The arguably less time consuming method is to buy or find security cards -- they come in different colors, and different color cards can open different colored security doors. Some cards open more than one type of door. The details behind that I'm unsure of, but I was able to open pretty much everything with law and maintenance cards. Once you've got the card in your inventory, you just walk through the security doors like you would any other door.
The arguably more time consuming method is to somehow destroy the door, either by bashing it down via weapon or hitting it with something like acid (fire, etc.). You can only do this fairly reliably if you've got decent strength (and a fair penetration weapon) or access to the necessary utilities. MK I acid grenade is perfect and cheap to tinker, but runs the risk of destroying something valuable on the other side of the door... like a square with four lockers in it (muttergrumble
).
The least time and resource consuming method is to knock the door out of the way, either via force bubble/bracelet or explosive effects (HE grenades, missiles, etc.). About the only way that can go wrong is if you push the door on
top of something valuable (grumblemutter
). Certain mutations (phasing, teleportation, theoretically space-time vortex, but that's
probably not going to get you behind the door.
A door, maybe, but probably not th'one you where aiming for.) allow you to bypass them.
My favorite way to get around the doors, though, is to do just that. Through the wall, metaphorically yelling
"OH YEAH" as you tear through the apoco-crete. Acid or burrowing claws is the quickest way. Hitting it with a hammer (/other weapon) until the wall falls down works, too.