How to balance command seats?

[Vector]

I have tried placing the command seat in the 'perfect' center, but when a Kerbal is sitting in the seat, it is still off balance and wants to tip when thrust is applied.

Any tips and tricks for getting it to fly straight when a Kerbal is in the seat?

Edited November 14, 2013 by Vector

[Geschosskopf]

EVA Kerbals weigh a fair amount and that weight is applied when they sit in lawn chairs. As you can't add Kerbals in the editor where you can see the CoM thing, you just have to trial-and-error it.

One way to do this is to get Infernal Robotics (and you might also need TT's Multiwheels). What you're looking for is a free-swinging pivot. Built your rocket, put the pivots at the CoM, and attach launch clamps to them. Then build a structure of the side with a capsule so you can EVA the Kerbal out of it and walk him to the lawn chair. Once he's in the chair, see how the rocket pivots and adjust the seat position accordingly.

[700NitroXpress]

Use an SAS module for stability or put the smallest octagonal probe core on the top and then add the chair to that, smallest core is 0.6 mass.

Or use a combination of both, shown here.

This craft flies well with the kerbal on top of it, it has a small probe core as the main pod and an advanced SAS module for better stability.

Edited November 11, 2013 by 700NitroXpress

[mangekyou-sama]

^ Worse fate than an electric chair

[700NitroXpress]

^ Worse fate than an electric chair

Gotta love those G forces!

[700NitroXpress]

Or you can use a design without SAS modules, but still get the SAS advantages with the super lightweight probe core.

Shown here is my SSTO Rocket Chair:

[Deadweasel]

What if someone were to work out how much those EVA'd kerbals weigh, THEN create a dupe version of the control chair, but with mass increased AS IF THERE WERE A KERBAL IN IT?

That way you could get the CoM indicator to work for a seated pilot, and once it's all balanced out, swap it for the regular one before launch.

EDIT: Quickest way I can think of is a chair on a pod, check the (i) tab in Map view. EVA the pilot to sit in the pod, check the (i) in Map view again.

[sidew]

Gotta love those G forces!

Stapp Kerman is testing...

[jwilhite]

What if someone were to work out how much those EVA'd kerbals weigh

The figure I saw somewhere in these forums is 0.15 per Kerbal. Sorry I don't remember where I saw it.

[Deadweasel]

The figure I saw somewhere in these forums is 0.15 per Kerbal. Sorry I don't remember where I saw it.

Actually....

http://forum.kerbalspaceprogram.com/threads/31532-how-much-does-a-kerbal-weigh

Answer: .09t

EDIT:

And now that that is settled, I'm off to do just what I suggested, because I too have ships that require specific balance if somebody is crazy enough to sit in the chair.

Edited November 12, 2013 by Deadweasel

[Vector]

I like this solution.

One problem with adding counterweights is that the command seat also has an unusual drag coefficient, so even if the mass is balanced, it still won't fly straight in an atmosphere.

One question that remains is when a Kerbal is sitting in the chair, does the Kerbal have drag coefficient of 0.2, or the same as the chair? If the Kerbal in the chair has a different drag coefficient from the chair, then in an atmosphere the center of drag will never match the center of mass, and you will always have some moment.

[Deadweasel]

Awwww nuts!

So now we need to know the drag coefficient of a riding kerbal, which is the KSP equivalent to asking the airspeed velocity of an unladen swallow...

(hint: don't say 'I don't know'! Stall for time; I'll go work it out...)

[whistlehead]

What nobody's suggested yet is...

Strap TWO Kerbals to your rocket!

[Deadweasel]

Would be nice, but it's not always feasible to do. For example:

The dropship has a top seat for the second rover driver (the other is piloting the dropship). The top seat is balanced on the ship, so everything behaves normally in hover mode. Lateral flight? Ehh not quite so much. XD

[Tokay Gris]

I do have another problem that arises when you place the command seat like that and it has nothing to do with balance.

If the command seat is placed like yours, the vessels "forward" is right. ....

So, if you use Mechjeb or similar, it will try to "righten" the vessel. And it will turn to the left.

If you launch something like this, pay attention to the horizon on the Navball. If you SEE the horizon, it probably is the solution....

I did not count how many vessels of mine were thundering parallel to the ground and slamming into something until I noticed that.

[Deadweasel]

I do have another problem that arises when you place the command seat like that and it has nothing to do with balance.

If the command seat is placed like yours, the vessels "forward" is right. ....

