How to Prepare for Human Spaceflight

Preparing for human spaceflight means checking a candidate’s health, completing a training program, and learning how to act in weightlessness and possible emergency situations.

Spaceflight demands more than physical endurance: psychological readiness, teamwork and knowledge of onboard procedures all matter. Let’s look at what preparation involves and why each stage is important for crew safety.

How does selection for human spaceflight work?

Selection for human spaceflight takes place in several stages: candidates are assessed on their ability to remain effective under heavy workloads. The first human spaceflight lasted 108 minutes, but mission preparation involves assessing not only physical health but also psychological readiness.

Stress resilience matters because cosmonauts must keep carrying out tasks even when pressure makes it hard to concentrate. In the crew’s confined environment, psychological readiness helps them stay focused and work with their crewmates; good health alone is not enough.

Selection and training are different stages

Selection determines whether a candidate is suited to further training, but it does not prepare them for flight by itself. After selection, cosmonauts must develop professional skills and learn how to act in mission conditions: passing selection is the start of the journey, not a substitute for training.

What does crew training involve, and how is readiness assessed?

Cosmonaut training combines exams with practical exercises: around 150 exams assess readiness to handle a wide range of tasks, while exercises teach candidates to apply their knowledge at the right moment. It is not enough to remember the procedures; they must be able to carry them out in conditions unlike those on Earth.

Practice on Earth and adaptation in space

Ground training lets cosmonauts practise actions in advance for working in the space environment, where familiar conditions on Earth do not apply. But training cannot replace adapting to weightlessness: people perceive and experience things differently there, so getting used to it remains part of flight preparation.

The United Nations Office for Outer Space Affairs maintains the Register of Objects Launched into Outer Space on behalf of the Secretary-General. The register tracks objects launched into space; cosmonaut exams and training, in turn, are intended to assess and develop the crew’s readiness for work.

How does weightlessness affect the body at the start of a flight?

At the start of a spaceflight, weightlessness changes how the body’s position and movement are perceived: familiar signals from life on Earth no longer match what a person experiences in the new environment. Changes in how the vestibular system works can cause space motion sickness—an unpleasant reaction to unfamiliar sensations during movement.

How adaptation happens

Cosmonaut training includes exercises for the vestibular system to familiarise it in advance with conditions unlike those on Earth. This preparation can help people cope with the changes, but it does not eliminate the need to adapt: the body gets used to weightlessness gradually, and unfamiliar sensations may persist even after ground training.

How a person feels during a flight does not stay the same throughout. As they get used to the new environment, their perception of their body and movement changes; that is why flight readiness involves not only training but also time to adapt.

How do everyday constraints change work in orbit?

Everyday constraints change work in orbit because cosmonauts have to perform familiar tasks without the usual support of a floor or the familiar sensation of weight. In weightlessness, the positions of people and objects can change, so movement must be controlled differently than on Earth. Even a simple task requires attention to how to steady the body and handle objects.

Cosmonaut training teaches people to carry out actions in sequence in an unfamiliar environment: to take their body position into account, keep track of objects and avoid relying on sensations they have on Earth. This matters both for everyday activities and for crew tasks—a disruption to the usual sequence of movements can make either more difficult.

Why adaptation matters

The vestibular system has to adapt to weightlessness, helping cosmonauts cope with space motion sickness. Ground training prepares them to act, but it does not make orbit a familiar workplace. Its purpose is to help the crew maintain a sequence of actions when sensations and conditions differ from those on Earth.

Which limits of training cannot be overcome in advance?

Ground training cannot fully overcome the challenges posed by weightlessness: even practised exercises cannot recreate exactly how a person will perceive movement and orient themselves in orbit. The vestibular system needs time to get used to the new conditions, so it is a mistake to expect all unfamiliar sensations to disappear before launch.

Stress resilience helps cosmonauts stay composed, but it does not replace checks of their knowledge and practical skills. Before a flight, candidates undergo a multistage selection process, and their training includes around 150 exams: readiness to handle pressure does not mean that specific skills can go untested.

Selection and training reduce risks, but they do not make spaceflight simple. The crew still has to adapt in orbit, where weightlessness changes familiar perceptions and tolerance of movement; this part of preparation continues in the real conditions of flight.

What happens after returning to Earth?

After returning to Earth, cosmonauts need time for their bodies to readjust to familiar sensations and conditions after weightlessness. Life does not return to normal instantly: after an orbital flight, the familiar signals the body relies on on Earth are perceived differently.

Two stages of adaptation

Getting used to orbit and recovering after returning are two different stages of the same process: the body moves between unfamiliar conditions. Before a flight, vestibular training helps cosmonauts cope with space motion sickness, but ground training cannot make weightlessness feel entirely familiar; after landing, the readjustment in the opposite direction begins.

Training is valuable because it teaches the crew to act not only during flight but also when moving between environments. Cosmonauts have to handle many tasks and remain ready as familiar sensations change; returning is therefore not a formality but a separate period of adaptation that takes time.

Which institutions are involved in spaceflight?

The United Nations Office for Outer Space Affairs and the United Nations Committee on the Peaceful Uses of Outer Space are involved in spaceflight preparation and international regulation. The Office is part of the United Nations Office at Vienna and serves as the Committee’s secretariat.

The United Nations Committee on the Peaceful Uses of Outer Space considers issues related to the peaceful uses of outer space through two subcommittees: the Scientific and Technical Subcommittee and the Legal Subcommittee. This structure brings together discussions of technical issues in space activities and consideration of their legal aspects.

International registration of space objects

The United Nations Office for Outer Space Affairs maintains the Register of Objects Launched into Outer Space on behalf of the UN Secretary-General. The register provides for the international registration of space objects; this function complements the Office’s work as the Committee’s secretariat.

Frequently asked questions

Key takeaways

• Selection assesses candidates’ stress resilience and readiness to work in challenging conditions.
• Flight preparation includes around 150 exams.
• The vestibular system is trained to help with adaptation to weightlessness and space motion sickness.
• Getting used to orbit and readjusting after returning both take time.
• The first human spaceflight lasted 108 minutes.