The early Soyuz models also sported an external toroidal fuel tank surrounding the engines .
The early Soyuz models also meant to store extra propellant for lunar flights , but it was left empty on Soyuz 1 - 9 .
The early Soyuz models also sported an external toroidal fuel tank surrounding the engines and meant to store extra propellant for lunar flights , but it was left empty on Soyuz 1 - 9 .