CSTS
Crew Space Transportation System (CSTS), originally Advanced Crew Transportation System (ACTS), was a proposed design for a crewed spacecraft for low Earth orbit operations such as servicing the International Space Station, but also capable of exploration of the Moon and beyond. It was a joint project between the European Space Agency (ESA) and the Russian Federal Space Agency (Federal'noye kosmicheskoye agentstvo Rossii – FKA).