HUGE unkn aircraft passed/glided directly overtop our vehicle. moved slow /made NO sound until right overtop - unkn engine noise

We were traveling eastbound route 16. First spotted two huge headlights just above the tree line to our left (north). Only saw headlights until it was directly overhead, craft made NO sound at all on approach or after it passed us - only heard a light engine whine sound when directly overhead - We saw the underside of the craft it looked like a gigantic drone approximately the size of at least one big military tank. The craft was approximately 150 feet overhead - it seemed to clear the trees but was extremely low flying. Underside of the craft had grey / sliver markings that were in box like patterns - reminded me of the Star Wars space station markings. The craft appeared to gently glide past us heading into the corn field to our right (south). Thought it was going to land in the corn but lost sight of it as the corn was high. our travel speed was about 45mph and this craft we estimate to be traveling at no more than 30 to 40 mph. My husband is a private pilot, and he was shocked at the lack of prop wash or jet sounds to keep the craft airborne. Husband also noted one red light atop the vehicle, and he noted no typical aviation / navigation lighting. Husband was shocked how the size was able to stay airborne with such low speed.
My husband and I each drew what we saw (see illustrations below)