Complex sentence: Hermes was a proposed spaceplane designed by the French Centre national d'études spatiales (CNES) in 1975, and later by the European Space Agency, which was superficially similar to the US X- 20.
Split into simpler sentences: Hermes was a proposed spaceplane designed by the French Centre National d'Études Spatiales (CNES) in 1975, and later by the European Space Agency. It was superficially similar to the US X- 20.