Complex sentence: Despite Stone's protests, Kowalski detaches himself from the tether to save her from drifting away with him, and she is pulled back towards the ISS while Kowalski floats away to certain death.
Split into simpler sentences: Despite Stone's protests, Kowalski detaches himself from the tether to save her from drifting away with him. Stone is pulled back towards the ISS while Kowalski floats away to certain death.