Herrick: Thanks Chris. I saw a couple of buildings with locked doors but I didn't want to attempt to break into them because I thought there might be a nicer way of getting in. Is shooting through the doors the only way to get into these places? I don't have any powerful upgrades and I don't want to get killed by sentinels.
wizisi2k: if you don't have the boltcaster, the only way in is to bash the door down. You'll find suprises in there... IF you pick the right one and while bashing expect sentinels to attack you ~4-5 times until the door is down.
All right. I'll use the Boltcaster.
ChrisTheS: The tutorial tells you shoot them, so I don't know if there's another way. I got through the first one by shooting the door a bit, running back to the ship and circling the area until the sentinels forgot about me, and then coming back two or three times. The second time I just took the door down as far as I could before they started shooting me, blew them all up, went back to the door and managed to get it open and inside before they started shooting me again (they don't track you inside buildings).
The third time they killed me because I ran out of ammo :P. But I always go to the save point before doing anything at a site, so recovering my inventory wasn't a problem.
I must've missed that tutorial message. I'll give it a try, thanks.