Can you imagine the stress...
Developing on that project, let alone deploying updates. Knowing that if you stuff it up untold billions (trillions?) of dollars, millenia of man-work and unique scientific opportunity could become unreachable ever again.
No matter how many levels of safeguards in the code itself, and the level of paranoia in the testing and deployment of the software... can you imagine what it must feel like sitting there with the "are you sure you want to upload yes/no" prompt in front of you?
I'm not sure I could do it. Could you?