Tethers Unlimited, Inc. (TUI) is an American private aerospace company headquartered near Seattle, Washington, which performs research and development of new products and technologies for space, sea, and air. Founded in 1994 by Robert P. Hoyt and Robert L. Forward, Tethers Unlimited began developing products based on space tether technologies, including concepts for removal of space debris and momentum exchange tethers for launching payloads into higher orbits. TUI has since broadened its suite of technologies to include power, propulsion, actuation, and communications systems for small satellites, robotic technologies for on-orbit fabrication and assembly, optical fiber winding and deployment, software defined radio communications, and 3D printed radiation shielding.