Martin Marietta Model 845

The Martin Marietta Model 845 was a drone built for the United States during the late 1960s and early 1970s, intended to serve as a communications relay in the Vietnam War. Two prototypes were constructed under the Air Force’s Compass Dwell program. They were derived from a Schweizer SGS 1-34 sailplane and shared a similar layout with the competing Ling-Temco-Vought XQM-93.

Flight testing started in April 1972; one prototype stayed airborne for nearly 28 hours, but it could not reach the required service ceiling of 40,000 feet. The Model 845A was canceled in 1973, along with the XQM-93, and the program was replaced by Compass Cope. After cancellation, the Office of Naval Research transferred two airframes to New Mexico Tech for use by the Langmuir Laboratory for Atmospheric Research, where they remain.

One airframe, the 845A, was converted into a manned aircraft and used for atmospheric research as the SPTVAR (Special Purpose Test Vehicle for Atmospheric Research) until the late 1990s. It flew over the Langmuir Laboratory in south-central New Mexico, passing through thunderstorms to measure electric fields inside clouds. The other airframe, still in its original drone configuration, is stored at the same facility.