Human spaceflight rests on the shoulders of kitties. Before shooting humans into space, NASA and the U.S. Air Force tested the low-gravity waters with smaller mammals, birds and insects. The propaganda videos of the time claimed the animal astronauts were ushering in "a new era -- not a Buck Rogers era in a science fiction world, but an age having its foundations in research." That may be true. But the resulting videos of these hapless creatures, which range from hilarious to disturbing, seem to best answer the question, "How does a creature that doesn't understand gravity respond to its absence?" Cat Can Has Gravity? Cats only land on their feet when they know which way is down. Researchers at the Air Force Aerospace Medical Research Laboratories in Dayton, Ohio sent cats flying in a C-131 jet on a trajectory that gave them 15 seconds of weightlessness. This footage is from an Air Force film called Bioastronautics Research. Video: U.S. Air Force Aerospace Medical Research Laboratories

Perplexed Pigeons The same team took pigeons aboard an airplane to see if they could fly in zero G. Pigeons normally stay horizontal while in flight, but lost feeling for what was up and down when the plane began to dive. Some even flew upside-down. Video: U.S. Air Force Aerospace Medical Research Laboratories

Microgravity Mice In experiments that were slightly more relevant to human spaceflight, researchers from the Wright-Patterson Air Force Base (now home to the Air Force School of Aerospace Medicine) sent mice and monkeys aloft in a rocket in 1953. The mice traveled in a sealed aluminum drum with two compartments, one of which had a shelf to cling to. The ball in the canister shows the direction of gravity. mouse with the shelf could orient himself in free fall; the other mouse completely freaked out. Both mice and monkeys were perfectly fine when they returned to Earth. "This brief test revealed no reason why man cannot fly 37 miles up in a rocket," the researchers concluded. Video: U.S. Air Force School of Aerospace Medicine

Confused Quails Even after human spaceflight was well established, space agencies kept shooting animals into space, to see how they would react. Here, quail chicks struggle to right themselves aboard the Russian MIR space station in the 1990s. Tragically, the birds' disorientation meant they couldn't eat. Researchers sacrificed the chicks two to four days after they hatched, rather than let them starve to death. Video: Russian Federal Space Agency

Baffled Butterflies Researchers from BioServe Space Technologies at the University of Colorado sent monarch butterfly larvae to the International Space Station in 2010 to see if they would hatch and metamorphose into butterflies in microgravity. They did, but the grown monarchs were utterly unable to fly. This painted lady bounces off the walls a few times before giving up. Video: BioServe Space Technologies at the University of Colorado – Boulder