S.G. Zaitsev in 1925 patented a “spherical tank”, which consisted of two nested spherical shells. The inner, non-rotating shell served as the main body of the vehicle, in its lower part all the mechanisms and the crew were located. The outer armor shell rotated, rolling the tank over the terrain. The movement of the machine took place with the help of an internal combustion engine due to the rotation of the outer shell relative to the stationary inner one. The directional control of the machine was carried out by moving a special load left-right, which caused a change in the center of gravity of the inner shell.