[Dylan16807]

Light has effective mass. It's well known that you can shoot light in one direction for a tiny amount of thrust the other way.

The device under consideration is special because if it works it is a reactionless drive. Nothing is coming out of it.

[triplepoint217]

Light actually has momentum but not mass. Calling it effective mass isn't far off, but sometimes my pedantic physicist kicks in.

[Dylan16807]

The proper term I'm used to is "relativistic mass", but I didn't want to make the discussion complicated. Would you not phrase it that way?