[rob74]

Without being too familiar with the subject - another commenter referred to the "swiss cheese model": the O-ring design, the temperature etc. weren't the single cause, they were contributing factors, and the more contributing factors you eliminate, the more certain you can be that you won't have a repeat accident. AFAIK there weren't any more Shuttle launches at such low temperatures after that anymore either?

[pfdietz]

That's right, the accident launch was by far the coldest. They also added joint heaters.