Can Inline Reaction Wheel torque destroy ships?

[AstroRick]

Throwing this out there; can you have -too much- torque in reaction wheels on a ship in KSP? I've had several instances of ships going into wild gyrations during long burns with the end result of the ship shedding parts.

I've played around with fuel routing, being sure that the multiple tanks drain in succession. Current design uses 4 IRWs. Experimenting with reducing that number to see what happens.

[DMagic]

Too many reaction wheels, or any type of control surface can cause shaking, but in my experience that is mostly harmless, just annoying.

The death rattle, as I call it, is a different issue. I have no idea what causes it (parts clipping together might be an issue), but it doesn't seem to be related to how much or how little torque/control authority you have.

[sal_vager]

Yes this is definitely possible, I have a station that I made before the SAS/reaction wheel changes and it uses 24 SAS units for stability, if you remember back then if you had ASAS switched on, your stations would wobble so much they could shake apart.

Now those SAS units are reaction wheels and if they are all enabled the station starts to wobble like crazy, so I have to disable almost all of them.

[CaptainArchmage]

Even with the updated SAS, if you use more than one inline reaction wheel you can get a lot of wobble on your rocket, especially when turning. I have not had ships come apart from this on ascent, but I think it is best to be careful, unless you want to stress-test your ships.

[Murph]

Yes, it's quite possible for reaction wheel torque to pull the rocket apart. If you put loads of torque right on the top of the rocket, and there's a massive heavy-lift 1st stage at the bottom, it's quite possible for the torque to break the weakest link via bending during pitch and yaw. The fix is to avoid putting massive torque right at the top. The top stage is best to only have sufficient torque for that stage on its own, or maybe that stage and the stage immediately below it. Adding torque wheels to the top of the heavy lift lower stages, if it needs more in the early phases of flight, is far better than adding them at the top, in my experience.

[Taki117]

Totally possible, I have small satellites with a set of reaction wheels on either end. If I try to do anything with them without dampening on (by pressing caps lock) they threaten to tear themselves apart.

[AstroRick]

That does lead to another question. Is -where- you put the IRWs important. Stacking, out on outrigger tanks or the like? I'd like my large System "tug" to not fall apart...

[Taki117]

That does lead to another question. Is -where- you put the IRWs important. Stacking, out on outrigger tanks or the like? I'd like my large System "tug" to not fall apart...

The closer to the center of mass the better, also, if your ship is sufficiently large, one at each end will work wonders. Don't go too overboard and you should be ok.

[bsalis]

Now those SAS units are reaction wheels and if they are all enabled the station starts to wobble like crazy, so I have to disable almost all of them.

I think that is only because the reaction wheels are on different crafts attached by docking ports. Although the station is logically one craft, it is still seperate docked crafts in other ways. You can see this in the persist.sfs... and how docked crafts retain names when undocked etc.

The closer to the center of mass the better,

I'm pretty sure it does not matter. The (total) torque is still applied at the CoM, wherever that is.

[Murph]

I'm pretty sure it does not matter. The (total) torque is still applied at the CoM, wherever that is.

I certainly could be wrong, but I had formed the impression that the torque is applied at the location of each reaction wheel. I've certainly seen rockets doing impressions of bananas due to reaction wheels at the top and most of the mass at the bottom, or at least I thought that was what I was seeing (hard to be certain).

[Kasuha]

I think that is only because the reaction wheels are on different crafts attached by docking ports. Although the station is logically one craft, it is still seperate docked crafts in other ways. You can see this in the persist.sfs... and how docked crafts retain names when undocked etc.

I am pretty sure docked crafts make single ship. Undocked crafts retain names only if you undock them the right way, their names are retained in docking ports by which they were docked.

I'm pretty sure it does not matter. The (total) torque is still applied at the CoM, wherever that is.

I am pretty sure the torque is applied where the wheel is. I have three wheels on my orbital station and if I put them to work, they bend the whole station.

[Comrade Jenkens]

I've had space stations ripped apart by even small amounts of reaction wheels. However single launch ships can be reinforced by struts which can remove the oscillations.

[bsalis]

I am pretty sure docked crafts make single ship. Undocked crafts retain names only if you undock them the right way, their names are retained in docking ports by which they were docked.

Yes - logically a single ship. However information about the docked crafts is still stored, including the name and root part id. Take a look in your persist.sfs... here is an example from mine...

DOCKEDVESSEL
{
     vesselName = Cobra
     vesselType = 5
     rootUId = 687906975
}

I am pretty sure the torque is applied where the wheel is. I have three wheels on my orbital station and if I put them to work, they bend the whole station.

Yes - as I said. It only happens when you have multiple docked crafts. I have never seen bending on singular spawned vessel.

[Kasuha]

Yes - logically a single ship. However information about the docked crafts is still stored, including the name and root part id. Take a look in your persist.sfs... here is an example from mine...

DOCKEDVESSEL
{
     vesselName = Cobra
     vesselType = 5
     rootUId = 687906975
}

I know that part of code and it's been always inside the docking port by which you can eventually undock it. Never in the ship's original root part.

Yes - as I said. It only happens when you have multiple docked crafts. I have never seen bending on singular spawned vessel.

I had pretty hard time not to break this in half. And it was spawned as single piece, there are even not any docking ports in it. So I guess you just didn't try hard enough.

[Murph]

I retract what I said earlier, that I could be wrong. I was correct.

Here's a simple demo ship to construct which somewhat comically demonstrates that the torque force is applied at the location of the reaction wheel, and not the CoM:

Stayputnik

16x Inline Reaction Wheel (stacked)

16x Octagonal Strut (stacked)

1x Jumbo-64

1x Mainsail (if you want to go for max comedy value)

4x launch clamps attached to the Jumbo-64

Observe that the CoM is deep inside the Jumbo-64.

Use the pitch and yaw controls on the launch pad, without doing any staging, no engine, etc. Marvel at its wiggly-wobbly awesomeness!

[DrMonte]

I had a situation but with absolutely different solution.

Stacked multiple sputnicks with their own reaction wheels were breaking the whole ship. Solution was to remove the struts and allow loose wobbling. Reaction wheels were not transferring their power to the core no more.

[John FX]

Short answer, yes.

long answer, yeeeeeees, but it sort of depends.