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SAS Abruptly Changes Craft Heading When Switching From Surface Velocity to Orbital Velocity


Davidian1024

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Reported Version: v0.1.5 (latest) | Mods: none | Can replicate without mods? Yes 
OS: Linux Ubuntu 20.04.6 | CPU: AMD Ryzen 5 3400G | GPU: NVIDIA GeForce GTX 1080 Ti | RAM16GB

 

Background

This is something that frustrated me greatly in KSP1, especially when I was new.  It has been brought over to KSP2, and I find myself having to continue to work around it.  I reported this in the past but it was archived.

I want to try to make a better argument this time.

Description

SAS automatically switches from surface velocity to orbit velocity when you ascend above a certain altitude.  Over Kerbin this altitude is ~36000m above sea level.  This number is different when you are above other celestial bodies.  It generally seems to be about halfway between sea level and the top of the atmosphere.

The biggest problem with this is that SAS will suddenly start aiming the craft in a potentially completely different direction without any warning.  If this happens in the middle of a burn, it can have disastrous effects.

The reason SAS switches directions is because surface velocity and orbit velocity have completely different target sets.  And they each map to a target in the other set.

Surface Prograde/Retrogradde <-> Orbital Prograde/Retrogradde (These are usually very close, but can be significantly different.)

Surface Up/Down <-> Orbital Radial Out/In (These can be as much as 90 degrees different.  Flying straight up.)

Surface North/South <-> Orbital Normal/Anti-Normal (Can be as much as 90 degrees different.  Polar orbits.)

The core issue is that SAS will suddenly start aiming the craft in a potentially completely different direction without any warning.  If this happens in the middle of a burn, it can have disastrous effects.

Videos:

Spoiler

 


 

System Specs

Spoiler

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Edited by The Space Peacock
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