Hahaha what makes you so sure that Aurora exists? This could go on forever
I agree there is no definite proof. So we have 3 things to ponder.... God, UFOs, and Aurora
Let's review the possible causes as to why the Aurora line item appeared one year and then was omitted the next?
1) A mistake that was subsequently corrected. (Highly unlikely)
2) Aurora was what people thought it was, but they simply ran out of money or officials decided it was a waste of money. (more likely)

This scenario is hard for me to buy. Why would an appropriation of money be made to study exotic military apps and then cut off so hastily?
One year on the budget before suddenly realizing it's completely worthless and cost-ineffective?
3) Aurora was never what people thought it was. (more likely)
4) It was leaked in some sort of psychological ploy. (more likely)

Give the audience what it wants. They want a conspiracy? They want a secret? Give it to them. Then every "x" number of years come clean
with a project so everyone can say "I told you so!" i.e. B2-Bomber. Such "secret projects" would serve as cover for something that was Above
Top Secret!
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I'm currently reading a book called "Alien Rapture- The Chosen." It was co-authored by a Edgar Rothschild Fouche who claims that an SR-75 replaced
the SR-71. This replacement hypersonic craft attained altitudes over 120,000 ft and speeds of Mach 8 (5000 mph). Supposedly Fouche is a member of
Air Force Intelligence and a cryptological expert. He is now semi-retired from the DOD. I have done little fact checking regarding his claims (which
he presents in the book via "Science Faction). In any case, it's made an interesting story thus far.
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Closing comments:
The fact remains that technological superiority is completely and totally in the interest of our military. Whether that means the existence of the
SR-75 or that they are simply pumping money into computer simulations, wind tunnel tests, etc I cannot say. Here is an interesting link:
pdf.aiaa.org...