Help debugging my first orbital attempt in RO?

[BenKerman]

Hi,

Without sharing any videos or screenshots (I could share if needed), I have a problem with my first orbital attempt in RO.  It seems my first stage shuts down prematurely.  I can figure out why this is happening -- it's because the calculated apoapsis matches the orbit altitude target I entered in MechJeb (170 km in my case).  I don't want that to happen; is there a way to force a stage to use all of its fuel?

Second, just before the engine shuts off, the engine gimbals, and so after the engine shuts off, my ship is put into a tumble about one of its short axes.  This is very annoying.

What can I do to solve these problems?  I want to use all of my fuel and I don't want the ship to tumble after the engine turns off.

 

Thanks,

Ben

[BenKerman]

Well, I got my first satellite to orbit around Earth in RO.  Some keys were to make sure my avionics didn't have excess batteries (they did), and also to use Smart A.S.S. instead of Ascent Guidance.  Thanks!

[Aelfhe1m]

In RO, MechJeb ascent guidance works better with primer vector guidance (PVG) rather than the classic ascent guidance. For early rockets you generally don't have any coast phases (which classic relies on) but PVG is designed to handle continuous burn to orbit and in the recent versions can even handle unguided SRB kick stages.

For example, this is the first orbital rocket I used in my latest save. It has a RD-102 first stage, XLR-11 second stage and two GCRC kick stages. With the MechJeb settings shown in the image, it flies itself to orbit (provided test flight doesn't fail an engine).