So, if you use Mechjeb or similar, it will try to "righten" the vessel. And it will turn to the left.

If you launch something like this, pay attention to the horizon on the Navball. If you SEE the horizon, it probably is the solution....

I did not count how many vessels of mine were thundering parallel to the ground and slamming into something until I noticed that.

Huh? Wait a tic... Are you saying that the seat's orientation is off by 90 degrees to the right from its appearance? I don't usually use the seat as a control point (since there's no weight difference with a pilot in the cockpit anyway), but I'm pretty sure I've flown that ship from that seat a time or two, and never noticed the navball differing from the capsule's orientation..

[Tokay Gris]

Huh? Wait a tic... Are you saying that the seat's orientation is off by 90 degrees to the right from its appearance? I don't usually use the seat as a control point (since there's no weight difference with a pilot in the cockpit anyway), but I'm pretty sure I've flown that ship from that seat a time or two, and never noticed the navball differing from the capsule's orientation..

Well.... the orientation is the direction a Kerbal sitting in it looks at.

IF the only possible control point is the seat itself, then yes. It points the direction the Kerbal looks at.

But if you have different control points, like a small octobrain beneath the seat, you need to pay attention which one actually controls.

Like this one:

At launch, the controlling point is the small capsule to the left. So you need to change that so that the rocket gets of the ground.

Once landed, you change the point again to the capsule. Makes roving easier.

So: But once you want to get of Eve and the Kerbal jumps into the seat on top, you have to change the control point to the small octobrain underneath the seat. Otherwise it will be in the direction the seat points.

I don't know if this poses any problems if you are not using an autopilot (like Mechjeb), but it certainly messes up Mechjeb....

[Tank Buddy]

You can use 2x symmetry, put the seat near the middle and when the two overlap, you don't move the mouse and press shift-x to decrease the symmetry to 1x.

[Andrew Hansen]

It looks like nobody has yet suggested Editor Extensions! It has this awesome thing called Vertical Snap, which will allow you put a command seat right snap in the middle of a fuel tank.

As for placing a chair vertically like you showed in the original post... that trick doesn't work because the chair has no vertical attachment nodes as far as I know. But I think that Tank Buddy above me suggested a really great idea.

You can use 2x symmetry, put the seat near the middle and when the two overlap, you don't move the mouse and press shift-x to decrease the symmetry to 1x.

Additionally, using Editor Extensions, you might try switching between VAB and SPH modes. They offer some different ways of attaching things, and often radially attaching something in VAB mode will work different in SPH mode.

[Vanamonde]

You can use 2x symmetry, put the seat near the middle and when the two overlap, you don't move the mouse and press shift-x to decrease the symmetry to 1x.

This is how I place goo pods, but I think the issue with seats is that the COM changes when a Kerbal is put into the seat.

[Deadweasel]

Well.... the orientation is the direction a Kerbal sitting in it looks at.

IF the only possible control point is the seat itself, then yes. It points the direction the Kerbal looks at.

But if you have different control points, like a small octobrain beneath the seat, you need to pay attention which one actually controls.

-snip-

At launch, the controlling point is the small capsule to the left. So you need to change that so that the rocket gets of the ground.

Once landed, you change the point again to the capsule. Makes roving easier.

So: But once you want to get of Eve and the Kerbal jumps into the seat on top, you have to change the control point to the small octobrain underneath the seat. Otherwise it will be in the direction the seat points.

I don't know if this poses any problems if you are not using an autopilot (like Mechjeb), but it certainly messes up Mechjeb....

Oh, well that's an issue with a stock command part getting default control, not a problem with the seat's orientation itself.

In my case, if there's no pilot in the capsule, but a kerbal in the topseat when the ship gets focus, the orientation is on the chair. There are no probe bodies to muck up the control method unexpectedly. If it ain't manned, it ain't flying.

The game seems to have an order of priority where control focus is concerned. Top priority is a manned module/capsule, THEN a probe body, THEN a manned chair. If there's a capsule and chair but no probe body, the empty capsule will get command authority every time. I suspect that might have something to do with why a command chair isn't considered eligible as a root part.

[Sirine]

Well, trial and error.

My Eve lifter did facing the same issues as the OP suggested.

My solutionl, I just repeatedly move the command chair (At VAB), so, when a Kerbalnaunt seat on it. It still going up straight.

[Jarin]

The example pictures on the first page don't have ladders... how do you get the kerbals in the seat? o.o