It is not clear if the craft, which looks like a Zeppelin, is a hobby or something Brin hopes to turn into a business.
Brin is not saying anything about it - however he has been fascinated by airships from his visits to Ames which was home to the USS Macon, a huge airship built by the US Navy. In 1935 the Macon was damaged in a storm and lost off California's Big Sur coast.
Brin decided to build one of his own after seeing old photos of the Macon, because everyone wants to have a disaster of their own which was not just Google Wave.
Brin's airship is not an Alphabet project. Engineers have constructed a metal skeleton of the craft, and it fills up much of the enormous hangar. Alan Weston, the former director of programs at NASA Ames, is leading the airship project.
Zeppelins were rather cool technology which should have been developed and made safer. Unfortunately they are currently a little synonomous with flying fireballs.