During Aug. and Sept.1973, Aug 1974, and July and Aug. 1975 Explorer was flown cooperatively with Colorado State University for Profs. Lew Grant and Bill Cotton. The objectives were to have students participate in and learn from research efforts and to investigate the microphysical characteristics of mountain cumuli forming over the high-altitude plains of South Park, Colorado. Additionally, a goal for NCAR/NHRE was to investigate the physical effects of seeding with AgI. Explorer was hangered and flew out of the Lake County Airport at 10,100 feet in Leadville, Colorado during these projects.  

During this time and in the 1960s and early 1970s Lew Grant was leading an operational and research winter cloud seeding program over the mountains of SW Colorado. Some individuals had associated the cloud seeding with heavy snowfall and the many avalanches occurring on the high altitude passes in that region and were opposed to the cloud seeding. Presumably because the NCAR/NOAA Explorer sailplane was a government facility that was doing some cloud seeding for research purposes near Leadville and in South Park, there was hostility towards this project by someone. On the night of Sept. 11, 1973 a fire was started with kerosene or gas in the corner of the Lake County Airport near the NCAR Sailplane. This fire badly damaged the left wing of the aircraft and deformed the plexiglass canopy. After the fire the left wing of N9929J was rebuilt in early 1974 by Beegle Aircraft in Greeley, Colorado and was ready for flights before the 1974 NHRE field project. Although the fire was investigated by the FBI, the perpetrator of the fire was never determined.