Experiments make up most of the 6,400 pounds of cargo, The Associated Press reported. That includes 20 mice. The Dragon capsule is also doubling as an ice-cream truck this time. There was extra freezer space, so NASA packed little cups of vanilla, chocolate and birthday-cake ice cream for the station's crew of six, as well as ice cream candy bars. Those treats should be especially welcomed by U.S. astronaut Peggy Whitson, in orbit since November.