Advanced Question IMFD Planet Approach to ISS

[PaulG]

If I'm approaching Earth from another planet, and I want to change my inclination to match the ISS, how do I do that in IMFD?

Here is what I'm doing: When close to earth I change to the planet approach program. I set Ref: Earth, Target: ISS, Source: Self, and set the altitude (average of the ISS PeA, ApA), and then what do I put for EqI?

Thanks,
Paul

 

[Jarvitä]

EqI - orbital inclination in the equatorial frame. You can see it in the Orbit MFD, just set your reference to earth, target the ISS and set the frame to equatorial.

 

[PaulG]

Thats what I thought. In Orbit MFD, I set Orbit: Earth, and Target: ISS, and switch to Equ mode to get the inclination: 55.30 degress. I set EqI to that, but the ecliptic inclination is WAY off....Ship Ecl Inc: 32.96, Iss Ecl Inc: 66.18. So, obviously my LANs are way off.

How do I correct for this enroute to Earth?

Thanks.

 

[Jarvitä]

Thats what I thought. In Orbit MFD, I set Orbit: Earth, and Target: ISS, and switch to Equ mode to get the inclination: 55.30 degress. I set EqI to that, but the ecliptic inclination is WAY off....Ship Ecl Inc: 32.96, Iss Ecl Inc: 66.18. So, obviously my LANs are way off.

How do I correct for this enroute to Earth?

Thanks.

A minor velocity correction to alter your arrival time?

 

[PaulG]

Yes, but how do I calculate that? Can it be done with IMFD?

 

[HiPotOk1978]

never tried to do plane allignment with IMFD so I am not sure if it has the ability to do so. when I know I am going to be approaching a planet or moon and I am going to be needed a high inc orbit, I will make sure my appoach is from a high altitude from the surface with enough time in that high orbit so I can intersect the orbit I am trying to sync with then use allign planes. I know this procedure is prob not exactly what you want but it is tried and true for me many times over.

Plane change burns from high orbits are many times over more efficient than from lower orbits. The reason for this is as you orbit an object at higher and higher altitudes, your speed is lowered. Plane changing is best done at VERY low speeds. The same principle applies in aircraft.

 

[Tommy]

Disregard the comment that was here - posted in wrong tab.

Eggnog + posting = bad!

 

[shanbe]

Well, from what I can imagine, setting EqI will not help you in this situation. I think that two objects orbiting Earth with the same equatorial inclination can have huge relative inclination (due to different longitude of ascending node). In fact, entering the same orbit as the target has without any plane change manouver is almost impossible.

The method described by HiPotOk1978 sounds good to me. Arrive in high altitude, then align planes and then perform final approach. I also made some experiments with a IMFD course program to solve this in one step, but without any good results. Well, I'm IMFD noob, so maybe there is some way to do it

 

[Arkalius]

As others have mentioned, while IMFD can help you insert at a particular equatorial inclination, there is no way to really control your LAN independently of the inclination during approach. The only real way to do that is change your arrival time so that your LAN is equal to your target's when you arrive. The closer you are to the planet the harder it is to alter your arrival time, but you need to be fairly close to be able to effectively modify your inclination. It's a tough challenge and I'm not sure there's an MFD that can help you do this. You'll likely have to stick with the plane change after arriving method.