Complex sentence: Its name was cognate with that of the US Project Mercury, although the shape of the capsule was very much like that of the Command Module of Project Apollo; though it was completely different inside, it also could carry a crew of three.
Split into simpler sentences: Its name was cognate with that of the US Project Mercury, although the shape of the capsule was very much like that of the Command Module of Project Apollo. Inside, Merkur was completely different from the CM, though it also could carry a crew of three.