As a followup to THIS (based on the photos HERE) a link was posted to this paper:

Navy Shipboard Lasers for Surface, Air, and Missile Defense: Background and Issues for Congress

It contains some illustrations that, while not being exactly what’s on the back of the ship, look pretty close:

This is the LaWS (Laser Weapon System), a solid-state laser which uses six commercial welding lasers to produce a 33 kilowatt laser beam. The laser is about 25% efficient meaning a projected operational version with a 100 kW beam would require 400 kW of total electrical power (and a whole lot of cooling). Compare the above image to this:

And this rear view of the LaWS from the PR video below:

Additionally, the LaWS prototype and the Thing On The Boat both have the same NAVSEA logo on ’em:

[youtube vqLkpcHavZE]

A view of the LaWS prototype from the PR video with a human in frame, compared to the Thing On The Boat photo (with a human moved a bit) shows that the devices are roughly the same size.

Further: The boxlike thing on the mount, further aft:

This bears some resemblance to the beam director of the Navy/Northrop Grumman Maritime Laser Demonstrator:

The MLD has already been tested at sea. So what we *may* have here is a comparison test between two laser systems; this would explain the two laser directors and the two Caterpillar power generators. Both lasers could presumably be fired up at once on their own power systems and tested simultaneously, providing direct comparisons of performance under various conditions. Alternatively, they may be used for different targets. As the video below shows, the MLD has apparently been used to take out small surface vessels. So… the LaWS aims up, the MLD aims down.

[youtube awsQs4ct0c4]