The naked crew are forcefully strapped into the chairs by their alien captors. They moan uncomfortably as their assholes are guided around smoothly pointed steel rods. Metal collars go around their dainty necks, and shoulder guards keep them from moving an inch.

The chief Engineer is proven right, much to her own chagrin. The collars begin to rise one by one, at first merely choking the girls… Then slowly as their throats stretch beyond what is natural there is a soft popping sound as their vertibrae are painfully dislocated

Necks snap, and soft tissue tears.
Their piss and shit are collected by the bowls under their asses and disintegrated by plasma fields.

The chief Engineer watches on as the stupid Ensign's neck snaps, and then nervously fidgets as she feels her own collar begin to rise.