Hi, Can someone double check I understand this correctly? The turbofan has lower specific fuel consumption because a gas's momentum is proportional to its velocity, whereas a gas's kinetic energy is proportional to its squared velocity. Therefore a turbojet can be made more efficient by adding a bypass stage, which effectively removes some of the jet's velocity (via a turbine powering the fan), removing some of the momentum (and therefore thrust), but removing also a much higher proportion of kinetic energy. If this kinetic energy powers the front fan, then it can be added to the slower moving inlet air, which increases its speed and therefore the bypass air gains disproportionally more backwards momentum than was lose at the jet. The net impulse on the air is therefore higher for a given amount of fuel. Is this correct? It's a "slow the fast thing down and use the energy to speed the slow thing up" idea? Do pressure ratios come into it as well? Cheers.