Problem Bad redezvous with ISS

[superfofis]

I think i did something wrong somewhere, but its the second time I arrive at ISS with the stock Shuttle Atlantis to find the station slowly spinning and moving away from the redenzvous point.

I start aproximation with 0.00 relative inclination and 0.00 DTmin. But as soon i get near (2km) and start burning to slow the shuttle down, rInc and DTmin starts to swing and I find the ISS spinning and moving away.

Also, i noticed that evertytime i burn to change inclination it messes the orbit's apoapis or periapsis and vice versa.

What am I doing wrong?

I'm launching with the AscentAP and carry the Leonardo Module in the bay.

Help.

 

[Urwumpe]

Nothing big actually. First of all, the station does not have attitude control without addons providing it.

Next, I think the stock Atlantis still has the 13° angle of the OMS. so, you need to remember to pitch up 13° from the direction you plan to burn to. In SSU, the autopilot does this for you, but programming the autopilot is literally rocket science.

 

[superfofis]

Wait, so the "problem" is the OMS? If I use the translation thrusters to do the approach this problem will happen?

 

[Urwumpe]

Wait, so the "problem" is the OMS? If I use the translation thrusters to do the approach this problem will happen?

Yes, but that will create new challenges because of the longer burn time. And you should be a zero RInc....

 

[superfofis]

How about the gimbal control menu? Could some setting "fix" this 13° angle thing?

 

[Urwumpe]

No, thats for the ascent autopilot and only handles SRBs and SSMEs.

Just tested it again to be sure: Its still the 13° angle. Pitching up (or down when heads down) by 13° results in no change in vertical acceleration while burning.

 

[superfofis]

Yes, true! I forgot that. Thanks my friend

---------- Post added at 11:06 PM ---------- Previous post was at 09:48 PM ----------

man, i'll be damned. i tried to manually point to stuff with a 13º offset and found that the direction of the burn strangely aligned with a random X in the middle of the bootom part of the Orbit Hud.

I had notice this X before but never paid attention. I always tought it was some random artifact from Launch MFD or, other mod.

Turns out is exactly the direction of the OMS burn. Just point with this X and it's done.

Case solved!

 

[Tim13]

. In SSU, the autopilot does this for you, but programming the autopilot is literally rocket science.

LOL ^^^^

Good one.

Tim