Jump to content

youtubers don't use SAS?


Recommended Posts

Probably because the craft(s) in question is designed to fly well with SAS off. 

I'm not a spaceplane guy,  but I'm under the impression that,  in most cases, a well designed spaceplane will fly better with SAS off while in atmosphere. 

 

Link to comment
Share on other sites

Depends on skill level for building a plane.  Well balanced planes handle better if you simply trim them instead of using SAS because it turns more fluidly during banking and the like.  Your SAS doesn't fight your plane's natural tendency to turn when it's off.  It does however require knowing the plane pretty well to know what to trim it to.

Link to comment
Share on other sites

Was about to include in my post "hopefully someone with better understanding will show up soon to say if my idea is correct"  . 

I didn't, just posted instead.  And wanderingkid posted 1s later. 

 

 

Link to comment
Share on other sites

They're probably using a joystick with trim controls and/or flying well-balanced planes. Flying planes on a keyboard without SAS is pretty tough to be sure.

Link to comment
Share on other sites

2 hours ago, Spricigo said:

Probably because the craft(s) in question is designed to fly well with SAS off. 

I'm not a spaceplane guy,  but I'm under the impression that,  in most cases, a well designed spaceplane will fly better with SAS off while in atmosphere. 

 

Youtubers (*staple vegetable high in antioxidants)

SAS in the default "stability assist" setting makes things very jerky, especially if you are flying on keyboard.

It remembers the nose attitude you had the last time you touched the controls,and tries to maintain that.   Every time you apply an input, this resets.  SAS might be holding the nose up at a 10 degree AoA,  but if you touch the rudder to remove a 5 degree sideslip this resets everything and the nose falls to 0 degrees AoA,  the plane stops generating lift and goes into freefall.

Problems with SAS -

  • pitch - SAS tries to maintain the same nose attitude with respect to Kerbol, the sun, rather than the planet you are flying around.  This means the nose slowly rises as you go around the planet , the aircraft will eventually stall if you don't correct this.
  • Heading - Again, absolute heading is what it tries to maintain.  If you are north of the equator this will change as the north pole moves relative to you , even though the airplane is going in a straight line.   SAS tries to maintain the same absolute heading by feeding in more and more rudder correction, sideslipping the plane.
  • Roll - If the wings are not perfectly level the aircraft will slowly turn,  SAS tries to correct this by feeding in rudder (generating sideslip, which then tends to induce more roll) rather than by removing the roll that's generating the turn in the first place.

Youtubers   are probably making a video to demonstrate an impressive payload mass fraction or interplanetary delta V,  so their craft will not have the luxury of excessive thrust to weight.  As such they need  to be able to adjust pitch angle in 2 or 3 degree increments.

I fly low TWR spaceplanes on keyboard, i use one of two strategies to control pitch accurately - 

1.  For airplanes with non-angled wings, i turn SAS off completely in the  atmosphere and just use pitch trim (ALT S + ALT W) to control climb rate.  

You can see that during the speedrun i am feeding in nose-down trim to stop the plane climbing.   When we max out, i add several notches of nose up (alt + s) until we have an angle of attack of 5 degrees, which gives best supersonic lift drag ratio, and start the nukes.

2.  For airplanes with angled wings (built in incidence angle) I  do use SAS, but keep it locked in Prograde mode, because the wings still make lift even with the body at 0.

Note that Prograde does not maintain exactly 0 AoA in the atmosphere.   It feeds in a certain amount of nose up or nose down input to try get the plane closer to prograde,  but if the plane's aerodynamics would make it fly at 8 degrees nose up without input, then with prograde hold, this is error is reduced to maybe 2 degrees or so.      This can be used to your advantage,   this airplane uses trim flaps bound to action groups so you can adjust the nose angle a few degrees up or down from prograde -

https://kerbalx.com/AeroGav/Stretch-Ray

Note that when landing it though,  on keyboard,  I too used SAS with this aircraft.    The difference being i am not bothered about the drag created by jerky movements,  i just want it to respond quickly to corrections and hold a steady attitude when i'm not making corrections -

 

Link to comment
Share on other sites

5 minutes ago, AHeroReborn said:

Well, I think my question was answered. Continue to chat if you fell like it!:D

Notice the check marks at each post?  Click the one of the post you think it's the best answer answer.  It will mark the question as answered, which is helpful to people browsing the forum seeking or offering help. 

Link to comment
Share on other sites

Just now, Spricigo said:

Notice the check marks at each post?  Click the one of the post you think it's the best answer answer.  It will mark the question as answered, which is helpful to people browsing the forum seeking or offering help. 

I appreciate the information, thank you.

Link to comment
Share on other sites

This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...