astronaut space walk

How are astronauts protected from space radiation?

Last Updated: September 8, 2021

Scientists have long known that radiation levels are higher in space than what we experience on the Earth’s surface.

During the Apollo missions between 1969 and 1972, astronauts recorded the cumulative exposure they received through a dosimeter. However, it was not until 2019 that a detailed breakdown of radiation levels on the lunar surface and in space would be recorded by China’s Chang’e 4 moon mission.

The mission’s rover and lander duo were specially designed to simulate the same level of protection an astronaut inside a spacesuit would receive, and the results highlighted just how dangerous the levels of radiation are on the lunar surface.

What is space radiation and where does it come from?

The increased radiation exposure faced by astronauts comes from both solar and cosmic radiation. Radiation – a form of energy that is emitted or carried in the form of rays, electromagnetic waves, and particles – exists in two forms: ionizing and non-ionizing. While non-ionizing radiation can be damaging it is easily shielded against. Ionizing radiation, on the other hand, is harder to shield against. This is the form of radiation astronauts are exposed to.

Solar radiation, consisting of charged particles emitted by the sun, is constant. Events like solar flares can provide bigger bursts of this energy and in rare events be strong enough to distort radio signals and GPS on Earth. Galactic cosmic rays, however, originate from distant supernovas exploding outside of our solar system. These atoms are highly energised and travel close to the speed of light which makes them highly penetrative and hard to shield against. This cosmic radiation contributes approximately 75% of the total radiation measured on the lunar surface.

Solar and cosmic radiation are examples of ionizing (high energy) radiation. This form of radiation is comprised of highly energetic particles which change the charge of atoms it comes into contact with. This is difficult to shield from as it has the ability to move through and alter substances it interacts with – such as the human body. While we are largely protected from much of the electromagnetic cosmic radiation by the magnetic field and atmosphere of Earth, astronauts have limited protection and are more at risk from the effects of space radiation

solar radiation

Radiations coming from the Sun is a constant threat for astronauts on the ISS.

What are the health risks for astronauts exposed to space radiation?

The interaction of ionizing radiation on living organisms can lead to harmful biological effects such as an increased risk of cancer, cardiovascular disease, heart disease and, in extreme cases, acute radiation sickness. This is largely due to the biological damage ionizing radiation can have on human cells and deoxyribonucleic acid (DNA). Reducing this biological risk of space travel is a priority.

Not all astronauts have an equal risk of harmful radiation. Although factors such as radiation dose and area of the body exposed can impact the level of biological damage received, NASA has identified three main factors to focus on when trying to mitigate the impact of radiation of the human body: altitude above Earth, the solar cycle, and the individual’s susceptibility – for example, women and younger crew members are at a greater risk of experiencing dangerous levels of radiation.

How are the astronauts onboard the ISS protected from space radiation?

Astronauts aboard the International Space Station orbit at a low enough altitude to be provided protection by the Earth’s 300,000-mile radius magnetic field. Although the field offers some protection, the crew still experience higher radiation doses than those of us on Earth and finding practical solutions to protect them is a constantly evolving discipline. 

Although radiation levels can be forecast by studying the 11-year cycle of solar activity, unexpected short-term events like solar flares are sporadic and cannot be accurately predicted. In a bid to prevent lethal radiation exposure from these sudden events NASA have a dedicated team who monitor space weather and sun flares – if there is a notable increase in solar energetic particles activities that require leaving the space station are postponed and, in some cases, astronauts are advised to seek refuge in designated storm shelters, such as the Zvezda and the Destiny modules.

These shelters work by creating extra levels of mass such as TeSS Polyethylene, (“Radiation Bricks”) for the energetic particles to travel through and deposit energy into before reaching the crew, reducing their exposure to harmful levels of radiation. Although purpose-built storm shelters are difficult to incorporate into ship design as it requires adding extra material and therefore increased fuel to launch, NASA is looking into ways astronauts can utilise items already available to them. Currently, shelters constructed from stowage bags are being trialled to protect astronauts from the intense radiation while in orbit.

Long duration deep-space exploration, however, poses a different set of problems.

The Destiny laboratory module can provide some protection against space radiation during solar wind outbursts. Credit: Canadian Space Agency

How will astronauts be protected from radiation on the Moon?

NASA is currently developing strategies to protect astronauts aboard the Orion spacecraft during Artemis I, NASA’s next manned mission to the moon set to launch in 2024. The overarching aim is to establish a human presence on the moon and, ultimately, Mars; developing countermeasures against long term exposure to radiation is a priority to achieve this. 

Space radiation studies have shown that the levels by the crew of Orion will be much higher than those experienced by astronauts aboard the International Space Station – radiation on the lunar surface is 2.6 times higher than in Earth’s orbit and 200 times higher than what we experience on Earth’s surface. Astronauts on the Artemis I mission will not only need to be protected against dangerous radiation while in flight, but also in the high radiation environment of the moon without the extra level of protection provided by a spacecraft. 

Creative countermeasures such as wearable vests containing water, or electrically charged surfaces to deflect radiation, are currently being developed but NASA also has another, more pragmatic answer – creating barriers with lunar soil or rock over shelters.

The Artemis I mission aims to collect an abundance of data to assist NASA in safely sending human explorers to Mars. As the journey is much longer the crew will face higher levels of radiation exposure and, unlike Earth, Mars has no magnetic field to protect astronauts once they have reached its orbit. 

The creative uses of existing equipment and the development of innovative solutions will help to protect these future astronauts on the longest journey humanity has ever undertaken.

Space agencies are considering the use of moon regolith as a form of shielding against radiation. Credits: ESA/Foster and Partners

Written by Amy Donnelly

I am a lover of folklore, archaeology & anthropology. When I am not studying history, I like to learn about space exploration and imagine what kind of future awaits us amongst the stars. Follow me on Instagram!

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