Medicine in the Final Frontier

Why do we explore? The answer is the same for those who push the limits of human experience on the Earth and those who leave the bounds of Earth for space. We long to know what is over the next hill, to test the limits of our endurance and capability, to experience nature, the Earth, and the planets of the Solar System—rare and beautiful—ourselves. To experience these things and not to just read about them or watch them on a screen is fundamental to our humanity and our sense of place in the universe. And where humans explore, humans get injured, or sick, or just want to maintain their health and performance so that they can keep exploring. This motivation led to the development of wilderness medicine as a discipline. This same motivation also drives space medicine.

Space remains the final frontier of exploration. Space beyond low Earth orbit is a distant wilderness characterized by limited resources; confined spaces; exposure to extended periods in microgravity, cosmic radiation, and isolation; and in some cases the impossibility of rescue or early return to the Earth. For almost 70 years, human spaceflight was limited to those with “the right stuff.” ¹ Only governments could afford the cost of getting to space, and governments selected the healthiest astronauts and cosmonauts they could find to minimize medical and operational risk. In November 2020, however, the calculus of human spaceflight changed when a private company delivered astronauts to the International Space Station. ² Today, access to space is expanding rapidly; companies are offering tourists short hops into suborbital space, creating opportunities for a wide range of people to leave the Earth. One company expanded the age range of those who have experienced spaceflight from 18 to 90 y.^3,4 Recently, an astronaut with a below-knee amputation was qualified for flight to the space station by the European Space Agency. ⁵ In short, new opportunities to explore space are allowing a broader set of people to leave the Earth.

Today, 3 things are changing because of the commercialization of spaceflight. As discussed earlier, the people who fly are changing. The business models, which in large part depend on space tourism at this point, require that those companies enable as many people to fly as possible. ⁶ They no longer have the luxury of selecting out human risk if they want to remain viable. Second, the vehicles, habitats, and space suits that protect people in space are changing. Most of the commercial spaceflight industry is in early phases of iterative design for vehicles and habitats that require input from physicians and other health professionals about how systems should be designed to accommodate the new medical risks and emerging acute-care needs that have not been faced before in spaceflight. ⁶ And third, the missions are changing. We are asking astronauts to do different jobs than we had done in the past. Future astronauts may be involved in construction on the Moon for a lunar base, operating in lunar orbit, supporting space tourism, and eventually manufacturing or research work in low Earth orbit. Together these changes are driving both innovation and risk in human spaceflight over the next decades.^7–10

Recognizing the similarities between the extreme environments in space and on Earth, the National Aeronautics and Space Administration (NASA) has used the Earth's wilderness spaces to train astronauts for spaceflight. This includes the National Outdoor Leadership School, Antarctica, the NASA Extreme Environment Mission Operations Project, and other locations.^11–14 These analogues are used for various purposes—training and simulation, evaluation and advancement of technology and procedures, scientific research regarding the human response to isolation and confinement, and more. Just as terrestrial wilderness environments provide an analogue for space, space medicine has an analogue in wilderness medicine.

Space is a resource-limited setting. Much like wilderness medicine, space medicine operates in an austere environment with an array of diverse challenges to human health. As for explorers in any remote area, logistics and resupply are a challenge. Developing and qualifying hardware for use in space require insight into the unique physical and operational environment. ¹⁵ Instead of unpredictable weather, astronauts experience dynamic loads and unique vibration environments during launches and landings. But space also has some completely novel challenges: Long stays in microgravity can decondition muscles, weaken bones, change circulation, and even affect the immune system. Cosmic radiation leads to cellular damage of uncertain consequence.^16,17 Isolation and confinement create mental health challenges. ¹⁸ As we go farther from Earth, the ability to supply the things needed by both astronauts and the vehicles they rely on for survival become more precarious. ¹⁹ But the explorers who climb mountains or explore underwater trenches have more in common with space explorers than they have differences. And the medical expertise required to protect space explorers’ health and performance draws heavily on the broad and deep experience of the wilderness medicine community.

This special issue of Wilderness & Environmental Medicine highlights the work being done to share knowledge between space medicine and its terrestrial counterparts. Space medicine as a discipline is growing rapidly: In the last 3 y alone, 5 new training programs have emerged at various universities in the United States that focus on space or aerospace medicine for civilians. This doubles the existing number of programs from just 3 y ago that were available to trainees through the aerospace medicine pathways already in existence. And 3 of those programs were military only, focused on aviation rather than space. The changes that are occurring now in this industry will shape both space and terrestrial medicine for decades to come. These changes create increased opportunities to share knowledge and skills among the physicians and researchers who study and treat humans in extreme environments. We are pleased to share this special issue with you.