Docking - final step (RCS): tips plz

[Brienne]

Hello,

I build a station around Mun. I dock manually. And sometimes, it's a bit tricky.
When I use RCS for last moments before docking, one side of the vessel seems to move more than the other side. Is there any tip about that?
I guess it depends on center of mass. And thruster position on the vessel.

[Buzzkil88]

yep center of mass and thruster positioning. I always have trouble with that. lol. if they are not positioned right, it might not even go the direction its supposed to go when you press a key. Goes down instead of forward. etc.

[ThatBum]

It's sort of a fundamental problem with RCS thrusters: they don't self-balance. They all exert the same amount of force regardless of where they are relative to the center of mass, so one side ends up pushing more than the other and the attitude starts drifting.

A way to mitigate the problem is to place either end of the RCS thrusters equidistant from the center of mass in designing, but this loses effectiveness as fuel is burnt. You could always just leave ASAS on, but it will probably spazz out and waste all your RCS fuel. I suppose you could put a bunch of thrusters in a row and turn them on and off as weight shifts, but that's just silly.

MechJeb 2 has an experimental RCS balancer, haven't tested it myself. You could try that if you're not one of those people who have objections about MechJeb for some reason. it's here: http://mumech.com/uploads/MechJeb2_2.0.6.zip

There was also talk from a dev interview about a balancer possibly being integrated into vanilla, but it was not definite.

Other than that there's not much that can be done. Sorry

[Brienne]

Ok, thanks. I'm not the only one^^
I continue to dock manually. Once my Mun space staion will be done, I'll make one or two kethane transfers. Then, I'll use Mechjeb (by the way, I know it can autopilot the whole flight, but didn't try yet).

[Nats]

See my other post about SAS - if you use SAS only for your docking pieces instead of ASAS it is less fiddly controlling them when docking because you dont have to constantly be turning off the ASAS and using RCS for rotation (which is right bind). Just use the RCS for translation and turn them of and use just the SAS for pitch/spin/yaw. You will find it a lot easier to dock that way. But dont use ASAS because that interferes with the benefits of SAS for dampening your rotation contol.

Put an ASAS ring onto a decoupler (perhaps grouped with your last engine) so you can get rid of it once you are approaching the station.

[Truth]

In my experience mechjeb just fails when it comes to docking, tried it for like 10 times already to dock with mechjeb but he fails really hard, hes trying to dock for like 30 minutes and just misscalculating everyting, doing it by myself every damn time... someone noticed a similar problem with mechjeb?

[ThatBum]

MechJeb 2's docking autopilot? It seems to work alright if both ships have zero relative velocity to each other.

If you mean MechJeb 1's rendezvous function built into the ascent autopilot, MechJeb needs to fly the ship at least once to get data on how it handles the flight profile. MechJeb 2's rendezvous module only works when you're already in orbit currently, but it's flippin' fantastic. It's incredibly accurate through the entire range if orbital position and altitude differences.

[Truth]

im talking about mechjeb 2.0.6, the rendezvous functions is almost perfect, but the docking module doesnt work for me. Im getting into orbit, i activate the rendezvous function, mechjeb moves my ship to the target i choose, everything fine until i activate the Docking Autopilot... Then Mechjeb just ♥♥♥♥♥ up everything, he tries to dock for like 30 minutes until hes too far away for the docking autopilot.

as i wrote, im ONLY talking about docking autopilot, rendezvous is working fine with mechjeb

EDIT // Do i have to activate the Mechjeb Docking Autopilot on BOTH ships?

[Col.Neville]

orda works alot better for docking. mechjeb par - par + helps alot as well that way you are only working in the plane between the two docking ports and not chasing your tail if you bump it and send the target spinning.

[Truth]

Yea actually some hours ago i docked for the first time using mechjeb docking autopilot, i had to activate the autopilot on BOTH planes, thats the only way the docking autopilot works for me.

[Col.Neville]

you dont have to have both running mechjeb in docking mode but it helps to have one set to prograde par - or something so the docking ship isnt having to chase it around.

[Truth]

it never worked for me with just 1 mechjeb, just doesnt work. mechjeb tried for like 1 hour to dock... but with 2 modules on docking autopilot it works fine now.

[-=Castun=- [RNGesus]]

RCS thrusters also always give maximum thrust output too from what I understand, so it's always on or off, no inbetween.

[Warsoul]

Use non shielded docking port, easier to dock. Approach really slowly. At 5m distance adjust your direction to hit target docking port (capslock on). At 2m distance; begin to spam Asas, 1 sec asas on 1 sec asas off. The docking port magnetive field gona do the job by itself. If you use shielded docking port; you prolly need to rotate your ship slowly until you find a good match to prevent opened shields collisions.

[Dukie]

I agree it is very hard to do, but if you take it slow and try to balance the RCS (I don't get it perfect aswell, but good enough to make it work) it is doable.

Also if you use Caps Lock on the final stage of the approach it makes the RCS thrust more precise (and slow) it helped me tons. Hit Caps Lock once for precision maneuvering, if you hit it again it's set to normal RCS again. I hope this helps you a bit.

This is my 10 part station. So I managed to perform 9 docks at it.

http://steamcommunity.com/sharedfiles/filedetails/?id=139425996

[bpivk]

Publicado originalmente por Duke McFishy:

This is my 10 part station. So I managed to perform 9 docks at it.

This thing must wobble like a ♥♥♥♥♥♥. :)