Aaron Weller began flying model airplanes more than 25 years ago, when he was 14. But the models of his youth didn't have the knife-sharp rotating blades, which spin at hundreds of times per minute, that he sees on today's drones. So when he began hearing about plans by companies such as Amazon to use unmanned aerial craft to deliver packages, he looked down at his young daughter and became concerned. If those drones malfunction and fall, their blades could hurt people. The Dataw resident has spent the last year and a half working on what he calls the "droplet." Because the propellers are inside the drone, they are not a danger to people nearby, Weller said. ...Continue reading via the source link below. Source: http://www.islandpacket.com/2015/04/11/3693834_beaufort-county-resident-creates.html?rh=1
It looks like the trick to protecting people and property from the blades is to make it into a balloon.