per most tv/movie shows shields are lowered unless combat looms (probably so the captain can spout those overly dramatic words " raise shields" thus informing the audience in its infinite intellegience that Violence will now commence (oh no hide the wimmin n chillin)
however justification is usually that the shields interfere with scientific sensors and are a major power drain
what i dont like is that we dont have a small (i'd say hardcode to max at 25%) settable chance to detect mines before we run over them i mean come on them scientific super sensors etc should be good for something right
Those sensors are present. They are called "Minesweeper V."
An alternative is to remove the cloaking ability from the mines. Maybe then add cloaking devices for mines, which depend on tech like normal ones do. Now, you get a nice mine cloaking vs. detection arms race.