Low Tech Spaceflight and stuff

  I posted a thing about some PC's stranded on a primitive world trying to get
to their ship in far orbit by building ssome sort of spacecraft from local bits
  I've tried to suss out the 'small step' rules in Hard Times and wondered if
this idea might work:-
		A set of hydrogen balloons lifting a small LALV fueled either
by Lox and Hydrogen OR LALV using hydrazine and peroxide
anyone want to tell me how feasible any of this might be?
Ta
PAVEWAY