I think in the opening the door only opens if you grab rocket launcher. I grab armor and plasma rifle as well but I'm sure the armor could be skipped.

This map took me a minute to figure out how it works, you have to kill all 3 spider masterminds to get the end screen. Annoyingly, the end screen can take 3-4 seconds to pop up and I'm not sure exactly why. This run the end popped almost instantly but my spider fights definitely could have been faster. The first spider can easily be killed in 2 shots and I used an extra shot on the second spider after he died.

My next fastest run was a 48.40