When I started out I put these satellites in almost circular orbits and spaced them out on the same orbit to give total planet coverage. But it was impossible to get each ones orbit exactly equal to the others, there was always a few m difference. That meant over time their relative positions would shift and periodically (after most other missions) I'd have to adjust them or have coms blackouts (resulting in the loss of a number of probes).

I asked how others kept satellites in relative positions and the helpful folk here pointed me towards molniya orbits. I don't do the maths so they are probably not strict molniya orbits but they get the job done; unbroken coverage round kerbin,

This was my setup in 0.21; 4 in molniya/elliptical orbits and 2 further out (which are longer range relays) on circular orbits.

First pic is just after setting them up so they are similar positions in their orbits. 2nd is some time later and their relative positions have changed, but that doesn't matter anymore. (2nd pic also shows a surface relay station on Mun's north pole being used).

[EliteShadowLeo]

This is giving me some very good ideas, I haven't particularly paid much attention to satellites in 0.22, Thanks!

[jduchock]

anyone know what the inclination for an optimum Molniya orbit over KSP? I know earth is something like 64 degrees to avoid earth gravity influence, but not sure how it works out for Kerbin...

[Lexif]

anyone know what the inclination for an optimum Molniya orbit over KSP? I know earth is something like 64 degrees to avoid earth gravity influence, but not sure how it works out for Kerbin...

It doesn't matter as Kerbin is, unlike earth, a perfect sphere when it comes to gravity.

Edited November 1, 2013 by Lexif
clarified