Project SideArm is a system developed by DARPA, the US' military research organization. With the country's growing reliance on drones for conducting military operations, Project SideArm is a way to quickly get drones into and out of the air in potentially dangerous spaces, reducing the potential costs for the military as a whole.
Project SideArm is an adaptation of a system that has been used for decades on aircraft carriers. Anyone who's seen footage of a fighter jet landing on an aircraft carrier will recognize the system: the pilots guide their planes down toward the short runway, and a hook extending from the bottom of the plane catches a wire on the tarmac, thus slowing it to a stop. Project SideArm inverts that formula, with a hook on top of drones catching on to a sliding crane and causing the drone to jerk upwards, damage-free, into a net.