There are actually a number of ways a long tubular robot without
wheels can travel, all of which are utilized by snakes in
different situations. These vehicles are typically seen as
useful for pipe inspections and disaster recovery. A snake-form
is also a popular choice for experimenting with self-
reconfiguring robot swarms. Slithering locomotion actually
breaks down into at least three dominant modes: Friction
leverage sliding from large bends, as in a sidewinder, small
muscular pulses known as peristalsis (often several
simultaneously), as in worms, and lifting up the end of the
vehicle completely to advance, as in inchworms. - Snakes on a
Plane! That are Actually Laser-Wielding Robots - The Atlantic