Related by context. Frequent words. (Click for all words.) 38 weightlessness 33 microgravity 33 jet lag 32 orbital outpost 32 cosmic radiation 32 Apollo astronauts 31 Russian cosmonauts 31 thrusters 31 cosmonaut 30 cosmonauts 30 zero gravity 30 spacecraft 29 jetlag 28 Padalka 28 International Space Station 28 crewmates 28 orbiting 28 spaceship 28 Malenchenko 27 astronauts 27 shuttle Atlantis 27 Shenzhou 27 curvature 27 orbital 27 Space Agency 27 weightless 27 Soyuz capsule 27 Space Station 27 polar orbit 27 Astronauts 26 outer space 26 orbiter 26 orbiting outpost 26 lunar orbit 26 Yurchikhin 26 spacesuit 26 orbit 26 Lopez Alegria 26 Soyuz 25 astronauts aboard 25 Russian Soyuz spacecraft 25 spacesuits 24 Thomas Reiter 24 orbiting laboratory 24 Martian surface 24 JAXA 24 rigors 24 spaceships 24 Vinogradov 24 hypersonic 24 blastoff 24 Earth orbit 24 flight simulator 23 spacewalkers 23 airlock 23 Soyuz TMA 23 Red Planet 23 Virgin Galactic 23 altitude 23 biological clocks 23 stage fright 23 turbulence 23 astronaut 23 lunar surface 22 Cape Canaveral Fla. 22 spacewalks 22 Orbiter 22 lunar landing 22 discomforts 22 Wakata 22 lander 22 shuttle Discovery 22 Dennis Tito 21 lunar lander 21 GlobalFlyer 21 layovers 21 yips 21 earthbound 21 lunar module 21 Gs 21 searing heat 21 space shuttle 21 motion sickness 21 Space Shuttle Atlantis 21 stiffness 21 shuttle astronauts 20 shuttle robotic arm 20 unfamiliar surroundings 20 circadian rhythms 20 relaxation techniques 20 ISS 20 Astronaut 20 boredom 20 scorching heat 20 centrifugal force 20 NASA 20 robotic arm 20 airship 20 liftoff 19 sleep deprivation 19 sub orbital