A hydrogen generating apparatus comprising: a housing; a liquid fuel bladder containing liquid fuel; a reaction chamber within the housing and having sidewalls and a hydrogen-permeable liquid-impermeable membrane to allow hydrogen to leave the reaction chamber into the housing while restricting liquid and/or paste-like reaction by-products to an interior of the reaction chamber; a liquid fuel conduit including a starting mechanism and connecting the liquid fuel bladder to the reaction chamber; and an actuator to compress the liquid fuel bladder to force liquid fuel through the liquid fuel conduit into the reaction chamber; the housing including: a hydrogen outlet including a valve to connect the hydrogen-generating apparatus to a fuel cell or other hydrogen consumer; a relief valve to automatically vent hydrogen gas to atmosphere if pressure within the housing reaches a trigger pressure; a reference pressure vent; a solid fuel component contained within the reaction chamber for the dissolving of the solid fuel by the liquid fuel component to form an aqueous fuel mixture; a reactor buoy contained within the reaction chamber, the reactor buoy comprising an elastomeric chamber connecting a first end cap to a cup and a second end cap, or the elastomeric chamber is integral with the cup and connects the first end cap to the second end cap; a hollow tether fluidically connecting the elastomeric chamber to the reference pressure vent so that pressure within inside the elastomeric chamber is atmospheric or another reference pressure; and a catalyst disposed within the cup, on the elastomeric chamber, or on the first end cap; including a hydrogen consumer attached to the housing covering the relief valve to convert excess hydrogen gas that would be vented to atmosphere into water or an inert compound; wherein the reactor buoy is configured to open the first end cap and the cup when the pressure inside the housing is less than or equal to the pressure in the elastomeric chamber to allow the aqueous fuel mixture in the reaction chamber to contact the catalyst, and to close the first end cap and the cup when the pressure inside the housing is greater than the pressure in the elastomeric chamber to seal the catalyst away from the aqueous fuel mixture in the reaction chamber. a housing; a liquid fuel bladder containing liquid fuel; a reaction chamber within the housing and having sidewalls and a hydrogen-permeable liquid-impermeable membrane to allow hydrogen to leave the reaction chamber into the housing while restricting liquid and/or paste-like reaction by-products to an interior of the reaction chamber; a liquid fuel conduit including a starting mechanism and connecting the liquid fuel bladder to the reaction chamber; and an actuator to compress the liquid fuel bladder to force liquid fuel through the liquid fuel conduit into the reaction chamber; the housing including: a hydrogen outlet including a valve to connect the hydrogen-generating apparatus to a fuel cell or other hydrogen consumer; a relief valve to automatically vent hydrogen gas to atmosphere if pressure within the housing reaches a trigger pressure; a reference pressure vent; a solid fuel component contained within the reaction chamber for the dissolving of the solid fuel by the liquid fuel component to form an aqueous fuel mixture; a reactor buoy contained within the reaction chamber, the reactor buoy comprising an elastomeric chamber connecting a first end cap to a cup and a second end cap, or the elastomeric chamber is integral with the cup and connects the first end cap to the second end cap; a hollow tether fluidically connecting the elastomeric chamber to the reference pressure vent so that pressure within inside the elastomeric chamber is atmospheric or another reference pressure; and a catalyst disposed within the cup, on the elastomeric chamber, or on the first end cap; a hydrogen outlet including a valve to connect the hydrogen-generating apparatus to a fuel cell or other hydrogen consumer; a relief valve to automatically vent hydrogen gas to atmosphere if pressure within the housing reaches a trigger pressure; a reference pressure vent; a solid fuel component contained within the reaction chamber for the dissolving of the solid fuel by the liquid fuel component to form an aqueous fuel mixture; a reactor buoy contained within the reaction chamber, the reactor buoy comprising an elastomeric chamber connecting a first end cap to a cup and a second end cap, or the elastomeric chamber is integral with the cup and connects the first end cap to the second end cap; a hollow tether fluidically connecting the elastomeric chamber to the reference pressure vent so that pressure within inside the elastomeric chamber is atmospheric or another reference pressure; and a catalyst disposed within the cup, on the elastomeric chamber, or on the first end cap; including a hydrogen consumer attached to the housing covering the relief valve to convert excess hydrogen gas that would be vented to atmosphere into water or an inert compound; wherein the reactor buoy is configured to open the first end cap and the cup when the pressure inside the housing is less than or equal to the pressure in the elastomeric chamber to allow the aqueous fuel mixture in the reaction chamber to contact the catalyst, and to close the first end cap and the cup when the pressure inside the housing is greater than the pressure in the elastomeric chamber to seal the catalyst away from the aqueous fuel mixture in the reaction chamber.