Gemini 4 was the second of 10 manned Gemini missions. On June 3, 1965, Ed White became the first American to perform an extravehicular activity (EVA) or "spacewalk." During his 20 minutes outside Gemini 4, White remained connected to the spacecraft by the golden "umbilical cord," and he used a hand-held jet thruster to maneuver in space. His crewmate, Jim McDivitt remained inside the vehicle.

The Gemini heatshield was a dish-shaped structure that formed the large end of the reentry module. Constructed of a load-carrying Fiberglas sandwich structure consisting of two 5-ply faceplates of resin-impregnated glass cloth separated by a 0.65inch thick Fiberglas honeycomb core, an additional Fiberglas honeycomb was bonded to the convex side of the sandwich and filled with Dow-Corning DC-325 ablative material.

The attached segment of Gemini 4 heatshield was exposed to the intense frictional heat of reentry into the atmosphere.