In fact, rockets work more efficiently in the vacuum of space than in
an atmosphere. Multistage rockets are capable of attaining escape
velocity from Earth and therefore can achieve unlimited maximum
altitude. Compared with airbreathing engines, rockets are lightweight
and powerful and capable of generating large accelerations. To control
their flight, rockets rely on momentum, airfoils, auxiliary reaction
engines, gimballed thrust, momentum wheels, deflection of the exhaust
stream, propellant flow, spin, or gravity.
"Astronaut" technically applies to all human space travelers
regardless of nationality or allegiance; 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) in order to distinguish them from American or
otherwise NATO-oriented space travellers. Comparatively recent
developments in manned 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 Mainland China, the People's Liberation Army Astronaut
Corps astronauts and their foreign counterparts are all officially
called hángtiānyuán (航天员, meaning "heaven navigator" or literally
"heaven-sailing staff").
Astronaut
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
terms are sometimes applied to anyone who travels into space,
including scientists, politicians, journalists and tourists.
Definition
As of 17 November 2016, 552 people from 36 countries have reached
100 km (62 mi) or more in altitude, of whom 549 reached low Earth
orbit or beyond. Of these, 24 people have traveled beyond low Earth
orbit, either to lunar orbit, the lunar surface, or, in one case, a
loop around the Moon. Three of the 24—Jim Lovell, John Young and
Eugene Cernan—did so twice.
Parastronaut
For its 2022 Astronaut Group, ESA envisions recruiting an astronaut
with a physical disability, a category they called "parastronauts",
with the intention but not guarantee of spaceflight. The categories
of disability considered for the program were individuals with lower
limb deficiency (either through amputation or congenital), leg
length difference, or a short stature (less than 130 centimetres or
4 feet 3 inches)