Graphic of Exodus Class saucer separation.
The Saucer separation is used in two conditions:
1. The general scenario of battle conditions and civilians need to be evacuated. Please note that even in this scenario the saucer section is not only warp capable, but also contains a Bat class vessel in case a second saucer separation scenario arises.
2. The Mjolnir class is also used to taxi other non-transwarp capable starships. The transwarp section might be detached for an independent transwarp mission.