Question on fuel balancing

[Isamin]

Hello folks, I made this account to ask a question on an issue I am having with my craft. Like many others I have created a craft with the same concept as the space shuttle but I am having trouble keeping the craft stable while the shuttle is being carried by the rocket. I know it is to do with fuel balance but I am unsure how to solve the problem.

The shuttle pulls the rocket on its side but that is offset by using the shuttles own engine thrust to counter. I guess this is inefficient to have the shuttle and rocket pushing against each other so if someone has a better solution please suggest.

Currently the craft is powered by the two aforementioned LV liquid fuel boosters attached to two FLT800 fuel tanks on the shuttle and a single mainsail attached to two jumbo fuel tanks stacked horizontally on the rocket itself. The fuel tanks on the shuttle need to be full once it seperates from the rocket so the jumbo tanks currently feeds fuel into the FLTs. This could also be done by pumping fuel from the jumbos directly into the liquid fuel engines, though I don't suppose it matters much. My problem is that the top jumbo empties first thus creating an imbalance. So what I would like to know is how can I get the two jumbo tanks to empty simultaneously? I am also aware that once they do both run empty that there could well be an imbalance caused by the full liquid fuel tanks on the shuttle, so how should I proceed?

Edited August 2, 2013 by Isamin

[Gus]

I have built dozens of spacecraft and all of them have been symmetric. Assymetric ships add a whole new level of complexity. I wouldn't recommend it for a beginner.

[Epthelyn]

It's not inefficient to have the shuttle pushing against the fuel tank; in fact, that's how real life works - The engines on the space shuttle are angled against the fuel tank.

Building a stock space shuttle is hard. It might be balanced at the start but, as you're finding, it will slowly change the C.O.M and tilt or do crazy aerial acrobatics and fall apart. The only way to drain two tanks simultaneously is to connect them both independently to a third, smaller, tank and keep them apart so they don't flow into each other.

|| <--- Fuel tank

_ <--- Separating object

|| <--- Fuel tank

_ <--- Separating object

|| <--- Small fuel tank

V <--- Engine

That will still eventually unbalance.

I believe other threads have been made on the subject of space shuttles. It might be worth looking for them and seeing if people had some good advice.

[TaranisElsu]

I created a mod that can help with making both orange tanks empty at the same time: http://forum.kerbalspaceprogram.com/showthread.php/25823. You can set the tanks to Balance mode, and my mod will keep them the same percentage full. It won't completely solve your issue though.

I second the recommendation to look at threads made about the subject. Also check out The Winter Owl on Youtube. He is making a series on Space Shuttles:

. That is his favorite way to play.

[Toshogu]

If you want the two jumbo tanks to empty simultaneously then all you have to do is add a fuel connector that goes from the lower to the upper. That way as the top one drains the bottom one will fill it. I use this trick for all my airplanes. All the tanks will drain evenly preventing odd shifts in COG.

No need to use mods or stupid things like that. Fuel Lines are your friends.

Edited August 2, 2013 by Toshogu