On controlling fuel flow

[fireblade274]

When flying my SSTO, I find my self frantically un-checking fuel tanks i've blocked off liquid fuel from, so my jets wont use that tank for their power and use the one I want them to use. But is there a better way to toggle a fuel tank as "on" or "off"? I've tried linking the tanks to action groups, but it doesn't work.. It would be really nice if it did though. Is there something im missing?

If I could shut on/off access to multiple tanks at once that would be fantastic

[Wolf Baginski]

There are a couple of Action Group mods that give more groups, and might give extra functions.

Jets/air-breathing mode takes fuel from all tanks including radial attachments. Rockets take fuel from the "furthest" tank, and need either a fuel pipe or a Mod for radial attachment.

Dual-mode engines such as the RAPIER can do odd things.

You can still manually control fuel/oxidizer transfer in flight. If you can get into orbit you have plenty of time to transfer fuel.

I routinely use the CrossFeedEnabler Mod so that all my SSTO vessels can use all their Fuel. Then I have a fuel switcher to keep Oxidizer where the rockets can use it. This can also help with CoM and the stability. Check for the KSPI mod: I think that has all you need for that.

It's easy to think you need a lot of Fuel for the jets, and have too little oxidizer for the rockets, With the jets using fuel from all tanks, you might need a small fuel-only tank in the main stack that fuels the rockets to compensate.

My first really successful SSTO didn't use radially-attached tanks, and did have a small fuel-only tank, well forward, It helped with the fore-and-aft trim for reentry

[Red Iron Crown]

The Rapier in closed cycle mode is the exception to the "rockets take fuel from the furthest tank" thing, they draw LF and O in the same way that airbreathers draw fuel.

One method to protect fuel from the greedy engines somewhat without disabling the tanks is to connect the tanks you want saved to the rest of the vessel through a decoupler (even if you don't plan to decouple them), then making one of those tanks the root part. The engines will think the rest of the vessel is a drop tank and drain its tanks first, though it will start draining the payload tanks when the others run dry.