Vecrtoring and Thuds, or Lack Thereof

[Corona688]

They make a bit show of moving around, but any craft I build with them doesn't actually feel vectored forces from them!  Is it just me?

[Reactordrone]

Just tested a ship with no other means of directional control and they seemed to work fine.

[Geonovast]

Typically the only reason I use thuds is to give launchers vector control when their main engine doesn't have it, say if I'm using a clusters of reliants on the first stage.

So it would seem something is wrong on your end.

[Fraktal]

Sounds like the Thuds are giving your rocket insufficient torque. How many fins do you have at the end of the rocket? Too many will make the rocket excessively stable and hard to steer.

[Corona688]

I managed to answer my own question...  In rebuilding one of my ow designs I forgot an important bug that apparently still exists -- thuds above the COM will respond backwards (or rather - won't respond backwards, when they should), so you better disable their gimbals.

Now that half the engines aren't fighting the other half it responds fine.

This is the craft being recreated, a twisted-candle asparagus lifter:

Edited October 17, 2020 by Corona688

[Corona688]

On 10/17/2020 at 10:27 AM, Corona688 said:

I managed to answer my own question...  In rebuilding one of my ow designs I forgot an important bug that apparently still exists -- thuds above the COM will respond backwards (or rather - won't respond backwards, when they should), so you better disable their gimbals.

I have pinned down this issue more exactly.  At launch, they respond as they should, but as the COM moves, they continue responding as before, until the next stage change.  In extreme cases, they can respond backwards!

This might not be a bug per se.  I'm not sure they are intended to compensate for that.  It's something useful to know when designing asparagus.

Edited October 22, 2020 by Corona688

[Snark]

On 10/17/2020 at 12:27 PM, Corona688 said:

This is the craft being recreated, a twisted-candle asparagus lifter:

As pictured, you've got your Thuds kinda in the middle of the rocket, meaning they don't have much lever arm to work with and I'd expect their thrust vectoring to have considerably less effect.

If you want them to have lots of effect on steering the sihp, then you'd want to put them way down at the very bottom of the rocket, i.e. as far behind the CoM as possible, to give them a decent lever arm to work with.

(No criticism of your design is implied-- it may make perfect sense, in terms of staging for the twisted-candle asparagus.  Just that it's not very friendly for thrust-vectoring.)

[Corona688]

On 10/24/2020 at 11:08 AM, Snark said:

As pictured, you've got your Thuds kinda in the middle of the rocket, meaning they don't have much lever arm to work with and I'd expect their thrust vectoring to have considerably less effect.

That is not true at the time I have a problem.  This is a multi stage rocket