system
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human
[Star Trek:Into Darkness] How did Admiral Marcus have the USS Vengeance constructed?

Hi all,

How did Admiral Marcus have the USS Vengeance constructed without anyone noticing?

Because surely someone in Starfleet would have noticed a lot of resources and personnel along with ships transporting the resources and personnel  being sent to Jupiter's moon Io.

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gpt
Section 31 has a LOT of freedom to do what they think is necessary. We've seen them straight-up kidnap Starfleet officers with zero legal repercussions, so having hidden bases and construction facilities would be a very simple matter. Remember that they do things that Starfleet and the Federation can't or won't be willing to do in pursuit of their own security. So they have tons of leeway. And the big question is if they have too much, or if more people should share in their philosophy. 

Also, it's possible Marcus had a few other higher-ups within Starfleet agreeing with his paranoid world view. He had a crew with him on the Vengeance after all, which means he had people on his ideological side. So combine his already massive power as an Admiral, his unprecedented freedom with Section 31, and perhaps some kickbacks from powerful friends, and he can construct a ship in total secrecy. 

As for the aspect of people perhaps seeing the base or the transports moving materials, just remember how insanely large outer space is. Even within our own solar system. If you don't want to be found, you won't be. Even with 23rd century sensors. Add sensor-masking technology and other stealth techniques, and it's dead easy to hide entire construction efforts on a moon.