Space Station designs,

[FREEFALL1984]

Hey guys, I want to create my first true space station (rather than just a few fuel tanks attached together) and I was thinking of trying a new design which I'd like to run by you all. The design would consist of a habitation module to provide accommodation for at least 10 kerbals, connected to two XL girders, with a clampotron on the end. then a single "balance" module, and a single orange fuel tank attached at the opposite side, this one also has two XL girders and a clampotron. this balance tank attaches to the opposite side of the hub from the habitation module, the central hub then has two utility booms attached to the top bottom, which would each consist of two girders and with a whole crapload of batteries, and solar panels on each one, although they would be identical in order to keep balance. Then on the back of the hub I would have a fuel store consisting of 3 orange tanks with a central clampotron, and on the opposite side from the fuel store I would have a long XL girder boom with a single clampotron on the end. The idea is that when the habitation module, balance module and utility booms are attached the whole thing begins to rotate, at which point I balance the whole station by dumping fuel from the balance tank until the center of mass and indeed the center of rotation is in the exact middle of the Hub at this point the I increase the speed of the rotation until I achieve 1G for my kerbinauts. This then allows me to attach the fuel tanks and any radially symmetrical vessels while the station is still in rotation.

I have a few questions,

firstly - the game would freeze the rotation of the vessel as soon as I timewarp how can I prevent that.

Secondly - are clampotrons strong enough to achieve my goals.

Finally - would I need to match to rotational speed of the station when I dock with it, or would it allow me a little tolerance or would it simply be safer to stop the rotation?

Edited March 14, 2014 by FREEFALL1984

[Seret]

I tend to build stations fairly similar to that, about the only bit of advice I'd give would be consider moving as much mass as your practically can to the central hub. Having lots of weight hanging off the end of long struts puts a lot of force on them when they rotate. You want to put your mass as close to the point you're rotating around as possible. Connect everything using the big clamp-o-trons if possible.

You can't keep the station rotating when it's not the active vessel. Sorry! 1g would require a hell of a spin for the size you can build things at in KSP anyway.

You absolutely want the station to stop rotating when you dock. You also want to be able to rotate your docking ports to the direction your ship is approaching from. Include some reaction wheels.

Edited March 14, 2014 by Seret

[FREEFALL1984]

the only bit of advice I'd give would be consider moving as much mass as your practically can to the central hub. Having lots of weight hanging off the end of long struts puts a lot of force on them when they rotate. You want to put your mass as close to the point you're rotating around as possible.

Indeed the orange balance tank would be about 20t based on an approximate 20tons of habitation module, and serves simply to balance the system, the main fuel supply is lateral to the central hub so rotates along its own axis. As would any large interplanetary ships which dock with it

[Keymaster89]

firstly - the game would freeze the rotation of the vessel as soon as I timewarp how can I prevent that.

Yes, the game will do that and if spinning too fast i think that won't allow u to leave to KSC either.

Secondly - are clampotrons strong enough to achieve my goals.

Once copuled docking ports are strong as any other connection in your station, just place them smartly or if u made long and/or asimmetrical branches the whole station start to wobble or even broke in the weakest spots.

Finally - would I need to match to rotational speed of the station when I dock with it, or would it allow me a little tolerance or would it simply be safer to stop the rotation?

Docking is challenging already, if the docking port u're headed spin and u have to rotate around the station to keep alignement it will become a nightmare, even impossible with big ships. I strongly advice u to stop the rotation of the station while u dock. Actually i strongly advice u to don't spin the station at all if not for just play with your station a bit. Station are stationary, if u want spinning station i advice u to check some mods that have dedicated parts that do that, as i have to agree with u: spinning station are cool. Cool, but IMO not viable in stock parts.

[Seret]

Docking is challenging already, if the docking port u're headed spin and u have to rotate around the station to keep alignement it will become a nightmare

I second this. You want to lock the station down before you try docking to it. I get that you're trying to do a bit of a role playing thing with artificial gravity FREEFALL1984, but I think keeping it spinning during a docking operation is making life way harder for yourself than it needs to be. A station that's hard to dock with is a pointless station IMO.

[Nathair]

Docking is challenging already, if the docking port u're headed spin and u have to rotate around the station to keep alignement it will become a nightmare

But would you have to? If the target port is spinning around your approach axis,

, then wouldn't the situation be exactly the same as for a stationary port? (Until you dock, obviously.)

Hmm... must go try this.

[Keymaster89]

But would you have to? If the target port is spinning around your approach axis,

, then wouldn't the situation be exactly the same as for a stationary port? (Until you dock, obviously.)

