If Penny is not rescued, or if Joseph becomes upset through dialogue, entrance through Murder Pass will be the only option to get to Vault 87.
The Lone Wanderer must have a Science skill of 50 to hack the terminal to get into the Vault.
Joseph can be found in the Little Lamplight schoolhouse in the morning. How do you get into Vault 87 without dying? The super mutant behemoths are the result of extreme growth, and stand at roughly 20 feet tall, though some sources report specimens up to 30 feet in height.