I think it is impossible for space travel to ever be completely safe however it seems to me that NASA like any other company has a lot of bureaucracy. We live in a world where we want to see results, NASA would be considered to be failing if the delayed the launch of their shuttles yet at the same time launching them before all checks have been carried out is dangerous. Space exploration is one of the most visual and highly followed forms of scientific research and this puts pressure on NASA to perform to achieve its funding. I think Challenger illustrated there was something wrong with the way NASA worked and I think but can't say as confidently Colombia illustrated this hasn't changed. We can see NASA being painstakingly careful on this mission however the chances are they will once again become lax. When there is an accident it is widely reported so to convince the public space travel is safe NASA have to perform to a safety record superior to other forms of transportation and this requires they are always painstakingly careful despite the costs or make a choice as to how much a human life is worth.

On a scientific view point it is often argued that sending man into space serves little at the moment, we have been to the moon and explored it and can't yet reach Mars. However sending man into space captures peoples imaginations and hearts and maybe shows in some way the point to science to the general public (after all what could you use something like a transistor for :p). It has been argued the money could be better spent sending unmanned missions deeper into space. Personally I think human exploration is important because it is still uncertain what will be found and I think humans can explore in a more thorough manner. Either way I wouldn't like to put my life into the hands of an organisation that crashed a probe into Mars because one side worked in metric and the other in imperial.