The Human Body in Space

FAA Safety Briefing
Cleared for Takeoff
4 min readMay 2

By Dr. Susan Northrup, FAA Federal Air Surgeon

Magazine cover.

On April 12, 1961, Yuri Gagarin became the first person to journey into space and orbit the Earth. Remarkably, this was less than 60 years after the first powered flight by the Wright Brothers on Dec. 17, 1903. Even more remarkably, it has been over 60 years since Gagarin’s space flight.

During that time, space flight has become almost routine. Space flight is no longer limited to a select few individuals rigorously screened, medically, and extensively trained for specific missions. Instead, the FAA requires the pilot or remote operator of a human spacecraft to have a FAA pilot certificate with an instrument rating (14 CFR part 460). After all, the spacecraft will transit through the national airspace system to get to space. In addition, each crew member with a safety-critical role must possess a FAA second-class medical certificate.

Space tourism began on April 30, 2001, when Dennis Tito spent eight days aboard the international space station. Over the past few years, the space tourism industry has expanded with multiple private companies providing transportation. Unlike the crew, there are no medical requirements for the passengers.

Photo of astronauts and cosmonauts conducting a medical emergency exercise on the International Space Station.
Photo of astronauts and cosmonauts conducting a medical emergency exercise on the International Space Station. (NASA photo)

Congress passed the 2004 Commercial Space Launch Amendments Act to safely open space to private commercial, scientific, and cultural enterprises. Any medical requirements are put in place by the operators themselves. However, Congress can always direct requirements at some future point; this was the case for the airline industry in which Congress mandated that the airlines accommodate passengers with medical conditions. As you probably suspect, ongoing discussions are already addressing the path ahead. Even though this is a work in progress, you might be interested in some of the medical issues of space flight.

Space is a harsh, unfriendly environment for humans. Aside from the obvious fact that there is essentially a vacuum outside the vehicle, humans face several medical concerns in space flight.

Space motion sickness affects up to 70% of astronauts and can last several days. This high frequency is seen in a group selected for good health and experienced in flight.

Calcium is mobilized from the bones in a microgravity environment and can lead to both kidney stones as well as weakening of the bones themselves. There is also muscle loss in a microgravity environment. Countermeasures for muscle and bone loss exist but only partially mitigate the effects of microgravity.

Radiation exists everywhere on the Earth, but it increases in low Earth orbit outside most of the atmosphere and increases again when outside the protection of the Earth’s magnetic fields.

The latter was a concern for the lunar missions and will be again for future missions to the moon and Mars. The acceleration forces on launch and re-entry are not insignificant and easily exceed 3 Gs, sustained for seconds or even minutes.

Post-flight effects include orthostatic intolerance (feeling faint) and neuro vestibular dysfunction (such as vertigo and instability). These issues affect everyone regardless of underlying health, but there is concern that those with compromised health might face more significant challenges. It is reassuring that centrifuge-based research studies have shown that most people do very well during simulated space flight profiles, even those with stable chronic diseases.

Many concerns are similar to those that impact passengers now, albeit more extremely: emergency egress for those with physical or mental limitations; exacerbations of underlying medical problems; medical emergencies without the ability to obtain treatment immediately (similar to transoceanic flights); loss of or decreased cabin pressure. My staff is looking at these issues, as are other governmental and industry organizations in the U.S. and worldwide. To help address these and other issues, FAA’s Office of Commercial Space Transportation hopes to publish updated guidance based on the 2014 initial release of “Recommended Practices for Human Space Flight Occupant Safety” by the end of this year.

Not that long ago, air travel was limited to the wealthy or adventurous. It might take longer for space travel to become as egalitarian as air travel, but we are preparing for it now.

Photo of Dr. Susan Northrup, FAA Federal Air Surgeon.
Dr. Susan Northrup, FAA Federal Air Surgeon
This article was originally published in the May/June 2023 issue of FAA Safety Briefing magazine.



FAA Safety Briefing
Cleared for Takeoff

Official FAA safety policy voice for general aviation. Part of the national FAA Safety Team (FAASTeam).