An unusual X-15….

Here is my 1/32nd-scale cardmodel build of Flight 2-19-35, flown by U.S. Navy test pilot Forrest Petersen in X-15-2, 66671, on 28 September 1961. The flight was intended to gather heat transfer and thermostructural data. It involved two types of temperature-sensitive paint — a gray paint on the left wing, tailplane, ventral stub and skid, and a green paint on the rear of the left side tunnel and right ventral speed brake, as well a rectangular patch on each side tunnel. There was an irregularly painted white patch on the right tailplane, and the lower bug eye camera housings appeared white as well. Petersen hit Mach 5.3 and an altitude of 101,800 feet.

The model is a conversion/repaint of the Ken West X-15A-2. I used 170gsm glossy stock, and the build involved shortening the fuselage and side tunnels, as well as numerous other modifications, scratchbuilt parts and improvements. While a friend digitally repainted some parts, I used Tamiya spray paints to replicate the gray and green thermal paints.

Both sides of 66671’s rudder showed heavy weathering even before the flight. The right side was particularly weathered; it carried the remnants of a stripe of gray thermal paint tested on an earlier flight. The stripe obscured the top portion of the serial number, and when technicians tried cleaning it off, it just made a bigger mess. The still-visible portions of the serial were scorched as well.

Weathering/scorching was done with markers of various colors.

In looking at photos from the flight, there is a curiosity on the left side of the tailcone. There are rows of different colored dots, painted somewhat haphazardly. Some appear scorched. Dennis Jenkins, co-author of "Hypersonic: The Story of the North American X-15," told me they were “tell alls,” dots of thermal paint that change color depending on how hot they get. He said they were cheaper than using thermocouples.