Astronauts experience up to 20% atrophy in some muscle groups over 6 months despite 2.5hrs of daily exercise, which comes out of time that would be better used on their heavy workload of scientific experiments, or the leisure of enjoying spaceflight.

In microgravity, astronauts experience bone density loss of 1 - 2% per month, particularly in weight-bearing bones like the spine and hips, due to reduced mechanical stress. This increases fracture risk and requires exercise and potential biotech interventions to mitigate.

Prolonged spaceflight can impair cognitive function due to microgravity, cosmic radiation, and isolation, leading to issues like reduced attention, memory deficits, and slower reaction times. These challenges highlight the need for protective biotech interventions to support astronaut brain health during extended missions.

Spaceflight can cause vision impairment, known as Spaceflight-Associated Neuro-ocular Syndrome (SANS), due to microgravity-induced fluid shifts that increase intracranial pressure, affecting the optic nerve and retina.

While these are the major physiological challenges of spaceflight, there are many more minor ones to solve as well.