Engage the (almost) silent drive - Aerospace America

https://aerospaceamerica.aiaa.org/features/engage-the-almost-silent-drive/ 

Navy Releases Timeline For Mysterious 2019 “UAS Swarm” Involving Warships Off California

https://www.thedrive.com/the-war-zone/44231/navy-releases-timeline-for-2019-uas-swarm-involving-warships-off-california