(ORDO NEWS) — Earth is the unique cradle of all life. Protected by its atmosphere and magnetic field, we can not think about radiation threats, except those that we create with our own hands.
However, all space exploration projects – near and far – invariably run into the problem of radiation safety. Space is hostile to life. We are not expected there.
The orbit of the International Space Station has been raised several times, and now its height is more than 400 km.
This was done in order to take the flying laboratory away from the dense layers of the atmosphere, where gas molecules still noticeably slow down the flight and the station loses altitude.
In order not to correct the orbit too often, it would be good to raise the station even higher, but this cannot be done.
Approximately 500 km from the Earth, the lower (proton) radiation belt begins. A long flight inside any of the radiation belts (and there are two of them) will be disastrous for the crews.
Nevertheless, it cannot be said that at the altitude at which the ISS is currently flying, there is no problem of radiation safety.
Firstly, in the South Atlantic there is the so-called Brazilian, or South Atlantic, magnetic anomaly. Here, the Earth’s magnetic field seems to sag, and with it, the lower radiation belt turns out to be closer to the surface. And the ISS still touches it, flying in this area.
Secondly, a person in space is threatened by galactic radiation – a stream of charged particles rushing from all directions and at great speed, generated by supernova explosions or the activity of pulsars, quasars and other anomalous stellar bodies.
Some of these particles are delayed by the Earth’s magnetic field (which is one of the factors in the formation of radiation belts), the other part loses energy in a collision with gas molecules in the atmosphere.
Something reaches the surface of the Earth, so that a small radioactive background is present on our planet absolutely everywhere.
On average, a person living on Earth who does not deal with radiation sources receives a dose of 1 millisievert (mSv) annually. An astronaut on the ISS earns 0.5–0.7 mSv. Daily!
“An interesting comparison can be made,” says Vyacheslav Shurshakov, head of the cosmonaut radiation safety department of the Institute of Biomedical Problems of the Russian Academy of Sciences, Candidate of Physical and Mathematical Sciences.
The allowable annual dose for a nuclear power plant employee is 20 mSv – 20 times more than an ordinary person receives.
For emergency responders, these specially trained people, the maximum annual dose is 200 mSv. This is already 200 times more than the usual dose and… almost the same as an astronaut who has worked for a year on the ISS receives.
Currently, medicine has established the maximum dose limit, which during a person’s life cannot be exceeded in order to avoid serious health problems.
This is 1000 mSv, or 1 Sv. Thus, even a nuclear power plant employee with his standards can work quietly for fifty years without worrying about anything.
The astronaut will exhaust his limit in just five years. But even after flying for four years and gaining its legal 800 mSv, it is unlikely to be allowed on a new flight of a year duration, because there will be a threat of exceeding the limit.
“Another factor in the radiation hazard in space,” explains Vyacheslav Shurshakov, “is the activity of the Sun, especially the so-called proton emissions. At the time of release, an astronaut on the ISS can receive an additional 30 mSv in a short time.
It is good that solar proton events occur rarely – 1-2 times per 11-year cycle of solar activity. It is bad that these processes occur stochastically, randomly, and are difficult to predict. I do not remember such that we would have been warned in advance by our science about the coming blowout.
Usually things are different. Dosimeters on the ISS suddenly show an increase in the background, we call solar specialists and get confirmation: yes, there is anomalous activity of our star. It is precisely because of such sudden solar proton events that we never know for sure
Particles that drive you crazy
Radiation problems for crews going to Mars will begin even at the Earth. A ship weighing 100 tons or more will have to be accelerated in near-Earth orbit for a long time, and part of this trajectory will pass inside the radiation belts.
It is no longer hours, but days and weeks. Further – going beyond the magnetosphere and galactic radiation in its original form, a lot of heavy charged particles, the impact of which under the “umbrella” of the Earth’s magnetic field is little felt.
“The problem is,” says Vyacheslav Shurshakov, “that the influence of particles on the critical organs of the human body (for example, the nervous system) is little studied today. Perhaps radiation will cause memory loss in an astronaut, cause abnormal behavioral reactions, aggression.
And it is very likely that these effects will not be dose-specific. Until enough data has been accumulated on the existence of living organisms outside the Earth’s magnetic field, it is very risky to go on long-term space expeditions.
When radiation safety experts suggest that spacecraft designers strengthen biosecurity, they answer with a seemingly quite rational question: “What is the problem? Did any of the astronauts die from radiation sickness?
Unfortunately, the doses of radiation received on board not even the starships of the future, but the ISS familiar to us, although they fit into the standards, are not at all harmless.
American data clearly show that cosmic radiation increases the risk of cataracts, clouding of the lens. Blood studies of astronauts demonstrate an increase in chromosomal aberrations in lymphocytes after each space flight, which is considered a tumor marker in medicine. In general, it was concluded that
One of the “strong” arguments of the supporters of the “lunar conspiracy” is the assertion that crossing the radiation belts and being on the Moon, where there is no magnetic field, would cause the inevitable death of astronauts from radiation sickness.
American astronauts really had to cross the Earth’s radiation belts – proton and electron.
But this happened within only a few hours, and the doses received by the Apollo crews during the missions turned out to be significant, but comparable to those received by the old-timers of the ISS.
“Of course, the Americans were lucky,” says Vyacheslav Shurshakov, “after all, not a single solar proton event occurred during their flights.
If this happened, the astronauts would receive sublethal doses – no longer 30 mSv, but 3 Sv.
Wet your towels!
“We, experts in the field of radiation safety,” says Vyacheslav Shurshakov, “ insist that the protection of crews be strengthened. For example, on the ISS, the most vulnerable are the astronauts’ cabins, where they rest.
There is no additional mass there, and only a metal wall a few millimeters thick separates a person from outer space. If we bring this barrier to the water equivalent accepted in radiology, this is only 1 cm of water.
For comparison: the earth’s atmosphere, under which we shelter from radiation, is equivalent to 10 m of water. We recently proposed to protect the astronauts’ cabins with an additional layer of water-soaked towels and napkins, which would greatly reduce the effects of radiation.
Medications are being developed to protect against radiation – however, they are not yet used on the ISS. Maybe, in the future, by means of medicine and genetic engineering, we will be able to improve the human body in such a way that its critical organs are more resistant to radiation factors.
But in any case, without the close attention of science to this problem, deep space flights can be forgotten.”
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