Here is a video on an interesting approach to powered flight, called the Ornicopter: Some of the more knowledgeable among you may know what an Ornithopter is - it's a machine that flaps its wings like a bird to achieve flight. An Ornicopter flaps its rotary wings/blades, causing them to travel in a rotary pattern like in a helicopter. Because the engine is not applying any torque, there is no counter-rotation problem, nor any tailboom-rotor required. A simpler piston-driven linear motor can be used, because it only needs to provide linear oscillation power to drive the flapping. This not only lowers the weight of the engine, but also improves engine reliability and ruggedness, reducing the likelihood of the engine seizing up or stalling. Like a gyroplane, the ornicopter would also be more stable in turbulence or cross-winds. But most importantly, the ornicopter is more efficient than a helicopter in higher-altitude thinner air, where it is easier to flap. This is because there is a non-linear relationship between the work required to do the flapping, and the lift generated from the resulting vortices. Why am I posting about it here? Well, I was thinking that the ornicopter might be useful for flying missions in the high Himalayas and Karakoram mountains, where India has its most militarized frontiers. If you see places like Siachen, these areas are particularly challenging for helicopters to fly in, because those conditions are at the limits of what the machines can perform. I think that DRDO should try to develop systems which are specific to the challenges of India's particular defense environment. The technology of the ornicopter is definitely worth looking into for further research and development.