Mod to balance CG on spaceplane

[gilflo]

Hi

Does anybody knows if there is a mod balancing the fuel automatically between tanks during spaceplane flight, to keep the CG around a preset value?

It would greatly help for stability of flight, especially when flying manually and also when fuel and oxidizer are not balanced (rapier for example: jet engine for take off then rocket engine)

It would also help for design.

Thank's

[Taki117]

I use TAC Fuel Balencer, works well enough.

[BudgetHedgehog]

Nah, you'll want PWB Fuel Balancer. TACFB is good, but the CoM moves as the tanks drain. With PWB, as long as there are resources to move around and places to put them, it'll try and maintain a given CoM as much as possible.

[gilflo]

Thank you, that's exactly what I am looking for

[Vanamonde]

Moved to Add-on Affairs.

[gilflo]

Nah, you'll want PWB Fuel Balancer. TACFB is good, but the CoM moves as the tanks drain. With PWB, as long as there are resources to move around and places to put them, it'll try and maintain a given CoM as much as possible.

Well on spaceplane it looks very difficult to keep CG with PWB balancing a dozen of tanks. Balancing is not symmetrical enough and I got roll issue as well as pitch issues.

My idea was to move center of lift in flight to keep controllability.

So, I design an aircraft for space and return to Kerbol and I calculate and try the best position for CL (center of lift) at maxi take off weight, CG not moving during atmospheric climb as fuel is drained from 4 FT800 tanks, around CG, to 4 rapier engines. Fuel in other tanks is locked. Then I toggle to rocket engines.

The best position for CL give a certain gap between CG and CL. As CG moves keeping this value constant (between CG and CL) improves the controllability of the aircraft.

For return and landing I looked what was the best tanks to keep 200-300 kg of fuel I need so that the CG would not be moved to far away from the Take off CG and I determine where was the best position for CL.

The idea is to move CL as CG is moving to keep the same gap between CG an CL

Then I worked on movable swept wings attached to Adjustable rails from Magic smoke industries on each wing tip.

Here is the plane with swept wings positioned for take off at max weight:

Swept wing are at middle course, I can nearly release the control, the space plane climbs steadily.

Here is the plane with 300Kg of fuel in the forward tank, all other tanks being empty. Swept wings are in forward position. I run only on twin engine set the plane being very light.

With only 165kg left, swept wings are after middle position giving a very good controllability.

So the question is: Is it possible to make a mod that would move symmetric adjustable aerodynamic surfaces to keep the gap between CG and CL constant during flight, assuming you would have design the aircraft to get a max weight take off CG and CL at reasonable distance from low weight landing CG and CL.

Because doing this while flying is not so easy.

Edited February 15, 2015 by gilflo