Add a deadband for RCS and SAS

[Skybar]

What is deadband?

In the real world, gimbals could detect attitude changes to within hundredths of a degree, so the RCS would be firing constantly to correct the ship's attitude every time a very small attitude error occurred. This wastes a lot of RCS fuel. So a dead band was introduced into autopilot systems. A deadband is a attitude tolerance region in which no automatic attitude correction happens. This deadband was customizable and was adjusted as needed. So for example instead of the RCS firing every time a 0.01 degree of attitude change occurred, a deadband could be introduced within 1 degree of attitude change, so the RCS only fires if the attitude error exceeds 1 degree. This saves RCS fuel as it fires less often. The dead band can be set to varying deviations as required depending on how accurately you want your spacecraft to point in the direction you want.

How is it useful in Kerbal Space Program?

As it is useful in real life to save RCS fuel, it would help save fuel in KSP too, especially in large spacecrafts like space stations. I've built 2 large space stations and noticed that they use a large amount of RCS fuel as the RCS keeps firing very frequently to correct the space stations attitude and this causes the space station to swing and more RCS is used to try and stop it from swinging which just keeps the swinging going. It would also reduce the annoying twitching engine nozzles do on a small spacecraft as they change direction every millisecond to counter attitude errors when using the SAS. So my suggestion is to add an option in the command module control panel to toggle and set a deadband to the degree you need.

Edited November 7, 2015 by Skybar

[pandaman]

Welcome to the forums.

Good idea, seems like this should be a fairly easy thing to implement too (says a guy who doesn't know how easy it to actually do)

[Skybar]

Glad to be here.

I learned what a deadband was by reading on the Apollo Missions How Apollo Flew to the Moon (A really good book by the way) and realized that it's a really efficient thing to implement. Thought it might be really useful in KSP too given how much fine RCS control it gives, especially helpful for space stations.

[Kagame]

Welcome to the forums! *dunks Skybar in gatorade, runs away*

Good idea. I'd say a degree of deadband would be normal for everything, possibly toggleable with capslock for precision mode?

[Skybar]

Once again, glad to be here.

I agree, a common degree could be set that can be toggled on and off with a hotkey or something and if a slider is introduced in the command module control panel to adjust the deviation as you require.

[TMS]

The algorithm that holds heading under SAS was fine-tuned over several releases to address the very thing you describe.

The algorithm that holds vectors under autopilot (prograde, normal, etc) was plonked down for 1.0. It appears to use a far less sophisticated method (similar to the old ASAS algorithm that would spam RCS and shake ships to pieces) that over-corrects wildly.

I would suggest that adding a deadband would treat the a symptom, but not address the underlying cause. The way the PID-like system works needs addressing, fixing how vectors are rotated to (which is not intelligent in the slightest) and how they are held. This will improve RCS consumption as a side-effect.

[Skybar]

The algorithm that holds heading under SAS was fine-tuned over several releases to address the very thing you describe.

The algorithm that holds vectors under autopilot (prograde, normal, etc) was plonked down for 1.0. It appears to use a far less sophisticated method (similar to the old ASAS algorithm that would spam RCS and shake ships to pieces) that over-corrects wildly.

I would suggest that adding a deadband would treat the a symptom, but not address the underlying cause. The way the PID-like system works needs addressing, fixing how vectors are rotated to (which is not intelligent in the slightest) and how they are held. This will improve RCS consumption as a side-effect.

Fixing in what manner? I'm sorry, I'm not all too familiar with how the game handles vectors and holding vectors. Could you explain more about addressing the underlying cause?