Issues with CG/thrustline for SpacePlane, how to find CG mid-flight or have differential throttle?

[GeorgeG]

I'm working up an SSTO that has VTOL capability for landing. See pics (test flight on Kerbin with gravity hacked to test out takeoff and landing in lower gravity).

I need to modify the design due to CG changes as fuel is used.

But I'll probably still need to use fuel transfer between fore-aft tanks to get the CG good enough for a vertical landing (and takeoff) with the fuselage level. What I'd like to know is whether there is some method in the game, or some mod, that can let me know what the CG is in mid-flight. So I won't have to do tedious and time wasting (and fuel wasting) fuel transfers, then throttle up with the VTOL engines and see if it pitches up or pitches down out of control, or stays steady and under control (CG close enough to thrustline). ep lane that can do a 180 in 6 seconds or less and not 60 or more. If out of control, then more fuel transfers, more tests, and so on. Really would help to not have to do the thrust tests a ship like this is ver sluggish to respond, would be different if it was a nimble little ship with the same issues. Also this one has so many parts that there is a LOT of lag, so that again is making testing tedious.

This is also a problem for re-entry as well. The only solutions for that are to keep going back to a quicksave to try different fuel transfers until it does a safe re-entry without tumbling out of control or being too nose-heaving ot fly to an accurate landing. Well, I do know that ideally I should design the ship so the CG wil not shift very much, and I am going to make some changes, but still, there are often some practical limits (this ship started out that way but by the time it got flyable due to wing and tail changes.... it wasn't anymore).

Would be great if mid-game it was possible to being up the CG and Thrustline indicators that are available in the VAB and SPH, but AFAIK that is not possible. Maybe that sort of thing will be added to the aerodynamic aircraft/ space plane upgrade in the next major update.

Is there a mod that can do differential throttling? Say if I had the engines spaced apart with a set in front of the CG and a set aft of the CG, it would throttle one set higher and the other set lower in order to keep the thrustline balanced thru the CG? I know there was something like that a couple of years ago, or so, which allowed true Space Shuttle type models to be flyable, but I do not remember the name and it may be a long dead mod.

BTW - I've been at this since version .16, though sometimes take many months away from the game. I've done a number of Space Planes, but nothing this big, trying to use VTOL

- GeorgeG

Edited January 17, 2015 by GeorgeG

[*Aqua*]

RCS Build Aid

It can display the centers of wet and dry mass in the editor. That's what you are looking for, isn't it? I mean you wrote a wall of text...

[SAI Peregrinus]

http://forum.kerbalspaceprogram.com/threads/67270

Differential throttle.

[GeorgeG]

Aqua and SAI Peregrinus, thanks. I'll try out both.

- GeorgeG