Does anyone know where in Article I, Section 8 of the US Constitution does the federal government find its authority to run a multi-billion dollar space agency?
8. To promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries:
Sure. It's right here in Clause 1:
"provide for the common Defence"
Probably in the same section that authorized the Air Force.
Oh, I don't know. Perhaps the same place they found authorization to run a multi-billion dollar air force? What -- you mean there's no air force clause in Article I, Section 8, but only a reference to "land and naval forces?" Begone, USAF!!!! Begone ballistic missile defense. Begone ICBM capabilities!!!!
(PS: I think one would place such things under the "common Defence and general Welfare of the United States" clause.)
You cite the article that outlines the powers of Congress. NASA is an Executive Branch agency.