Well i meant spin around the station, as it translate with the spin of the station... if the port spin while being on the axis it won't make any difference, u just have to equilize the spin when u are at 4-5m afar.

[Seret]

If the target port is spinning around your approach axis

Sure, you could probably make that work if you started with the station stationary, pointed its docking port at the approaching ship, then spun it up and matched the docking ship to that spin. Bit of a faff, and I'm not sure the roleplayers would find it very satisfying.

[TechnicalK3rbal]

I would suggest installing infernal robotics, they have (hinges? I can tremeber what they call the little spinny things) that you could use for this, and you could just start the rotation instantly again after timewarping.

[*Aqua*]

(hinges? I can tremeber what they call the little spinny things)

Thy called them docking washers

[FREEFALL1984]

I would suggest installing infernal robotics, they have (hinges? I can tremeber what they call the little spinny things) that you could use for this, and you could just start the rotation instantly again after timewarping.

Looked at the infernal robotics site spaceport page and it says they're not yet compatible with career mode so I can't use them

Edit: silly me I didn't read the small print

Edited March 14, 2014 by FREEFALL1984

[*Aqua*]

Infernal robotics is compatible with the career mode.

The text on space says:

Updated for 0.23 with Techtree!

[FREEFALL1984]

1g would require a hell of a spin for the size you can build things at in KSP anyway.

Not really, in fact I imagine it would be something like a pleasant 15RPMish but I could be wrong, remember the full structure would end up being about 12 XL girders long, I imagine these are around 3 meters long so that about 36 meters in length, including tanks and habitat modules, My concern is whether the structural elements would be able to cope, a pair of 20000kg weights rotating fast enough to produce 1g would apply a total of 392kn of force to the central hub. excluding the forces required to rotate the weight of the docked vessel and fuel supplies. Not the sort of force to be simply sniffed at lol

In total the station would be around 36 meters wide by 12 meters tall unloaded, but with a stack of fuel and a docked ship it would probably be about 36 meters deep depending on the ship. I could be wrong with the dimensions but Its a best guess based on the rocket diameters

[Jouni]

That 15 rpm is quite a lot, assuming that kerbal physiology is similar humans. According to Wikipedia, 2 rpm is a generally accepted upper bound for what most people can handle for extended periods of time. To get 1g with that, you need the radius of rotation to be over 200 m. Some people can apparently handle up to 7 rpm, which could provide 1g with a radius of 18-19 m.

[Pecan]

a pleasant 15RPMish

Have you considered the size of fuel-tanks and engines you'll need to spin this ~200t station up to 1 revolution every 4 seconds? Then stop it again every time a ship wants to dock. The most effective place to put those engines would be radially towards the ends of the habitation and counterweight modules - pointing sideways, of course. That means an awful lot of torque on the docking ports though. More practically you'd want to place them further inboard, which will necessarily be less effective. It will probably be very difficult to balance their thrust to make sure you're not introducing unwanted translation as well as rotation. I'm sure this is possible but it certainly won't be easy.

[Seret]

Not really, in fact I imagine it would be something like a pleasant 15RPMish but I could be wrong

It's about 7rpm. Try it though, that's pretty fast for a large structure. You're talking about 13ms^-1 of tangential velocity on the far ends, that's 48kmh^-1.

[FREEFALL1984]

Have you considered the size of fuel-tanks and engines you'll need to spin this ~200t station up to 1 revolution every 4 seconds? Then stop it again every time a ship wants to dock

The idea would be that it would never need to stop, and that the docking port would remain stationary and rotate on its axis,

That 15 rpm is quite a lot, assuming that kerbal physiology is similar humans. According to Wikipedia, 2 rpm is a generally accepted upper bound for what most people can handle for extended periods of time. To get 1g with that, you need the radius of rotation to be over 200 m. Some people can apparently handle up to 7 rpm, which could provide 1g with a radius of 18-19 m.

I believe the Coriolis effect would be negligible due to the linear design of the station, making all points be as close to the center of rotation as possible meaning no cross forces and no dizziness for the kerbals, although we do have to remember that these guys can happily survive reentry while strapped onto the nosecone of a rocket travelling at MK10 through the soupy bit of atmosphere. So I think a little dizzyness and nausea is the least of their problems

[Seret]

The idea would be that it would never need to stop, and that the docking port would remain stationary and rotate on its axis,

It would stop spinning every time the station went "on rails" (ie: you switched to another ship not in the vicinity of the station). So you would need to spin it up every time you rendezvoused for docking. That's a limitation of the game unfortunately.

