Dave Lang did his first tethered system analysis in 1961, studying the possibility of using multiple tethers to spin up and stabilize two objects in space to provide artificial gravity for Astronauts. He presented this work to WADC at Wright Field and an Advanced Concepts group at NACA Langley.

Within 4 years he was analyzing a demonstration of artificial gravity by spinning a Gemini Space capsule tethered to an Agena rocket in orbit; this was demonstrated on the Gemini XI Mission. Next he analyzed the possibility of gravity gradient stabilization of two spacecraft in orbit using a tether; this was experimentally verified on the Gemini XII Mission. He trained the Astronauts in tether operations, then participated as a tether specialist in NASA's Mission Control Center during both tethered Gemini Missions.

In 1967, the early forerunner of his (later) GTOSS code was employed by NASA to analyze parachute shroud dynamics for the Apollo launch escape and landing system.