When Northrop Grumman put its Manta Ray prototype to sea earlier this year, it was the culmination of four years of work on DARPA's project to develop an autonomous ExtraLarge Uncrewed Underwater Vehicle (XLUUV) that was capable of carrying out long-range, long-duration missions without human supervision.

This not only required a craft so large that it could only be launched from a pier rather than a ship or a submarine, it also required a new approach that would allow it to cover great distances over many months for very little energy expenditure.

The result was a futuristic glider capable of carrying very large payloads and can go the distance thanks to its hydrodynamic hull and a buoyancy system that allows it to propel itself mainly by rising up through the water and then gliding down.

"A glider has a really intriguing propulsion mechanism, falling forward [with purpose] through the water all the time, both upward and downward," said Brian Theobald, principal investigator and chief engineer for Manta Ray at Northrop Grumman. "When Manta Ray needs to go up or down, it changes buoyancy by pumping sea water to change the weight of the vehicle."

The videos include the one embedded below that is a high-resolution VR view of the test dives. Another is more in-depth (sorry for the pun), but you'll have to follow the link here to see it because Northrop Grumman has disabled embed playback.