Question

How fast will hydrazine boil out of a tube into a vacuum?

Answer 1

My guess is that rather quickly, the boiling action will produce a plug of frozen hydrazine in the tube. Once that happens, the sublimation on the outer face will cause condensation and/or solidification on the other face and the plug will walk back towards the tank until it either reaches it or the solid portion of the plug get to thin in which case it will burst and vent like in the beginning and start over.