Spaceflight and human health
Spaceflight changes human physiology, and long missions in space call for planning against medical contingencies and for the supplies a crew will need.
Space as a severe environment
In one physician's view, the problem in space flight is that people do complex things in severe environments, and space is probably the most severe of them. So, in that view, similar conditions need to be simulated in the next best severe environments, such as microgravity and high pressure, and devices need to be tested to see whether they work in such an environment.
Changes in physiology
On earth, because of gravity, the heart pumps blood to the head. In space, where there is no gravity, an even amount of blood circulates to the head and the feet, and the heart recognises the difference and adjusts. Astronauts returning to earth may experience dizziness on standing up, and medications to improve vascular tone are then used.
Astronauts lose 1% to 2% of bone mass per month in space, approximately what most people lose in a year on earth, and this increases the risk of fractures and of kidney stones.
Medical issues on long missions
The medical issues to be addressed on long-term missions also include differences in sensorimotor, sleep and circadian responses; the effects of radiation; the impact on microorganisms; and the psychological state of the astronauts. Health threats in long-duration space flight include progressive disease, traumatic injury, nutritional deficiency, sleep disturbance, biohazards in the spacecraft environment, psychiatric or cognitive crisis, and failure of life support.
Planning for long missions
The changes in physiology and the medical issues to be addressed on long missions mean that many decisions must be made. A trip to Mars is long, and water, waste, sweat and urine need to be recycled throughout it. So food, water, medications and other supplies must be carefully planned and organised.
Sending people on long-term space missions requires cooperation and coordination among several people and organisations, which is why, in one ethicist's view, only governments and not private industry can undertake such a task.
Contingency training
In the Challenger disaster most of the astronauts' emergency air packs were found to have been activated, in what one physician called a valiant but vain attempt to keep the pilot conscious. The same physician called even the Columbia disaster not salvageable, and holds that NASA should be prepared for similar situations in future.
Since these disasters, astronauts have been trained for numerous contingencies simulating different disaster scenarios, in intensive full-day courses beginning at six in the morning. The medical personnel involved in contingency training include doctors, nurses and paramedics trained in special techniques, such as intubating an astronaut wearing a helmet. They are equipped with a complete medical kit containing intravenous fluids, cardiac life support, a locked narcotics box and a handheld ultrasound machine.