Q&A: Becoming an astronaut—challenges and preparation for the final frontier

The return of astronauts Butch Wilmore and Sunita Williams last month has reignited conversations about the physical and psychological conditioning astronauts undergo when traveling to and returning from space.

Laura Kelley, a media relations specialist in the Office of Communications, sat down with Arian Anderson, MD, assistant professor in the Department of Emergency Medicine at the University of Colorado School of Medicine and expert on health and performance in extreme environments and human spaceflight, to discuss the hurdles of space travel and how CU Anschutz and CU Boulder are joining forces to train the next wave of innovators supporting astronauts on missions to the moon and Mars.

How hard is it to become an astronaut?

Extremely. Becoming an astronaut is no easy feat. In 2020, there were 12,000 applicants for just 10 positions, yielding a less than 0.01% acceptance rate. Selected candidates typically come from backgrounds like the military, research or clinical fields, but they all share something essential: the ability to stay calm under pressure. Whether it's during a fire or a depressurization event, astronauts need the mental fortitude to perform complex procedures in life-threatening situations.

How do they prepare for the job once selected?

It starts with years of rigorous training as NASA astronaut candidates, or ASCANS. This preparation includes mastering all aspects of spaceflight: launching, docking with the International Space Station, conducting repairs and providing medical care. Astronauts are trained for normal operations as well as emergencies. As they approach their specific mission, their training intensifies, including specialized instruction on spacecraft (such as the Dragon Capsule or Russian Soyuz), spacewalks and the scientific experiments they will conduct.

They also receive guidance from dedicated teams managing their diet, exercise, sleep and mental health—like professional athletes preparing for a high-stakes performance.

How does space affect the body?

Living in space comes with significant physical challenges that affect almost every system. For example, without gravity, astronauts experience a loss of muscle and bone density. This isn't problematic in space, but it becomes an issue upon return to Earth, where astronauts often need help walking and risk broken bones. Additionally, the effects of gravity, radiation and confinement suppress the immune system and make them prone to infection, negatively affect their sleep cycles, cause blurring of their vision and much more.

A large proportion of an astronaut's time is spent on health maintenance like exercise and targeted nutrition to minimize the effects. These physical hurdles are particularly concerning as plans for Mars missions unfold, where these effects will be magnified and support limited.

With that in mind, how would you plan long space flights, like going to Mars?

A mission to Mars presents a unique set of challenges. The crew will spend about nine months in transit, and once on the Martian surface, they must perform critical tasks within hours of landing. This necessitates a deeper understanding of astronaut health in space and on other planets.

At the University of Colorado, a team from the School of Medicine and Smead School of Aerospace Engineering Sciences is collaborating to address these health challenges, with the aim of developing countermeasures or solutions that integrate our expertise in medicine and engineering.

Aside from physical challenges, what mental hurdles does space travel pose?

Mental health is a major concern. Extended isolation in the confined quarters of a spacecraft can have profound effects on astronauts' psychological well-being. While Earth-based communication can help alleviate feelings of isolation during missions orbiting Earth, future missions—like those to Mars—will face delays in communication due to vast distances. As a result, astronauts will only be able to send brief messages instead of engaging in real-time conversations.

Extensive psychological tests and resiliency training are part of astronaut selection and mission preparation, but even the most mentally prepared individuals may struggle with the social and psychological strains of a Mars mission, which will take years from start to finish.

How long does it take to recover from time in space?

Astronauts readapt to living on Earth relatively quickly, but it takes time to get them back to their baseline. In the first 24–48 hours, they struggle because they are deconditioned, dehydrated and nauseated. Some feel better quickly, but others spend a few days feeling weak and sick.

After this initial period, they spend weeks undergoing exercise and strength training, as well as debriefing. Some effects, like bone density loss or an increased risk of cancer, may persist throughout their lives, but ongoing research aims to better understand these long-term impacts. After the first few weeks they are back to where they were before the mission.

How long is astronaut health monitored once they return to Earth?

NASA continuously monitors astronauts' health through the Lifetime Surveillance of Astronaut Health (LSAH) program. This provides lifelong health care to astronauts and offers valuable data for understanding the long-term effects of spaceflight. With space travel becoming more accessible, it's crucial to understand and mitigate the health risks associated with living and working in space.

Given the impacts on the body and mind, what does it mean for future of space travel?

The challenges of spaceflight are daunting but not insurmountable. Space missions have evolved from proving human survival in space to exploring new frontiers on the moon and Mars. We are returning to an era similar to the Apollo missions, where astronauts are adventurers and explorers rather than scientists.

At CU, we are working to meet the health needs of astronauts who may eventually be living on other planets through our Masters in Aerospace Engineering Sciences Program, ensuring the next generation of explorers is prepared for these challenges.

Provided by CU Anschutz Medical Campus