The Tug Module (Medium) is one of the only two maneuverable medium stages in the game; the other one is Orion Service Module. In sandbox missions, it can be your best companion. It is unlocked at a very early stage in the career missions, and it has been proven to have enough fuel capacity to carry most payloads to any planet, and entering its orbit. It also has the ability to carry multiple payloads at once.
It holds two batteries which are in-built and can't be swapped, and is automatically ejected from the payload and disappears as soon as the payload is docked to something else while in space, which makes it less useful as a builder tug.
Also, it can't be docked by itself. It uses 9 units of Power in the game, and generates around 152 units, however the power can't be transferred to another module as it is not dockable.
For Multiple Payloads, use this launch configuration: Tug Module (Medium) -Payload - N1 Rocket Fairing - Payload -Fairing
Tug Modules can be hazardous in space station assembly or resupply missions as it will eject automatically as soon as the payload is attached. Once it is ejected, there is only a second to select it and control it, until it disappears some distance away.
During the time of ejection, it can hit any nearby space station parts and send it rotating,or off course,and at the worst case scenario, explode.
To avoid this, players can immediately go to the objects menu after ejecting the Tug Module and delete the Tug Module. Its name will be "Tug".
Like all parts that are manoeuvrable, if spun too fast it wil explode and destroy anything attached to it.