We know when Dr Mann failed the docking procedure and Cooper and TARS try to dock on the spinning endurance by matching their rotational speed, the ship started entering the stratosphere to which Amelia Brand says "She's got no heat shields". Then Cooper tries to slingshot Endurance around Gargantua in one last effort by detaching TARS and himself towards the black hole just shy of the horizon, thereby giving Brand enough thrust to leave Gargantua's orbit. If Endurance was not built to withstand the heat generated while entering a planet's atmosphere, how was it able to withstand the heat generated by one of the hottest things in the universe? Accretion disks are believed to radiate in the X-ray part of the spectrum, which puts their temperature between 300,000K to 300,000,000K.
Here's the conversation:
CASE: It's not possible.
COOPER: No... it's necessary.
CASE: Endurance is hitting stratosphere!
AMELIA: She's got no heat shield.