Human spaceflight

These nations developed intercontinental ballistic missiles for the delivery of nuclear weapons, producing rockets large enough to be adapted to carry the first artificial satellites into low Earth orbit.

The US also made two North American X-15 flights (90 and 91, piloted by Joseph A. Walker), that exceeded the Kármán line, the 100 kilometres (62 mi) altitude used by the Fédération Aéronautique Internationale (FAI) to denote the edge of space.

In 1961, US President John F. Kennedy raised the stakes of the Space Race by setting the goal of landing a man on the Moon and returning him safely to Earth by the end of the 1960s.

The crew of Apollo 13—Jim Lovell, Jack Swigert, and Fred Haise—survived an in-flight spacecraft failure, they flew by the Moon without landing, and returned safely to Earth.

In 1969, Nixon appointed his vice president, Spiro Agnew, to head a Space Task Group to recommend follow-on human spaceflight programs after Apollo.

However, Nixon knew the American political climate would not support congressional funding for such an ambition, and killed proposals for all but the Shuttle, possibly to be followed by the space station.

During that time, President Richard Nixon and Soviet general secretary Leonid Brezhnev were negotiating an easing of Cold War tensions known as détente.

The first uncrewed spacecraft, Shenzhou 1, was launched on 20 November 1999 and recovered the next day, marking the first step of the realization of China's human spaceflight capability.

[16] It was later visited by multiple cargo and crewed spacecraft and demonstrated China's capability of sustaining Chinese astronauts' long-term stay in space.

A string of failures in 1998 led to funding reductions, and the project's cancellation in 2003 in favor of participation in the International Space Station program through the Kibō Japanese Experiment Module and H-II Transfer Vehicle cargo spacecraft.

As an alternative to HOPE-X, NASDA in 2001 proposed the Fuji crew capsule for independent or ISS flights, but the project did not proceed to the contracting stage.

Under the Commercial Crew Development plan, NASA relies on transportation services provided by the private sector to reach low Earth orbit, such as SpaceX Dragon 2, the Boeing Starliner or Sierra Nevada Corporation's Dream Chaser.

[26][27] SpaceX, Boeing, Blue Origin, and Virgin Galactic plan to fly commercial passengers in the emerging space tourism market.

Somewhat analogous to travel by airliner after the middle of the 20th century, these vehicles are proposed to transport large numbers of passengers to destinations in space, or on Earth via suborbital spaceflights.

These endeavors have also formerly been referred to as "manned space missions", though this is no longer official parlance according to NASA style guides, which call for gender-neutral language.

[55] Since 2008, the Japan Aerospace Exploration Agency has developed the H-II Transfer Vehicle cargo-spacecraft-based crewed spacecraft and Kibō Japanese Experiment Module–based small space laboratory.

The first step has begun with Artemis I in 2022, sending an uncrewed Orion spacecraft to a distant retrograde orbit around the Moon and returning it to Earth after a 25-day mission.

SpaceX is developing Starship, a fully reusable two-stage system, with near-Earth and cislunar applications and an ultimate goal of landing on Mars.

Several other countries and space agencies have announced and begun human spaceflight programs using natively developed equipment and technology, including Japan (JAXA), Iran (ISA), and North Korea (NADA).

[69][70] On 2 November 2017, scientists reported, based on MRI studies, that significant changes in the position and structure of the brain have been found in astronauts who have taken trips in space.

[76] Medical data from astronauts in low Earth orbits for long periods, dating back to the 1970s, show several adverse effects of a microgravity environment: loss of bone density, decreased muscle strength and endurance, postural instability, and reductions in aerobic capacity.

[91] This solar storm, which occurred in August 1972, could potentially have caused any astronauts who were exposed to it to suffer from acute radiation sickness, and may even have been lethal for those engaged in extravehicular activity or on the lunar surface.

Depression, anxiety, cabin fever, and other psychological problems may occur more than for an average person and could impact the crew's safety and mission success.

Un-tethered spacewalks were performed on three missions in 1984 using the Manned Maneuvering Unit, and on a flight test in 1994 of the Simplified Aid For EVA Rescue (SAFER) device.

A wing-leading-edge reinforced carbon-carbon heat shield had been damaged by a piece of frozen external tank foam insulation that had broken off and struck the wing during launch.

The use of a gas mixture carries the risk of decompression sickness (commonly known as "the bends") when transitioning to or from the pure oxygen space suit environment.

An electrical fire started in the cabin of Apollo 1 during a ground test at Cape Kennedy Air Force Station Launch Complex 34 on 27 January 1967, and spread rapidly.

The March 1966 Gemini 8 mission was aborted in orbit when an attitude control system thruster stuck in the on position, sending the craft into a dangerous spin that threatened the lives of Neil Armstrong and David Scott.

The third lunar landing expedition, Apollo 13, in April 1970, was aborted and the lives of the crew—James Lovell, Jack Swigert, and Fred Haise—were threatened after the failure of a cryogenic liquid oxygen tank en route to the Moon.

The tank failure was determined to be caused by two mistakes: the tank's drain fitting had been damaged when it was dropped during factory testing, necessitating the use of its internal heaters to boil out the oxygen after a pre-launch test; which in turn damaged the fan wiring's electrical insulation because the thermostats on the heaters did not meet the required voltage rating due to a vendor miscommunication.