Energy bars are the result of an almost a century-long quest for an emergency ration that was light, compact, and nutritious. They began as a nasty meltless chocolate bar, which became the D ration, produced by Hershey in the 1940s. They then took a detour through freeze-drying, being served in cubes during the 1960s space flights; astronauts claimed they cause nausea and weight loss. Finally, in the mid-1960s, the Natick Soldier Systems Center got inspired—by the Gaines-Burger dog food patty, the first intermediate-moisture food, which meant it stayed soft even when stored at room temperature for months. The first modern energy bar was one of these—although apricot, not hamburger, flavored—and was munched by David Scott on the Apollo 15 flight.