Stepping disk

Stepping Disks are a fictional teleportation technology from the Known Space universe created by Larry Niven. They were invented by the Pierson's Puppeteers, and their existence is not generally known to other races until the events of "The Ringworld Engineers".

The stepping disks are an outgrowth and improvement of the transfer booth technology used by humans and other Known Space races. Unlike the booths, the disks do not require an enclosed chamber, and somehow can differentiate between solid masses and air, for example. They also have a far greater range than transfer booths, extending several AU's (equivalent to Earth's orbit).

Several limitations to stepping disks are mentioned in the Ringworld novels. If there is a difference in velocity between two disks, any matter transferred between them must be accelerated by the disk accordingly. If there is not enough energy to do so, the transfer cannot take place. This becomes a problem with disks that are a significant distance apart on the Ringworld surface, as they will have different velocities: same speed, different direction.