The small UAV in the photo above that looks like a flying saucer is the Embler demonstrator from the AESIR UAS company. UK-based AESIR originates from the GFS Projects, a small start-up from Geoff Hatton (GFS stands for Geoff's Flying Saucers). Its core product is air vehicles that take advantage of the Coanda Effect in order to produce a stable and practical VTOL UAV that can hover and navigate even inside buildings.---



AESIR have already made several prototypes that have demonstrated their capability for stable and controllable flight. The basic concept has many advantages over conventional ducted fan drones like the RQ-16 T-Hawk from Honeywell (photos below)



The AESIR concept instead of a ducted fan, places a fan on top of a dome that by exploiting the Coanda effect channels the downstream air to a cone thus lifting a vehicle. In short the Coanda effect describes the tendency of a liquid to follow the curvature of an adjacent object and change the direction of the stream. As mentioned above such a UAV is inherently stable because it is floating over a cone of air instead of a column like a regular ducted fan. It has also some major packaging advantages as you can see in the sketch below:



With orange there is the payload, with black the power-plant and with blue the flaps that direct the downstream from the dome (AESIR) or directly below the fan (Honeywell).

The AESIR design not only allow a more compact vehicle for the same equipment (or more usable volume for the same fan size) but it has much better weight distribution by placing all the heavy parts inside and at the lower part of the vehicle. Surveillance packages that down-looking placement will also have a favorable placement.



Prototypes have been used in conjunction with UGVs and while the technology is scalable more multi-fan vehicles could follow, like the twin fan oval shaped UAV above.

For more info visit the AESIR website: http://www.aesir-uas.com
You can see a video of a flight here: http://www.aesir-uas.com/video.htm
Additional info on ARES blog: http://www.aviationweek.com/aw/blogs/defense

video with the Coanda effect AESIR UAV flying:

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(AESIR images by AESIR-UAS, RQ-16 images by Honeywell/US Navy, sketch from robotpig.net)