The original shuttle design had pyrotechnics to separate the crew compartment from the bulk of the orbiter and parachute it safely to earth.
NASA management elected to remove the pyrotechnics and the parachutes.
In the challenger disaster, the crew compartment separated at the designed-in parting line, and the still living crew plummeted without the benefit of parachutes to a very hard impact with the ocean.
I have heard about that. That's horrific and absolutely typical government idiocy to not have a safety escape system.
I think they did have ejection seats for the first couple of flights. For the first launch the body flap was bent back beyond design limits from the pressure wave of the solid rockets igniting. John Young said if he would have known what happened at the time, he would have ordered an ejection. Such a mishap should have made the Orbiter uncontrollable on reentry, but obviously they made it.
Had management taken the Columbia foam impact seriously, Shuttle Atlantis was already on the launch pad and could have done a rescue.