ODSY drive, contemporary drives and Reapers
The Reapers are technologically superior to the organic species of the galaxy -- but the degree of that superiority is a matter of debate in the intelligence community.
The Reapers' thrusters and FTL drives appear to propel them at more than twice the speed of Citadel ships. Estimates of their location in dark space suggest they can travel nearly 30 light-years in a 24-hour period.
- Mass Effect Codex, excerpt of Reaper Capabilities
Pondering over how fast the ODSY drive is, I began to dig into the codex and crunch some numbers. We were not told how fast FTL travel really is until Mass Effect 3 came and pegged the organics’ ship tech vaguely to being less than half of 30 light-years a day of the Reapers’ top speed.
So, how fast do Systems Alliance et al fly? Mass Effect Wikia noted in their FTL article it to be “dozen” light-years, but I was not able to find any backing up evidence in the codexes, save for the codex excerpt I’m using.
Let’s put the fork between contemporary Milky Way FTL drive speeds between 7.5 and 12 light-years a day. That should give us a good range of less than half of Reaper velocity.
The distance from Milky Way to Andromeda galaxy is 2 500 000 light-years. Andromeda Initiative states that the journey will take 600 years.
ODSY thus covers the distance of... 2500000/600=4166,67 light-years in a year.
In a day it would cover... 4166.67/365.25=11.41 light-years in a day.
That would be going into the upper bracket of projected contemporary drive velocities! Internally consistent!
What about the Reapers then? We know the light-years/day but we need the light-years/year now.
30*365.25=10957.5
Nearly 11 000 light-years in a year! Reaching Andromeda would only take then... 2500000/10957.5=228.15 years. Reapers could’ve gone to Andromeda and back in one extinction cycle’s span easily! Fortunately for us, their creators never programmed them to extend the “life preservation” program to other galaxies.
I find these numbers internally consistent and thus am content with them. ODSY represents a revolutionary step in drive technology, in which denizens of the Milky Way become capable to cross dark space similarly to Reapers, but not as capably as them.
TL;DR
Contemporary space drive velocity: 7.5-12 ly/d
ODSY drive velocity: 11.41 ly/d or 4166.67 ly/a
Reaper drive velocity: 30 ly/d or 10957.5 ly/a
