Space Station Docking Arrangement Tips

[Kyrt Malthorn]

Hello all. I'm hoping to get some ideas for space station designs. I'm realatively new to the game, but I've figured out a lot so far. (Okay, I used lots of tutorials and the wiki to give me a boost.)

One of the ongoing missions I'm currently running in my career mode game is an orbital space station, which I'm using as a "gas station" as well as a staging area: I have a few ships that I simply want to live in orbit, and docked at the space station seems a natural place to keep them, and re-fuel them. Naturally I need to deliver fuel to my station with tankers from the surface too.

My problem looks like this...

Outlined things so others can make sense of it.

Green= My station at present.

Blues= Ships presently docked at my station.

Yellow= Incoming tanker.

Red dots= Docking ports in use.

In my standard docking proceedures, once I kill relative velocity and matched my orbit to my station, as I'm approaching slowly from a few hundred meters, I switch to control my station, turn on lights and such for convenience, select "control from here" on the docking port I want to use, and turn the entire station so that the crosshair is in line with the target indicator. My intended port is now facing my incoming tanker's. Makes life a lot easier if I can control the station's orientation so my tanker doesn't have to work harder, and it can deliver more fuel.

Problem: my station has become an absolutely uncontrollable BEAR to turn with ships semi-permanently docked to it. I HAVE to use RCS because my reaction wheels (ASAS, the one with 15 torque.) aren't cutting it. I had to shut off the docked ships' reaction wheels because they were fighting each other so badly the station would never stop wobbling and threatening to tear my ships off their docks.

(And of course, my station is incredibly inefficient with mono now because I hadn't bothered to line up the RCS directions at.)

My major concern is the docking port as a structural weak point and the wobbling/bouncing kinda killing any attempts at re-orientation.

I know I'm wordy. All this to ask: does anyone have any inventive station designs that somehow balanced docked ships with center mass/means of control, so that they aren't jerked around a lot?

Some ideas I already had but not sure are feasible:

- Multi port docking. (Or Clamp-o-tron Sr. - I haven't unlocked that yet.) Pros: greater docked stability. Cons: this would add deadweight to my ships - why carry extra ports just for the time it's going to be mothballed?

- Inline docking. Everything that's there to stay has a docking port at either end and they dock in a gigantic pole so at least one axis (roll) remains easy, my ports for tankers can be mounted radially so that's all the rotation I'd really need, let the tanker take care of the rest. Pros: simple. Cons: if I want a ship out of the middle of a pole I have to reconnect the ends, and a pole of ships is unwieldy.

- Don't leave things docked. Pros: solves the maneuverability and structural issues completely. Cons: Lot harder to manage and remember who got a fill-up and who still needs it when I launch my next tanker.

Does anyone have designs that offer more stable solutions?

Edited August 4, 2015 by Kyrt Malthorn

[Sharpy]

The basic approach is: It's called Station, not Motion for a reason. Don't move it. Turn that goddamned tanker around and align it with the station, not vice versa.

If you don't want to maneuver all around with a giant, just put a bunch of docking ports facing in various directions all around the station so that you can align it with any of them.

Edited August 3, 2015 by Sharpy

[capi3101]

I would tend to agree with Sharpy - you want to leave your station's orientation as is; the tanker is the piece that should be moving.

If you're not adverse to them, two mods I would recommend are RCS Build Aid and Docking Port Alignment Indicator. The first helps you construct your designs to minimize the amount of adverse torque you produce from RCS thrust (and as a bonus is incredibly helpful when it comes to spaceplane construction), the second helps with aligning your docking ports - use it correctly and you don't need any other instrumentation to dock; docking almost becomes a trivial process. I would highly recommend grabbing both mods, especially if (like me) you plan on using space stations as waypoints/fuel depots a lot.

[Snark]

The basic approach is: It's called Station, not Motion for a reason. Don't move it. Turn that goddamned tanker around and align it with the station, not vice versa.

If you don't want to maneuver all around with a giant, just put a bunch of docking ports facing in various directions all around the station so that you can align it with any of them.

^^This.

One thing that helps quite a bit is to make the station's docking ports stick out as far as possible from the main body. I typically start with something like this:

Plenty of opportunity to approach it from any direction. Later on, as I accumulate more ships and need more places to add on docking ports, I can just add on "expansion nodes" that add more sticky-outy ports, like this:

[AlanP]

Here is a different and somewhat difficult suggestion. Plan your arrival when the docking port you plan to use is facing the direction your are arriving from. Don't ask me how to do this I'm only the idea man.

[eonmoon]

another nice thung is if your far enough in the tech tree mechjeb can dock for you, another idea is set your primary docking ports to a north south axis

[match]

Just like Snark's layout, but I use structural fuselage instead of the girders. They are lighter and I light them with different colors which allows a decent visual from 200 m.

From there, I adjust approach to drift to the correct side.

[Kerbart]

The basic approach is: It's called Station, not Motion for a reason. Don't move it. Turn that goddamned tanker around and align it with the station, not vice versa.

If you don't want to maneuver all around with a giant, just put a bunch of docking ports facing in various directions all around the station so that you can align it with any of them.

While I fully agree with you it did surprise me that it seems standard procedure for ISS to rotate the whole thing around for docking purposes. Of course they get to bold the parts together through a rigid frame, as opposed to depending only on wobbly docking ports to put all the parts together.

