After building a rocket based of the mercury redstone I noticed that RCS thrusters use way too much fuel than they should. The reason I say this is because on the real life mercury capsule 2 tiny helium tanks are enough to fuel the RCS thrusters for the entire mission but in game they can't even perform the first capsule turnaround after reaching space (I set the power to 5% both of the RCS thruster have around 3 small gas tanks).