Martin Marietta Model 845

Lore & Background

The Martin Marietta Model 845 was developed under the United States Air Force's Compass Dwell program, with two prototypes built. The airframes were based on a Schweizer SGS 1-34 sailplane and shared a similar configuration with the competing Ling-Temco-Vought XQM-93 design. Test flights began in April 1972; during testing, one prototype stayed aloft for almost 28 hours, but it failed to meet the Air Force's requirement of a 40,000 ft service ceiling. In 1973, the Model 845A was cancelled along with the XQM-93, the program being replaced by Compass Cope.

After cancellation, two 845 airframes were transferred by the Office of Naval Research to New Mexico Tech for use by the Langmuir Laboratory for Atmospheric Research, where they currently remain. Airframe 845A was converted into a piloted aircraft and used as a platform for atmospheric research, flying as SPTVAR (Special Purpose Test Vehicle for Atmospheric Research) until the late 1990s. Its missions included flights over the Langmuir Laboratory facility in south-central New Mexico, flying through thunderstorms and making measurements of the electric field inside clouds. The other airframe, still configured as the original drone design, is in storage at the same facility.

Reader's Guide

The Martin Marietta Model 845 is notable as a specialized communications relay drone developed for the Vietnam War, though it never entered operational service. Its design, based on a Schweizer sailplane, reflected an approach to endurance through glider-like aerodynamics. The program's cancellation in 1973, alongside the competing XQM-93, marked a shift toward the Compass Cope program. However, the airframes found a second life in atmospheric research, demonstrating the adaptability of the design. The conversion of one airframe into a piloted research vehicle (SPTVAR) allowed it to fly through thunderstorms and measure electric fields inside clouds, contributing to scientific understanding of storm physics. The other airframe remains in storage, preserving the original drone configuration. This dual legacy—as a canceled military project and a successful research platform—underscores the Model 845's unique place in aviation history.

Did You Know?

• The Model 845 was based on a Schweizer SGS 1-34 sailplane.
• After cancellation, airframes were transferred to New Mexico Tech for atmospheric research.
• The converted piloted version, SPTVAR, flew through thunderstorms to measure electric fields.