Astronaut | EPFL Graph Search

An astronaut (from the Ancient Greek ἄστρον (astron), meaning 'star', and ναύτης (nautes), meaning 'sailor') is a person trained, equipped, and deployed by a human spaceflight program to serve as a commander or crew member aboard a spacecraft. Although generally reserved for professional space travelers, the term is sometimes applied to anyone who travels into space, including scientists, politicians, journalists, and tourists. "Astronaut" technically applies to all human space travelers regardless of nationality. However, astronauts fielded by Russia or the Soviet Union are typically known instead as cosmonauts (from the Russian "kosmos" (космос), meaning "space", also borrowed from Greek). Comparatively recent developments in crewed spaceflight made by China have led to the rise of the term taikonaut (from the Mandarin "tàikōng" (太空), meaning "space"), although its use is somewhat informal and its origin is unclear. In China, the People's Liberation Army Astronaut Corps astronauts

Head position during various locomotor executions after prolonged microgravity exposure

Grégoire Courtine

Head orientation in the sagittal plane was assessed before and the second and sixth days after a prolonged microgravity exposure (6 months) in 7 astronauts, which were instructed to execute various locomotor movements (stair ascent, jump down and level walk). Crewmembers systematically flexed down the head when they executed the locomotion the second day post-flight compared to the pre-flight walk. Cephalic orientation was normally positioned when movements was performed the sixth day after Earth re-entry. This head flexion may reflect a strategy used by cosmonauts to increase the vestibular sensibility, and then improve the control of the dynamic equilibrium during locomotor movements. The high rate of re-adaptation indicated that cosmonauts rapidly recovered their normal walking capacities despite the prolonged microgravity exposure

2002

Recovery of the locomotor function after prolonged microgravity exposure. I. Head-trunk movement and locomotor equilibrium during various tasks

Grégoire Courtine

Recovery of locomotor function was investigated in seven cosmonauts exposed to microgravity for 6 months. Crew members executed a locomotor task with visual cues (eyes open, EO) and without them (eyes closed, EC). The locomotor task consisted of ascending a two-step staircase, jumping down from a 30-cm high platform, and finally walking 4 m in the straight-ahead direction. Subjects were tested before the flight (D-30), and on the second day (R+2) and the sixth day (R+6) after the flight. Cosmonauts succeeded in all locomotor sub-tasks as early as R+2. In particular, microgravity exposure did not prevent cosmonauts from producing a straight walking trajectory even when blindfolded (deviation at R+2 with EO 2.0±0.7°, and with EC 4.7±1.9°). However, lateral movements of trunk were found to be increased at R+2 (16%), suggesting post-flight gait instability. Modifications of the timing of forward trunk movements were also detected at R+2. Unexpectedly, coordination patterns between head and trunk movements remained unchanged. The maximum amplitude of head pitches was 5° or less. Yet, the cosmonauts held their heads at lower positions at R+2 in comparison with their pre-flight postures, and they lowered their heads even further during blindfolded locomotion. In general, comparable spatial and temporal modifications of head and trunk movements at R+2 were observed during the stair and gait cycles. Mean values of locomotor descriptors measured at R+6 did not deviate from the pre-flight baseline. When performing jumps after the return from their flight, cosmonauts decreased the amplitude and speed of head rotation by approximately 50% in comparison with the pre-flight values. In addition, the timing of head pitches was uncertain after weightlessness. All the above changes endured at R+6. Previous studies reported that prolonged exposure to microgravity adversely affects the motor performance in the initial hours upon re-entry to Earth. However, gait analysis revealed that cosmonauts recovered near-optimal locomotor abilities as early as the second day post-flight. Results suggest a notable capability of the central nervous system to rapidly accommodate to changing physical environment and body properties. The role of head stabilization at a lower position is conjectured to be an adaptive response to microgravity-induced motor disorders

2004

Recovery of the locomotor function after prolonged microgravity exposure. I. Head-trunk movement and locomotor equilibrium during various tasks

Grégoire Courtine

2004