Docking Operations

[Nemoricus]

I have some questions as to how docking operations should be done, as opposed to how they are done.

1. At what distance would you say docking becomes becomes a matter of actively matching relative velocities as opposed to passively waiting for your orbits to bring you close to the other vessel?

In my experience in LEO and LLO, if the two vessels are within one hundred kilometers of each other, it is quite feasible to try to maneuver directly to the other vessel. However, it's better and more fuel efficient to let your orbits bring you together. Within about ten kilometers, it's better, but you still have a noticeable gravitational acceleration changing your relative velocity, depending on how you're approaching the other vessel. Within one kilometer, it's almost solely your relative velocity that matters.

2. What would you consider to be good docking etiquette? For example, how far should you stay from the other vessel until you're actually aligned to dock and how fast should you go relative to other vessel? If the latter should vary with distance, give a formula that gives a reasonable maximum speed at very distances.

If the two vessels are similar in size in maneuverability, one should endeavor to make as little change to its attitude and velocity as possible and safe. Any vessel should attempt to keep angular velocity to a minimum except around the axis of its docking port. Both of these help with docking maneuvers.

What are your thoughts on these? What else is good docking practice?

 

[Tommy]

I would have to say not firing your engines at the other vessel is good etiquette.

 

[Donamy]

I would have to say not firing your engines at the other vessel is good etiquette.

How else are they going to know you're there ?
:rofl:

 

[ar81]

[ame="http://www.orbithangar.com/searchid.php?ID=3988"]Tutorial: Space shuttle from KSC to ISS and back[/ame]

 

[Nemoricus]

That's a very interesting and informative tutorial, but it doesn't answer the kind of questions I'm asking.

I consider myself to be competent at rendezvous and docking operations (not so much at launching and landing, but that's another story). I'm not asking how you dock, but what a good and safe docking maneuver would look like.

My first question is more geared to finding a division between the rendezvous and docking components of a mission. The numbers that I put out were based on my experience and I want to hear what others think.

My second one is meant to lay out a series of guidelines to govern how one vessel should dock with another.

I don't need any of this myself. Rendezvous and docking operations are one of those things in Orbiter that I find easy and enjoyable. I just want some opinions on how it should be done.

 

[tblaxland]

My first question is more geared to finding a division between the rendezvous and docking components of a mission. The numbers that I put out were based on my experience and I want to hear what others think.

I'd say you would have to be within 500m to be considered in "docking phase". IIRC, real life vessels approaching the ISS don't start with a "straight-in" r-bar or v-bar approach until they are within about 500'(150m). They also typically have a hold point at about 30'(10m) to check alignment before committing to docking.

 

[Nemoricus]

Hmm...another thing to consider is the fact that approaches in Orbiter aren't as precise as those space agencies plan. With practice, a skilled Orbinaut can get pretty close, but most aren't that good.

With that in mind, do you think that there would be any difference from your numbers?

Also, Orbiter has some truly massive vessels. Vespucci D stands out because it's almost a kilometer in length. An approach would be different for this vessel than for smaller vessels. There's also the unusual fact that its four main docking ports do not have a clear line to space. There's structure in the way which complicates any approach. Does anyone have any thoughts on docking with vessels like that?

 

[tblaxland]

Hmm...another thing to consider is the fact that approaches in Orbiter aren't as precise as those space agencies plan. With practice, a skilled Orbinaut can get pretty close, but most aren't that good.

With that in mind, do you think that there would be any difference from your numbers?

Using Rendezvous MFD, I can get a precision approach so close that it makes no difference. Yes, I normally fly the RL way, ie, arrive on the r-bar or v-bar at around 200m (Rendezvous MFD stops working closer than that) then move in.

I haven't flown any of the very large vessels.

EDIT: You might also be interested in [ame="http://www.orbithangar.com/searchid.php?ID=4127"]Gemini semi-optical rendezvous tutorial (v 0.3)[/ame] and the thread about it: http://www.orbiter-forum.com/showthread.php?t=9065

 

[PhantomCruiser]

...Vespucci D stands out... Does anyone have any thoughts on docking with vessels like that?

You mean docking it? Or docking with it?
I haven't flown a Vespucci in a while, but I got pretty good with it. The think to keep in mind is that she's a slug (maneuverability wise that is). The first time I docked her into the spacedock looking thing that comes with the download, it took me about 30-40 minutes or so, and that was once I was lined up. Slowly (real slow) approached and finally docked.
Docking with it... Approach from the stern using the line-up boxes as a guide, but not flying through them. As I near the back of the ship I would roll level to the docking port. Stop the rotating section to ensure a clear path. And then switch back to the DG. Once I was in between the rotating (now NOT rotating) section and the docking "collar" I would stop forward motion, and slowly translate down to the docking port, then forward again to capture.
I thought docking with a Helios was tricky... Coming in fron the side like that, not hard, just a bit disorienting.