Japan's ministry of defense has developed a spherical flying machine that can hover like a helicopter, fly forward like an airplane and can even roll along the ground.
Conceptually, this machine is similar to circular-winged aircraft that were developed decades ago. Aerodynamicists have long known that circular wings can be extremely efficient. They are part of the class of design known as non-planar wings.
The aerodynamics of nonplanar wing systems that form closed loops are very interesting. Such configurations include box-planes, ring wings, joined wings, and "spiroid-tip" devices. Wings that form closed loops, such as the ring-wing illustrated below, do not eliminate the "tip vortices" or trailing vortex wakes even though the wing has no tips. Still, the vortex drag of the circular ring wing is just 50% that of a planar wing with the same span and total lift and the concept has been studied at several organizations, including early aviation pioneers, a major aircraft manufacturer, as well as several toy companies.