Hopi-Dart was a two-stage vehicle, combining a solid-fuelledHopi III first stage with an unpowered Dart second stage. It was originally capable of carrying a payload of to an apogee of ; an upgrade, sometimes known as "Hopi Plus", increased the apogee to. The Hopi-Dart was developed for NASA Marshall Space Fight Center to obtain wind speeds at altitudes from 70 to 90 kilometers in support of Saturn launches. Design was headed by Charles W. Watson.