Plane-part to control center-of-mass through fuel

[Kegereneku]

After a brief research I haven't found similar idea here.

It came to me looking at that plane from the beta-tester that it can be hard to keep the center of mass right in space-plane

So I'm suggesting the idea of a ASAS-like part which would either :

- use the fuel transfer mechanism

- or select which fuel-tank to drain from first

...in order to keep/move the center of mass roughly...

- where it was at first (following the logic that usually try to have the plane stable at takeoff.

- or where you want through tweakable (I think we could start with just ONE slider for the longitudinal axis)

Possible evolution :

- becoming part of a new fuel-control UI

- shifting the center of mass three-dimensionally

- might be useful for big spaceship

Expected issue :

- Not all fuel tank can be expected to be interconnected in a plane, especially if you built the plane to refuel station.

- Any staging/docking would necessitate to reset the system

- I don't really know how to make such feature easy to use for plane and rocket through tweakable

- Unlike the ASAS it would be constantly "on"

That's all.

[ximrm]

I'm not sure, but I think that problem could be solved with the TAC Fuel Balancer(and maybe vesselview). (which ought to be implemented into the game imho)

-Shifting the mass three-dimensionally wouldn't make too much sense for planes as the fuel tanks are rarely stacked upon each and mostly spread laterally.

-tweakables don't make much sense in flight, but there could be a button(if there's a fuel manager available) to tell that part how to behave.

Please excuse my ignorance but I really don't see a problem here that couldn't be solved with TAC.

[NWM]

Sometimes balancing is difficult even with TAC too /without - impossible/

- some extra ideas: unifying stacked tanks - they works as one

- scheduling the consumption 1.,2.,3., and so on...

[Red Iron Crown]

Something like Goodspeed Fuel Pump's implementation might be better. It's a bit more difficult to get the hang of than TAC FB, but is much more flexible (though it makes fuel lines redundant).

Though either of them struggle with keeping tanks filled proportionally rather than just all filled to the same percentage.

[Wanderfound]

While I'm not disagreeing that making it stock would be a good idea, there are a few solutions at the moment.

As mentioned, TAC-FB and Goodspeed. Goodspeed is the better of the two; the only problem with either of them is that they make fuel lines redundant and remove some of the engineering challenge when building. And designing on the assumption that Goodspeed/TAC-FB will handle things makes the design dependent on those mods, which can be a problem when sharing designs.

As for the engineering solutions:

* Spread your fuel load laterally around CoM rather than longitudinally. Getting CoM to dCoM offset to <1m isn't too hard.

* Arrange your fuel lines to make the tanks drain in the order you choose. On multi-engine planes, I normally have forward-mounted lines running from the lateral tanks to the core, and rear-mounted lines from the core to the lateral engines. This makes the tanks first drain from rear lateral to forward lateral, then forward core to rear core. The CoM stays roughly centred throughout, and any weight shift is initially towards the nose, avoiding the "CoM behind CoL" issue.

* Use right-click tweakables to lock off the fuel flow from a forward tank. This will stop it draining prematurely, as well as enabling you to designate a tank as "emergency reserve". You can fine tune this by doing things like locking off LF but not O on certain tanks.

[Bilfr3d]

Rather than having a whole separate part for this, I would think that it would be more logical to have it as a module that is included in the cockpit part. After all, that is where the astronauts control the fuel flow. If you REALLY wanted, you could than make some parts and tack that module onto the part. Apart from that, I like the idea and would definitely like to see it implemented.

[DundraL]

Rather than having a part that manages fuel balance, you should search for a more permanent way to balance your aircraft and then put main fuel tanks near the center of gravity. While TAC fuelbalancer does what you want, in the end, an empty aircraft will still be unstable if you rely on fuel to keep your craft balanced.

IMO, the problem isn't fuel weight, its that there's nothing that scales with craft size other than engines and fuel. And one of those disappears throughout the mission, leaving heavy engines at the back with nothing to balance them out.

http://forum.kerbalspaceprogram.com/threads/92819-An-arguement-for-a-quickfix-in-the-spaceplane-patch

My solution was to transfer some weight to intakes from engines, but I never got any responses. :/ Add a reply if you think its worth anything.