European Space Agency ground station engineer Mr Riise provided a markedly more simple idea.

He proposed sending power mechanically - effectively by providing a carefully timed jerk of the cable at its base.

To demonstrate, he employed a broomstick to represent the cable held in tension, and an electric sander to provide a rhythmic vibration to the bottom of the stick.

Around the broomstick's circumference he tied three brushes representing the climber with their bristles pointing downwards - meaning it took slightly more force to lower the brush assembly than to raise it.

The vibration from the sander allowed the assembly to slide upward along the broomstick as it moved slightly downward, but grip it as it moved slightly upward. The net effect: the assembly rose against gravity straight to the top of the stick.