>> reporter: with more than 300 single points of failure and each one could prove to be fatal to the mission's success. >> we wouldn't have built a telescope this big unless we needed to. you have to if you want to look at the dimmest galaxies in the universe. >> reporter: webb will be launching on a european rocket from french guyana. a nod to the french partners. but getting here has cost nearly $9 billion more than initially projected and it's about a decade overdue. was there ever a moment where you thought, man, i just don't know if this is going to happen. >> there were numerous existential crises both technical and programmatic through the life of the mission. but i guess we're all eternal optimists. and we persevered and made it happen. >> reporter: kristen fisher, cnn, washington. the cnn film "the hunt for