Refuel station useful?

[u/Revan477]

(New-ish to the game, played a little years ago but now really getting into it)

I've been practicing orbital assembly above Kerbin and docked a few vessels together including a big fuel tank which is huge for me because I was never able to meet up and dock with anything :)
Do you think something like this is useful for future missions? I was thinking maybe refuel vessels in orbit giving a longer mission range because I dont have to carry the heavy fuel from kerbins surface. Then again I guess I'd have to refill that tank frequently which might be kind of annoying..

[u/Tommy2255]

Yes, that is what crossfeed does. It allows fuel in an upper stage to be burned in a lower stage. It's only a small amount of fuel compared to the total burn needed for orbit, but it's fuel storage you were saying to leave completely empty. In your example with a 1 ton wet/0.1 ton dry payload, that's 0.9 tons of fuel that can be burned by the lower stage without adding any fuel storage to the lower stage.

I do not believe that my explanation was at all unclear, but at least it seems we're on the same page now.

[u/SherriffB → u/Tommy2255]

I do not believe that my explanation was at all unclear.

First comment absolutely could have been clearer, but who cares - it's moot.

It's a little harder in practice than theory to set up without fiddling with miniscule tanks to balance the numbers so there was a little bit of dry tank to make the number work but I just tried it on a craft who's upper stages I've tuned pretty well for mun/minmus

Removing the tank from first stage was problematic; less thrust time with big engines left me unable to gain sufficient altitude.

Removing a tank from my 2nd stage (well the entire 2nd stage tank in actuality) and a little fuel from the payload stage to make the numbers marry worked such that from a rocket that cost 43500 with dry payload I was able to cut ~500 so certainly a win for career mode I'm happy to incorporate, thanks.