Even with MechJeb my rocket is too powerful and ends up overshooting the ascent path

[grondilu]

Hello,

I was hoping getting MechJeb's ascent guidance module would help me automate the launch but I can't quite follow the ascent path.  Seems like my rocket is too powerful so I've tried to limit throttle and/or acceleration during ascent but it's very clumsy and it usually works poorly.

http://steamcommunity.com/profiles/76561198276590575/screenshot/499154497084905198

 

Is this a rocket design flaw or are there smarter parameters in the ascent guidance?

 

Edited July 10, 2016 by grondilu
wrong image link

[Streetwind]

It could also be a control authority issue - in other words, you ask the rocket to turn faster than its steering systems are physically capable of executing.

In your MechJeb control panel, you have set the turn start for 3.5 km or 100 m/s. Try lowering this. I'm not sure which of the two is hit first, since I don't know your rocket, but 3.5 km is pretty high, so I'm guessing that it's speed. Try setting it to 75 m/s or even 50 m/s.

This will cause your rocket to start the turn sooner, which does two things: first, it has more time to turn over, since it starts lower down. Second, it will naturally tend to tilt over faster, since it is going slower at the time, which removes the need for strong steering input.

Edited July 10, 2016 by Streetwind

[Foxster]

  On 7/10/2016 at 2:23 PM, grondilu said:

Hello,

I was hoping getting MechJeb's ascent guidance module would help me automate the launch but I can't quite follow the ascent path.

 

Expand  

Does that really matter to you though? Can you stall make orbit OK?

[bewing]

I agree with Foxster. Maybe, just maybe, if you followed that ascent path perfectly -- you might save one entire unit of fuel! Maybe.

[N_Danger]

 Try playing around with the angle of attack parameter. I notice you have it set on 5 degrees. Try increasing it.

I use the ascent guidance in MJ a lot but you got to keep an eye on it as it can do crazy things depending on what you allow it to do. I personally don't let it stage or deploy anything.

[dangerhamster]

As you seem to be ok to get your desired orbit (Ap is at 75k) why worry about not following the ascent path in the diagram? Have you tried manually flying the profile you want to see what happens?