[ajburges]

Possibilities:

Align the ports for massive craft along the normal Axis. This allows you an approach that is clear of obstruction and you can use ascending/descending nodes to plot arrival (you want intercept between the two at near 0 inclination)

Once you rendezvous, don't dock. instead use RCS to establish a circular orbit of matching period to your station. Since you have the same period, your craft will proceed to dance around each other without much change is distance. Since the don't rotate in orbit, your desired port will face you within an orbit!

Create an RCS tug (or pair) to properly manhandle you tanker into position.

[StormKat]

Kyrt, Look through the Space Station showcase thread. You will find several designs that will work for you.

http://forum.kerbalspaceprogram.com/threads/22251-Showcase-SPACE-STATIONS!-Post-your-pictures-here

[Kyrt Malthorn]

Thanks for all the responses and thoughts, constructive and snarky alike. Lot of things to think about in future station construction.

While the "Dont Move the Station" argument has merit, especially with larger stations I would think, in defense of rolling the station it IS more efficient if the station can turn with greater RCS efficiency (or better yet, reaction wheels) than a big fat tanker can maneuver around it and turn around and get moving towards it again. As a relative beginner I would have a harder time pulling that off, I think.

Oh, and maybe the station SHOULD be called Motion because it's screaming along at 2280 m/s (5100.21 mph) above the planet's surface. We really ought to purge the notion of things in space being stationary. That's Surface Dweller Thinking and contemporary sci fi.

[Nich]

For rotating stations best bet is to turn off SAS. Hold until you start to move then just let it rotate. GO VERY SLOWLY wobble will diminish on the 2-3 minutes it takes to reorient. I normally only use one 1.25m reaction wheel for stations up to 100t

[Warzouz]

Tips

- Separate you power gen (especially solar arrays) from the docking area. You don't want to damage them.

- Built yous station that you can easily understand them. I usually always do the same global design.

- It's easier to integrate a tank into the main part of the station. the docking rings are for lander refuel and return ships.

- Refueller containers dock as small ships, unload fuel to the main tank and you can ditch them.

- A extension dock at the bottom to add parts (to upgrade or patch a the station).

Few clickable picture

A hyperedit test of my Duna station into Eve atmo (to test future mission there)

Eeloo mission : A 200T payload to LKO launch for the Dres space station, and the space station in cruse configuration arriving at Eeloo. Finally the The refueller section landing at Eeloo

Jool mission : same space station, the internal tank is a double size. The two last pictures shows the station is regular configuration. It can be moved as I can balance th fuel to avoid thrust offset. I visited Pol, I'm now in Bop SOI and plan to go th Vall.

A separate mission at next window will bring along a plane for Laythe and a dedicated lander for Tylo.

Edited August 3, 2015 by Warzouz

[Skorpychan]

^^This.

One thing that helps quite a bit is to make the station's docking ports stick out as far as possible from the main body. I typically start with something like this:

http://i.imgur.com/YOe0uBe.jpg

Plenty of opportunity to approach it from any direction. Later on, as I accumulate more ships and need more places to add on docking ports, I can just add on "expansion nodes" that add more sticky-outy ports, like this:

http://i.imgur.com/ikQ8Yrn.jpg

For getting it out of LKO efficiently, you can use separate craft as extenders. Have close-in ports covered with fairings, but then have little craft that are basically a long section with docking ports each end, that can be send up efficiently.

KSP really has a need for extendable arms.

[Norcalplanner]

Sounds like you need more reaction wheels near the middle of the station so that you can still turn it with reasonable effort while ships are docked. I highly recommend KJR if you don't have it installed, since it also strengthens docking port connections. In terms of design, I've found that as long as I have a 2.5m docking port on the end opposite the engines, I can generally build my way out of any problem.

[Snark]

Sounds like you need more reaction wheels near the middle of the station so that you can still turn it with reasonable effort while ships are docked.

Reaction wheels have the same amount of torque for rotating the ship no matter where they're placed-- it doesn't matter where they are, putting them at the center of the station won't make it any faster to turn.

That said, if the station is big and floppy, it could be useful to have the reaction wheels distributed around the station rather than all in one spot, to reduce wobbling (i.e. so that they all try to rotate together, rather than just applying a huge torque in one spot).

If you do decide to rotate the station using RCS, turn on fine-control mode to reduce wobble and shake. Here's a detailed explanation, but the TL;DR is that this turns on a really cool and often overlooked game feature: it does math and proportionally throttles the individual RCS ports to give smooth operation.

[Kyrt Malthorn]

If you do decide to rotate the station using RCS, turn on fine-control mode to reduce wobble and shake. Here's a detailed explanation, but the TL;DR is that this turns on a really cool and often overlooked game feature: it does math and proportionally throttles the individual RCS ports to give smooth operation.

Now THAT is one of those super useful tidbits that makes joining this forum worth it.

[Geher]

While I fully agree with you it did surprise me that it seems standard procedure for ISS to rotate the whole thing around for docking purposes. Of course they get to bold the parts together through a rigid frame, as opposed to depending only on wobbly docking ports to put all the parts together.

Do they also rotate the ISS when a ship arrives? I only know that they sometimes do it, when undocking a craft, so that it is facing retrograde or prograde. The undocking mechanism includes an elastic spring which pushes the craft away. When the craft is facing prograde it will end up in a slightly higher orbit, when facing retrograde in a slightly lower orbit. They wait until they're far enough away from the ISS until they use the thrusters of the craft again. This way they ensure that the ISS doesn't get "dirty" by rocket exhaust. ESA made a nice video about that:

. At 4:15 they explain why they sometimes rotate the ISS.