A vehicle including at least one bladder for containing a two-phase liquid-gas fuel at a predetermined pressure, with a bladder outlet arranged to releasing vapor fuel from the bladder. The fuel provides energy for propulsion of the vehicle, and the vapor pressure of the fuel provides initial structural integrity of the vehicle, by rigidizing and stiffening the beam assembly to resist inward buckling until the liquid fuel is expended. In an exemplary embodiment, the vehicle is an unmanned aerial vehicle. A combustion chamber and thermoelectric conversion module can generate electricity for a propeller and battery.