Of those 34 dangers, three are potential showstoppers: radiation, gravity (or lack thereof), and the necessity for surgical procedure or an advanced medical process.
The Gravity of the Scenario
Let’s discover the gravity subject.
Some science fiction writers within the mid-Twentieth century speculated that zero gravity could be life-giving: blood would movement extra simply; arthritis could be a factor of the previous; again ache could be cured for good; and ageing itself would decelerate. So, convey grandma alongside for the trip. We had hints from early within the area program that such a rosy state of affairs wasn’t true. Astronauts returned from just some days of weightlessness feeling weak. However they recovered; and lots of thought, effectively, possibly it isn’t so dangerous. Then we spent extra time in area. Russians on the Mir area station for months appeared to have some critical, extended well being points on their return. The Russians had been tight-lipped in regards to the well being of their cosmonauts, although, so we by no means knew for positive. Many of those cosmonauts, championed as heroes, had been hardly ever seen in public after their return. It was the ISS missions that drove dwelling the message: long-term publicity to zero gravity is detrimental to human well being on many ranges. Kudos to NASA for that.
Earlier than I proceed, I ought to first outline some phrases. Zero gravity, nevertheless visually handy, generally is a misnomer within the context of near-earth exercise. The astronauts on the ISS should not dwelling within the absence of gravity. Fairly, they’re in free-fall, ceaselessly falling over the horizon and lacking the Earth. The ISS and different satellites should not floating in area as a result of they’ve escaped the pull of Earth’s gravity; they keep up there due to their terrific horizontal pace. The ISS is shifting at 17,500 miles per hour. If, someway, it got here to a whole cease, it will fall straight all the way down to Earth, and down would come astronaut, cradle and all. The Earth’s gravitational power, in actual fact, retains the shifting satellites in orbit as a superbly balanced counterforce, in a downward movement, to the lateral movement set in place in the course of the launch. With out the Earth’s gravitational power (if the Earth immediately, magically, disappeared), the satellites would shoot off in a straight line. Subsequently, extra correct phrases for describing the dearth of sensation of gravity aboard the ISS are microgravity and weightlessness. But, even these phrases are neither good nor synonymous. Astronauts on the ISS have weight, about 90 p.c of their weight on Earth, which is just about 200 miles beneath their ft. They’d be a lot lighter on the Moon, truly, at nearly 16 p.c of their weight. Absolute zero gravity will not be attainable, as a result of gravity is the power of attraction between any two objects. However in deep area, removed from the gravitational tug of any moon, planet, or star, gravity is attenuated to nearly zero. I have a tendency to make use of the phrases zero gravity, micro-gravity, and weightlessness interchangeably within the context of area journey.
Our understanding of gravity’s impact on the physique has solely two knowledge factors: one and 0. On Earth, we stay with a gravitational power of 1G. On the ISS, astronauts stay in 0G. We actually don’t find out about something in between. Air power pilots may speed up their jets so shortly that they expertise forces of 5G or larger, which typically causes them to black out. That’s 5 occasions the power of regular Earth gravity, which pushes blood out of their brains. However such forces usually final only some seconds; the pilots aren’t dwelling in a hyper-gravity setting. And anyway, we don’t care an excessive amount of about forces larger than 1G as a result of each place we wish to go in our Photo voltaic System—L2 orbit, the Moon, Mars, and so forth—has a gravitational power lower than 1G.