Science Realm is a United States Government project with the aim of creating a vertical-takeoff horizontal-landing (VTOHL) single-stage-to-orbit (SSTO) craft, the term is also associated with the software this project uses to simulate takeoff and landing.
However, it became clear that horizontal takeoff requirement was an inappropriate application of rocket thrust-to-weight ratio; the angle and relative size of rocket and earth meant the path of least effort was almost completely vertical (completely against gravitation).
[2][3] The Space Maneuver Vehicle (SMV) completed a successful autonomous approach and landing on its first flight test on 11 August 1998.
The unmanned vehicle was dropped from a US Army UH-60 Black Hawk helicopter at an altitude of 9,000 feet, performed a controlled approach and landed on the runway.
This glide simulated the final approach and landing phases of such a vehicle returning from orbit.