[Kerba Fett]

I've never tried it, but this mod is supposed to allow things to continue rotating in timewarp. http://forum.kerbalspaceprogram.com/threads/67821-Timewarp-Rotation-Fix

I played with rotating stations quite a while ago, but haven't built one in a while. If you want to dock at the hub, it's pretty straightforward. Just add some roll and fly from the chase view or IVA. The background might make you a little dizzy, but if you just focus on the station it's just like normal docking. Another option if you were using the infernal robotics mod would be to put an unpowered rotator and split your station into a stationary docking hub and a rotating habitat module.

I don't think you're going to need to use fuel to balance the station. Just build symmetical. If you did try to spin it up with something attached off balance the station would probably tear itself apart before you got the fuel transfered to balance it. So you'd need another mod to show your center of mass before you tried to spin it.

If you haven't already seen it, Wayland Industries has a station ring for .18. You'd need to update the config file to use it in the career of .23, but you could copy most of what you need from the config file of the hitchhiker container.

There's also this mod that has a ring with IVA. http://forum.kerbalspaceprogram.com/threads/64442-0-23-Habitat-Pack-v0-3-Flat-hab%21

As for the people suggesting that you need to turn your station to face an approaching ship, that's just silly. If you can fly well enough to dock, you can fly well enough to get to the other side of a station and dock there.

[Seret]

As for the people suggesting that you need to turn your station to face an approaching ship, that's just silly. If you can fly well enough to dock, you can fly well enough to get to the other side of a station and dock there.

Sure, it's a lot quicker and simpler to just turn the station though. Why make life any harder for yourself than it needs to be? I always turn my docking target to face the approaching ship.

[Jouni]

I actually find it harder and more annoying to switch ships and turn them to face each other, instead of just docking. Switching ships is essentially a context switch, so you lose track of what you are doing, and have to reorient. Of course, I dock ships much more often than launch rockets from Kerbin, so docking has become a routine task.

[Seret]

I do it once I've zeroed out all relative velocity, before the approaching ship starts its approach (or maybe after if I'm feeling frisky). Quick switch, set "control from here" on a port, go to map and target the approaching ship, then rotate onto the pink on the navball. Easy peasy.

Obviously not advisable if you're a launch-straight-to-rendezvous kind of player

[Kerba Fett]

I do it once I've zeroed out all relative velocity, before the approaching ship starts its approach (or maybe after if I'm feeling frisky). Quick switch, set "control from here" on a port, go to map and target the approaching ship, then rotate onto the pink on the navball. Easy peasy.

Obviously not advisable if you're a launch-straight-to-rendezvous kind of player

This is exactly what I meant on my post. You're doing the same thing as I do to dock on the backside of a station except that you switch ships twice and think that makes things easier.

If you can kill all relative velocity before you get to the station then why can't you wait till after you drift past and do it?

And if you can rotate a station to center a target in the navball then why can't you rotate the ship you started in to face the station?

And once you've killed all relative velocity and turned either ship you're still going to have to approach, line up with the docking port and connect.

Your way seems like a LOT more work. You not only have to push the key to switch vessels twice, you also have to target the station twice.

[Seret]

If you can kill all relative velocity before you get to the station then why can't you wait till after you drift past and do it?

You could, it just takes longer. No guarantee that you're drifting past on the right vector to be anywhere near a good approach for aen empty docking port either.

And if you can rotate a station to center a target in the navball then why can't you rotate the ship you started in to face the station?

You'll have to anyway. Rotating the station just saves translating onto the line of the port you're aiming for, and then aligning.

And once you've killed all relative velocity and turned either ship you're still going to have to approach, line up with the docking port and connect.

Yup, or to put it more succinctly: dock. You can't really dock without docking!

Your way seems like a LOT more work. You not only have to push the key to switch vessels twice, you also have to target the station twice.

You have to re-target the station anyway, when you target a docking port for the final approach instead of the station as a whole that you had targeted for rendezvous. Aligning the station to the approaching ship honestly takes me about 5s on a small refuelling station (switch > target > rotate > switch), maybe longer on a big one if it's slow to rotate. I find my way much faster, and it breaks the operation down into steps where I'm only doing one thing at a time, which suits my simple one-track brain.

I'm assuming you know about using [ and ] to quickly switch ships? I could see how you'd find switching tedious if you were doing it through the map or the tracking station.

[Jouni]

For me, the tedious part is waiting for the target to turn. For big ships and stations, turning around and stabilizing can easily take a minute or two. If the target is easily maneuverable, turning it around is in a sense even more annoying. (I mean, if there is nothing challenging in turning the ship, why I have to wait for many seconds, instead of it just turning instantly to face the correct direction. It feels like a pointless cutscene I can't skip.) Flying a ship around obstacles, on the other hand, is fun and relaxing.