Tangential Transfer for LEO?

[blane]

Hi,

I'm in the process of trying different methods to rendevouz with a station or ship in LEO. Align Planes + Sync Orbit is fine... But I think it should be possible with IMFD as well?

I would believe tangential transfer suits my needs: Usually I am in a lower circular orbit than my target, So I want to change my orbit in a way that I have a tangential (single point) intersection at my Apoapsis.

But if I use Tangential Transfer for -- let's say, meet ISS from a 200km Orbit -- it frequently jumps around wildly. I cannot adjust anything there...

Anyone have some hints for me, for an easy IMFD approach to ISS (or any othe object in LEO/LLO/LMO)?

 

[tblaxland]

I haven't used IMFD tangential transfer for this purpose before. I have used its Target program with success, though. I generally use a combination of Align Planes + Sync Orbit + [ame="http://www.orbithangar.com/searchid.php?ID=1199"]Rendezvous MFD[/ame].

 

[blane]

Uh.. RendevouzMFD *shudder*

This thing still scares me. I read the readme... but uh... whenever I click around there ingame I finally decide to use another MFD

 

[Andy44]

Well, all of Orbiter scared me when I first DL'd it, but look at me now! Rendezvous MFD isn't so hard.

 

[Zatnikitelman]

The key with Rendezvous is to "clear the graph" as I call it. I always click the set time button and enter 2200, then TM-/TM+ until I get a low-DV solution. Since I don't start using Rendezvous until I'm just under my target (with 5 degrees) half an orbit or so is fairly reasonable for targets and ships within abour 450km of Earth.
I've used IMFD to try and rendezvous with other targets, but the only target I got any success with was the Luna-OB1 wheel and I ended up intercepting at a 90 degree angle! Obviously I had to burn a full tank (Stock DG) to velocity match with it

 

[blane]

The lame way

I'll do it rather boring now:

IMFD "Velocity Match" will always help

 

[blane]

I tried to play a little more with tangential transfer... and I found no way to use it at all. Apparently it only works for transfers within the same reference system (inner-planetary travel).

But whenever I try to use it for a Earth->Moon or Phobos->Deimos transfer, the display switches around wildly every second. It does not matter what TEj I set, the display and numbers constantly change so it's unusuable.

Am I doing anything wrong?

 

[mbartley]

I've done well with using IMFD's off-plane target intercept mode for orbital rendezvous. However, I've found it's very inaccurate unless I go into IMFD's configuration menu and turn Nodal Regression to off.

 

[blane]

Target Intercept always worked fine for me too, but Tangential Transfer seems to be unusable.

And that's a bit annoying, because I usually want a tangential approach. So I use Target Intercept and need to adjust TEj and TIj a good deal to match my needs.

 

[jarmonik]

Target Intercept always worked fine for me too, but Tangential Transfer seems to be unusable.

And that's a bit annoying, because I usually want a tangential approach. So I use Target Intercept and need to adjust TEj and TIj a good deal to match my needs.

Tangential Transfer program was an experiment to compute a transfer orbit that oscullates with source and target orbits at the same time. Not very usefull in most cases but I have used it to calculate interplanetary launch windows.

 

[blane]

Interplanetray? Hmm, I cannot use it this way. When in LEO for instance, you cannot set REF to "Sun" unless you are out of Earth SOI. And "Mars" is an invalid target ... at least when I try it with the latest IMFD.

 

[tblaxland]

I've done well with using IMFD's off-plane target intercept mode for orbital rendezvous. However, I've found it's very inaccurate unless I go into IMFD's configuration menu and turn Nodal Regression to off.

You should have Nodal Regression off if you have non-spherical gravity sources disabled, since non-spherical gravity is the main source of nodal regression.

Interplanetray? Hmm, I cannot use it this way. When in LEO for instance, you cannot set REF to "Sun" unless you are out of Earth SOI. And "Mars" is an invalid target ... at least when I try it with the latest IMFD.

Set SRC to Earth, REF to Sun and TGT to Mars. Once you have an intercept calculated, use Orbit-Eject program to calculate the ejection burn that will put you onto the interplanetary trajectory.

 

[blane]

Ah Thanks -- I didn't realize that I have to set the SRC to Earth before I can change the reference to Sun. Got that solved -- but the initial problem remains:

The TIj and path jumps all the time whenever I enter any configuration. It does not matter if I change the TEj in any way, there just is no stable position, it constantly changes and gives various solutions (changing maybe twice a second). Hmm, I wonder if this is an effect only on my computer? I might be able to record it...

And btw: I use full realism settings and have nodal regression activated. (Just out of curiosity I changed it to "off" but this had no obvious effect on the problem)