How dangerous is cosmic radiation for humans?

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

The earth is a unique cradle of all living things. 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 projects of space exploration - near and far - invariably run up against the problem of radiation safety. Space is hostile to life. We are not expected there.

The orbit of the International Space Station has been lifted several times, and now its height is over 400 km. This was done in order to move the flying laboratory away from the dense layers of the atmosphere, where gas molecules still quite noticeably slow down the flight and the station is losing 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. The lower (proton) radiation belt begins about 500 km from the Earth. A long flight inside any of the radiation belts (and there are two of them) will be disastrous for the crews.

Cosmonaut-liquidator

Nevertheless, it cannot be said that there is no radiation safety problem at the altitude at which the ISS is currently flying. First, in the South Atlantic there is a 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, man in space is threatened by galactic radiation - a stream of charged particles rushing from all directions and at a tremendous speed, generated by supernova explosions or by the activity of pulsars, quasars and other anomalous stellar bodies. Some of these particles are retained by the Earth's magnetic field (which is one of the factors in the formation of radiation belts), while the other part loses energy in collisions 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 sources of radiation receives a dose of 1 millisievert (mSv) annually. An astronaut on the ISS earns 0.5–0.7 mSv. Daily!

Radiation belts

The Earth's radiation belts are regions of the magnetosphere in which high-energy charged particles accumulate. The inner belt consists mainly of protons, the outer one consists of electrons. In 2012, another belt was discovered by the NASA satellite, which is located between the two known ones.

“An interesting comparison can be made,” says Vyacheslav Shurshakov, head of the department of radiation safety of cosmonauts at the Institute of Biomedical Problems of the Russian Academy of Sciences, Candidate of Physical and Mathematical Sciences. - The permissible annual dose for a nuclear power plant employee is considered to be 20 mSv - 20 times more than an ordinary person receives. For emergency response specialists, these specially trained people, the maximum annual dose is 200 mSv. This is already 200 times more than the usual dose and … practically the same amount as an astronaut who has worked on the ISS for a year gets."

Currently, medicine has established a maximum dose limit, which cannot be exceeded during a person's life in order to avoid serious health problems. This is 1000 mSv, or 1 Sv. Thus, even an NPP employee with his standards can work quietly for fifty years without worrying about anything.

The astronaut, on the other hand, will exhaust his limit in just five years. But, even having flown for four years and gaining his legal 800 mSv, he will hardly be allowed on a new flight of a one-year duration, because there will be a threat of exceeding the limit.

“Another factor of radiation hazard in space, - explains Vyacheslav Shurshakov, - is the activity of the Sun, especially the so-called proton emissions. At the moment of an ejection, in a short time, an astronaut on the ISS can receive an additional 30 mSv. It is good that solar proton events rarely occur - 1–2 times in an 11-year solar activity cycle. It is bad that these processes occur stochastically, in a random order, and are difficult to predict.

I do not remember such that we would have been warned in advance by our science about the impending release. This is usually not the case. Dosimeters on the ISS suddenly show an increase in the background, we call specialists on the Sun and receive confirmation: yes, there is anomalous activity of our star. It is because of such sudden solar proton events that we never know exactly what dose the astronaut will bring with him from the flight."

Crazy particles

Radiation problems for crews going to Mars will begin as early as Earth. A ship weighing 100 tons or more will have to be accelerated for a long time in low-earth orbit, and part of this trajectory will pass inside the radiation belts. These are 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 felt little.

“The problem is,” says Vyacheslav Shurshakov, “that the effect of particles on critical organs of the human body (for example, the nervous system) has been little studied today. Perhaps radiation will cause the astronaut to lose memory, cause abnormal behavioral reactions and aggression. And it is very likely that these effects will not be dose-related. 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 space expeditions."

When radiation safety experts suggest that spacecraft designers increase biosecurity, they answer a seemingly quite rational question: “What's the problem? Did any of the cosmonauts die of radiation sickness? Unfortunately, the radiation doses received on board not even the starships of the future, but the usual ISS, although they fit into the standards, are not at all harmless.

For some reason, Soviet cosmonauts never complained about their eyesight - apparently, they were afraid for their careers, but American data clearly show that cosmic radiation increases the risk of cataracts and lens opacities. Blood tests of astronauts show 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 receiving an allowable dose of 1 Sv during a lifetime shortens life by three years on average.

Lunar risks

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 electronic. But this happened for 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 happened during their flights. If this happened, astronauts would receive sublethal doses - not 30 mSv, but 3 Sv.

Get your towels wet

“We, specialists in the field of radiation safety,” says Vyacheslav Shurshakov, “insist that the protection of the crews be strengthened. For example, on the ISS, the most vulnerable are the cosmonauts' cabins, where they rest. There is no additional mass there, and only a metal wall several millimeters thick separates a person from outer space. If we reduce this barrier to the water equivalent accepted in radiology, it is only 1 cm of water.

For comparison: the Earth's atmosphere, under which we hide from radiation, is equivalent to 10 m of water. We recently proposed to protect astronauts' cabins with an additional layer of water-soaked towels and napkins, which would greatly reduce the effects of radiation. Drugs are being developed to protect against radiation, although they are not yet used on the ISS.

Perhaps, in the future, using the methods of medicine and genetic engineering, we will be able to improve the human body so that its critical organs are more resistant to radiation factors. But in any case, without close attention of science to this problem, one can forget about long-distance space flights."