Why don't you produce the hydrogen down the earth and store it in a tank on the rocket? This is a bit dangerous because hydrogen explodes but more easy to do. I have read one time about hydrogen fuel which is solid and without the danger of explosion like the gas one. Make a search in google.
no i mean an engine that fits inside the engine... like a smaller cylinder-like thing that contains h2o+nacl ... with a spiral fashion cathode and an inverse spiral anode to produce a large ammount of hydrogen and oxygen .... and all the gass exits through a small nozzle to create a jet of hydrogen where it mixes with oxygen from the same system in the combustion chamber and so explodes like a jet... with like 130hz like in jet engines
and voila...
a rocket is obtained
now my question is
can this system be made light enough so that the engine is powerful enough to lift off
100 grams? Even Estes solid fuel engines are that heavy. I doubt if you could get enough mass flow to lift a rocket, considering how much dead weight there would be in tankage and piping.
You might find a larger unit could work. A period of experimentation might be called for.