In space, no one wants any surprises. To avoid being caught off guard where no one can hear you scream, every step of every space mission is practiced on the ground (or underwater, or in the air). We take a look back at NASA's decades of creative methods of astronaut training. STS 135 Astronaut Rex Walheim practices spacewalking in the Neutral Buoyancy Laboratory near NASA's Johnson Space Center in 2010, in preparation for working on the exterior of the International Space Station. Walheim is the mission specialist for STS-135, the final flight of the space shuttle Atlantis (and the last shuttle flight ever), which took off on July 8. Below: Sandy Magnus, STS-135 mission specialist, gets fitted for her emergency spacesuit on March 29, 2011.

Wilderness Survival Training Wilderness survival training is an important part of NASA astronaut training, in case a spacecraft crashes far from civilization. Above: The seven original Mercury astronauts at Stead Air Force Base in Nevada, 1960. Some of their clothing is made from parachute material. From left to right: L. Gordon Cooper, M. Scott Carpenter, John Glenn, Alan Shepard, Virgil I. Grissom, Walter Schirra and Donald K. Slayton. Below: Astronauts participate in tropical survival training at Albrook Air Force Base near the Panama Canal in 1963. From left to right: an unidentified trainer, Neil Armstrong, John H. Glenn, Jr., L. Gordon Cooper and Pete Conrad.

Weightlessness Training Going underwater isn't the only way to simulate weightlessness. Flying an airplane in an arc gives astronauts in training a few seconds of floating. Above: Buzz Aldrin floats in an Air Force KC-135 jet in July 1969, just days before landing on the moon. Below: Gemini astronaut David R. Scott practices spacewalking in a C-135 Air Force plane in 1966.

Escaping Gemini Astronauts John Young (on top of the capsule) and Gus Grissom (in the water) practice escaping from a Gemini capsule in an indoor pool at Ellington Air Force Base, Texas, in this image from 1965. Gemini was NASA's second human spaceflight program, and included 10 manned flights in 1965 and 1966.

Apollo Moon Landing Astronauts Eugene Cernan (left), commander, and Astronaut Harrison Schmitt, scientist and lunar module pilot for the Apollo 17 mission, practice collecting samples in this Lunar Roving Vehicle in 1972.

Biosensors Astronaut Scott Carpenter, one of the original seven astronauts in the Mercury program, lies on a bed with biosensors attached to his head at Cape Canaveral in 1962. Carpenter was the pilot for Mercury-Atlas 7, the second orbital mission of NASA's manned space program. The spacecraft orbited the Earth three times, but an equipment malfunction forced Carpenter to control his return to solid ground manually. He landed 250 miles off course, but safe.

Remote Manipulator System Above: Crew of STS-61, the shuttle mission that first serviced the Hubble Space Telescope in 1993, practiced steering a dummy astronaut into position using the Remote Manipulator System. Below: Astronaut Ronald McNair, mission specialist for the STS 41-B mission, trains on the remote manipulator system (RMS) simulator in 1983.

Underwater EVA Training Being underwater is the next best thing to being in space. In the Johnson Space Center's weightless environment training facility (WETA), astronauts practice swimming through space to work outside of their vehicles. Above: Astronaut Robert L. Stewart trains for shuttle mission STS-41B in 1983. Below: STS-41B astronaut Bruce McCandless trains using a weighted version of the manned maneuvering unit. Divers assist shuttle crewmen Joseph P. Allen (foreground) and William B. Lenoir (at the top of the image) as they swim around a full-scale mockup of the shuttle's cargo bay in weighted space suits. Allen and Lenoir flew on STS-5 in 1982.

Centrifuge Mercury astronaut Walter M. Schirra Jr. entering a centrifuge used to test gravitational stress on astronauts preflight in 1960. Schirra piloted the Mercury-Atlas 8 space mission, which orbited the Earth six times in 1962.

Hubble Repair Training The Hubble Space Telescope originally launched in 1990 with a flawed mirror. The brilliant images the telescope is famous for were made possible by the crew of STS-61, a 1993 flight of the space shuttle Endeavour that brought Hubble corrective lenses. Astronauts practiced fitting Hubble with its new glasses in underwater training pools. Above: Astronaut Jeffrey A. Hoffman uses a power wrench to open a stowage facility in a pool at Marshall Space Flight Center. Below: Astronaut Kathryn C. Thornton practices repairing a full-scale model of Hubble's Wide Field/Planetary Camera in a pool at Johnson Space Center.

John Glenn in the Mercury Procedures Trainer John Glenn, one of the Mercury Seven astronauts, is shown here going through a training exercise in the Mercury Procedures Trainer. This spacecraft simulator was used to train astronauts in both normal and emergency modes.

Emergency Bailout Training Members of the crew of STS-67, a 1995 flight of the space shuttle Endeavour, float around Johnson Space Center's training pool as part of a mock emergency bailout. In the rafts, from left to right, are Scott D. Vangen, Ronald A. Parise and Samuel T. Durrance.

Ham Radio Training Astronaut Owen Garriot trains in 1983 with a Ham Radio he will operate during the STS-9 space shuttle mission.

Spacewalk Training NASA astronaut Mike Fossum practices spacewalking underwater in the Johnson Space Center's Neutral Buoyancy Laboratory. Fossum flew to the International Space Station on a Soyuz rocket in May, and is partway through a six-month tour of duty.

Parachute Training Above: Gemini astronaut Walter M. Schirra Jr. practiced parachuting out of a damaged spaceship and into Galveston Bay in 1965. __Below:__Schirra lands in the Bay. Russian cosmonaut Vladimir Titov, an alternate mission specialist for shuttle mission STS-60, simulates parachuting into water at Johnson Space Center's training pool in 1993.