If Secret Space Program exist...

A ring/torus shape is the most logical.

Devices similiar to "free energy torus" machines.

Living space around the hole of the torus then. How many crew ?

The craft seen parked over the Arizona airforce base was "almost as big as the base", "cigar shaped", "looked allot like a blimp". But "as soon as it started to move is vanished".

I think the "hole" in the torus could be used for the "cockpit".

The crew.... well that depends. I have always thought any ships visiting earth would have to be "scout ships". Smaller than a "main ship". Probably a crew of 2 perhaps 3.

Made of material that is not of this world. Literally!

3.

Here are the orbital platforms...

Sorry here they are...

jeez wont embed

[link to youtu.be]

[link to discaircraft.greyfalcon.us]
[link to www.ufohowto.com]
[link to www.feandft.com]