I know that photons hitting a solar sail can add energy to that sail. I know that photons are gauge bosons. I know that gauge bosons are thought to be the carriers of fundamental forces. If a solar sail were gaining speed to a point where it reached relativistically with respect to the power source, I know that an observer on a solar sail would observe a reduction of the force on that solar sail. Is not the same essentially true for any massless gauge boson? It seems that the work done on the sail by previous photons reduced the amount of work that future photons coming from the same source and direction could add to it, that is, from the frame of reference of the sail. It would seem that the actual amount of work done on the sail, from the frame of reference of the sail, would be less than the energy expended by the source which produced the photons. Is this all correct?