Large ships and S.A.S

[Chocki]

We all know large vehicles handly like an cast iron tub filles with lead.

I assume this is because of a low sas torque to weight ratio, culminating in a slow non rcs rotational rate.

My question is, will adding more sas units, and thus more torque help the rotation (is the proper term transition) rate?

I am trying to get a large long ship (puller attached to a probe dock, attached to a lander with rover) to handle better, so I don't have to burn and carry so much rcs fuel.

[capi3101]

Shouldn't; if anything, adding more SAS to a large ship will make it less likely to turn (SAS's function is to counter unwanted rotation). To make a tub more maneuverable in space, you've got to go with more RCS.

[Vanamonde]

SAS doesn't resist turning when it's turned off, so it doesn't make steering harder. However, it doesn't help turning in on mode, either. It simply resists turning while turned on, and that's all. But the thing is, most of the time you don't need to turn rapidly anyway. For big ships, I just let them take 5-10 minutes to rotate. What's the hurry?

[capi3101]

SAS doesn't resist turning when it's turned off, so it doesn't make steering harder.

Eh...it adds mass. In makes steering harder in that sense.

[RoboRay]

Adding SAS modules does not make your ship easier to turn, as SAS torque does not respond to your control inputs. (It tends to actually make it harder to turn, due to the added mass). All SAS torque does is resist rotation.

[Chocki]

Good thing I asked. I figured sas helped with the non powered rotation.

So, the only solution to help a large ship change headings faster is rcs.

My hurry is mainly for docking concerns where sas lock "t" can't hold a heading. The large beast just slowly moves away, making facing the docking ports a constant battle. I can leave rcs on, but then it eats fuel with a small wobble back and forth.

I guess I just have to get better at designing balanced ships, and docking faster.

[Aladran]

If you want to improve large ships handeling, the easiest way is with RCS thrusters.

You don't need a lot of them, just 4 at the tip and 4 at the tail of your ship and voilà, you can easily maneuver.

Just don't forget to turn RCS off once you're done with it, else the ASAS will end up draining all your mono propellent.

[RoboRay]

Good thing I asked. I figured sas helped with the non powered rotation.

So, the only solution to help a large ship change headings faster is rcs.

My hurry is mainly for docking concerns where sas lock "t" can't hold a heading. The large beast just slowly moves away, making facing the docking ports a constant battle. I can leave rcs on, but then it eats fuel with a small wobble back and forth.

I guess I just have to get better at designing balanced ships, and docking faster.

Your problem of staying aligned with the docking target doesn't have anything to do with the ability of SAS or ASAS to hold your heading.

Think about this:

Your craft are in orbit, not rotating, but following a curved orbital path around the planet. Your two ships are parked nose to nose, 50m apart. A quarter of an orbit later, the one out front is now pointed straight down at the planet, while the one in back is pointed straight up at the stars. Half an orbit from the starting point, the craft are now tail to tail, still 50m apart, simply because of the curved path they follow, and they are not rotating to match the curvature.

This apparent rotation can be eliminated by turning both craft so that they point along the Normal axis, which is 90 degrees off your prograde direction, and on the horizon line of your NavBall. So, if you're orbiting to the east (heading 090), turn your craft to face north and south. This causes the craft to "roll" as they orbit rather than "pitch", giving you a stationary target to dock with.

[Vanamonde]

Eh...it adds mass. In makes steering harder in that sense.

The OP is specifically asking about large ships, and SAS modules weigh in 0.07 mass units per. You could pile a bunch of the things on there before you noticed a significant reduction in rotation rate.

[RoboRay]

The point is that SAS modules never improve turning rate; they only harm it (even if it's just by a tiny amount).

[Chocki]

I decided too scrap that design, and make a smaller, more efficient design. The fact that the main engines thrust bloom happen to hit the rovers angled solar panels sending it into a spin, forced a redesign.

I also found myself holding down rcs (like you would a fps), stopping that habit fixed my rcs fuel issues.

I am now at the mun, mapping for a good landing spot. It will be quite a learning experience.

[Smorfty]

sas doesn't provide any torque

it's the command module, currently in use that does