A much smaller OTV, moving only one container at a time, but with, overall, the same capabilities as the large one. About 30 would be required to equal one of the larger ones.
A very large solar powered orbital transfer vehicle. Those little tanks in the close up are 15 ton modules flown up by the Skylon space plane. This ship takes a number of containers and moves them from lower Earth orbit to a space station at the moon L2 Lagrangian point.