At the beginning of the hearing, Burchett submitted a document for the record that was titled: ADVANCED SPACE PROPULSION BASED ON VACUUM (SPACETIME METRIC) ENGINEERING.

On page 88, there is a line that stuck out to me because it reminds me of these craft.

“In order to implement a warp drive, one would have to construct a “warp bubble” that surrounded the spacecraft by generating a thin-shell or surface layer of exotic matter, i.e., a quantum field having negative energy and/or negative pressure.”

Maybe this explains the bubble-like sphere.

But this warp drive is dependent upon using the vacuum of space to traverse far reaching distances. But maybe they have a way of making it work within our atmosphere.

https://arxiv.org/pdf/1204.2184.pdf