Science is the continued investigation of what is and isn't possible. It relies on logical deduction and evidence to come to those conclusions. When it has no supporting evidence its default position is "we don't know". Science is not arrogant, the arrogance is in those that keep claiming the impossible IS possible WITH NO SUPPORTING EVIDENCE.
I think there are people who have already done it, if Ben Rich and others are to be believed, but it's just classified. I am not sure why that is exactly, but it could just be the sensible desire of preventing hostile powers from getting their hands on this technology.