Silent Running

A procedure where a ship approaches a target with no burns (i.e. no deceleration or acceleration) and with all systems shut down to a minimum. In such circumstances a ship is virtually undetectable until it gets within active radar range - around 500-1000km.
During this time it has to rely on precise positioning and navigation, and because it cannot decelerate it has to approach very slowly - making SR approaches unusual except in small local tactical actions.

Silent Running from the M25

Interstellar ships routinely enter from the M25 at velocities of several billion kilometres per hour. This is why they have to decelerate fiercely for many days to arrive at a planet at a useful velocity. Silent running ships are not decelerating, so their entry speed has to be low enough that they can dump the velocity in the last few hours of approach. This means that in a silent running approach the entry velocities must be several orders of manitude slower than normal.
At those velocities it can take years rather than days to transit from the M25 to the colony world. The later you leave the final decelerating burn, the slower the ship has to be going to start with, and hence the longer it will take to travel the distance from the M25 to the planet.

Click here for a handy ready reckoner for silent running times outlink