How does space change the human body? - What in the World podcast, BBC World Service

Key Concepts

• Zero gravity effects on the body: bone density loss, muscle mass loss, fluid redistribution.
• Radiation exposure in space: genetic changes, increased cancer risk.
• Space adaptation sickness: inner ear fluid disruption, balance issues.
• Countermeasures for space travel effects: exercise, shielding, specialized equipment.
• Spacesuits: protection from vacuum, temperature extremes, radiation, micrometeorites.

Effects of Space Travel on the Human Body

Gravity and its Absence

• On Earth, gravity constantly pulls us down, requiring our bodies to work to stay upright.
• In space, the absence of gravity leads to significant physiological changes.
• Astronauts Butch Wilmore and Suni Williams experienced these effects firsthand during their extended stay on the International Space Station (ISS).

Bone and Muscle Loss

• Without gravity, bones and muscles don't have to work as hard, leading to a decrease in bone density and muscle mass.
• Muscle mass can decrease by as much as 20% in just two weeks in space.
• Muscles related to posture, such as those in the neck and back, are most affected.
• Astronauts counteract this with resistive exercise devices, simulating weightlifting in zero gravity, and treadmills where they are strapped down. Peggy Whitson, who holds the record for the woman who has spent the most time in space, spent 45 minutes to an hour every day doing resistive exercise.

Fluid Redistribution

• On Earth, gravity pulls fluids downwards, requiring the heart to work to distribute them evenly.
• In space, fluids shift upwards, leading to a "puffy face" and potentially affecting the shape of the eyeball.
• 40% of astronauts experience lasting eye damage due to fluid accumulation around the eye.
• "Vacuum trousers" are used to counteract this by drawing fluid back down the body.

Radiation Exposure

• Earth's magnetic field protects us from radiation from the sun and space.
• Outside this field, astronauts are exposed to significantly higher levels of radiation.
• Radiation exposure can cause changes in genes and increase the risk of cancer.
• Astronauts wear Geiger counters to monitor their radiation exposure, which informs future mission decisions.
• Spacecraft and spacesuits incorporate shielding to minimize radiation exposure. The International Space Station has a layer of aluminum that reflects away some of the radiation.

Space Adaptation Sickness

• The fluid in the inner ear helps maintain balance.
• In space, this fluid moves differently, causing motion sickness.
• NASA used to train astronauts by spinning them in chairs to desensitize them to this effect.

Genetic and Aging Effects

• Studies on Russian twins and NASA astronaut Scott Kelly and his twin Mark Kelly have shown that space travel can affect genetics and potentially accelerate aging.
• Scott Kelly spent a year on the ISS while Mark Kelly remained on Earth.
• Upon returning, Scott was taller (due to spinal elongation), had lost body mass, and experienced genetic changes.
• While 93% of the genetic changes reverted after six months, some remained permanent.
• Scott's eyesight also changed, with lasting vision issues.

Countermeasures and Training

Exercise

• Astronauts exercise for up to two hours daily to combat muscle and bone loss.
• This includes resistive weight training and running on a treadmill while strapped down.

Shielding

• Spacecraft and spacesuits are designed with shielding to protect against radiation.
• The ISS has a layer of aluminum for radiation reflection.

Specialized Equipment

• Vacuum trousers help prevent fluid pooling in the head, reducing eye damage.

Training

• NASA uses a giant swimming pool with a replica of the ISS to simulate weightlessness.
• Astronauts wear weighted suits underwater to practice tasks in a weightless environment.
• Core strength training is emphasized to maintain stability in space.

Space Tourism

• Short space tourism trips (around ten minutes) are unlikely to cause long-lasting effects, although motion sickness is possible.
• The primary concern for longer missions is the cumulative effect of radiation exposure on genes and cancer risk.

Spacesuits

• Spacesuits are "tiny personal spacecraft" that protect astronauts during spacewalks.
• They provide oxygen, remove carbon dioxide, regulate temperature, and shield against radiation and micrometeorites.
• Spacesuits are pressurized and can weigh over 100kg on Earth, making movement difficult.
• Astronauts wear comfortable flight suits inside the space station.

Conclusion

Space travel poses significant challenges to the human body, including bone and muscle loss, fluid redistribution, radiation exposure, and space adaptation sickness. However, organizations like NASA employ various countermeasures, such as rigorous exercise regimens, shielding technologies, and specialized equipment, to mitigate these risks. Training programs, including underwater simulations and core strength exercises, prepare astronauts for the unique demands of space. While short space tourism trips pose minimal long-term health risks, extended missions require careful management of radiation exposure and its potential genetic consequences.