No one knows. It’s most likely in a need to know basis. That’s why it’s not public knowledge. If it was national security is easily compromised.
Same situation if you are defense contractor and you are selected to make a titanium whatever for an aircraft. You don’t know what plane it’s for, you don’t know what it does. You make the part. You get paid.
It’s difficult to wrap your mind around how things could and are going on that 98% of the government including the president doesn’t know about but it happens. The wackos that think Aera 51 is where they keep UFOs fail to realize its most likely no more than a secret test/fabrication site for aircraft just like vehicle manufacturers do with cars.