So this never has happened before, and I got KSP about a week after 1.0 came out. Never before had I experienced constant slow frame rate. I have had low frame rate before when firing massive rockets off, but not like this.
I accidentally deleted a (and my only) save file in the game, so I had to restart. When I created a new game, as soon as I loaded it, it was very laggy. I was around 18 fps. I went to build a rocket, and launched it. It was literally the smallest, most basic rocket you could build. When it launched, I was running at 15.5 FPS. I kept playing, hoping that it would stop lagging out, but it didn't. I got some more parts, made a slightly bigger rocket, and entered orbit. I was on my last stage with a little fuel so I could get back, and I was running 12.2 FPS. That never has happened before, and I don't know why it is happening now. I tried quitting KSP and relaunching it, still did it. I quitted Steam all together, relaunched it, opened up KSP, and it still had terrible frame rate. I don't know why this is either. There are no mods in the GameData folder, and no other save files. I didn't recently download any giant games or software onto my computer either.
But the strange thing is, when I zoom out enough so my spacecraft isn't in view, it can run at up to 62 FPS. If the sun is in my view I can get speeds of 33 FPS. When I am in map view, most of the time, it ran about 66 FPS. It seems only to go really low when you can see my craft. Why is this happening.
My Computer Specs:
MacBook Pro - 13 inch late 2011 (yes I realize it is an old computer but like I said, it was running amazingly before).
OS - 10.10.5
Processor - 2.4 GHz Intel Core i5
Memory - 4 GB 1333 MHz DDR3
Graphics - Intel HD Graphics 3000 384 MB