Safe to send humans to Mars if travel lasts less than four years


Writing of the Technological Innovation Site – 08/27/2021

It’s no use building ships with too thick armor because the net effect would be harmful.
[Imagem: Steve Bidmead/Pixabay]

Maximum time for a trip to Mars

Space agencies and private companies have plans to send humans to Mars, but aside from technical and economic questions, one question remains: is it safe to send humans – in terms of the effects on their health – on a trip to the red planet?

A group of experts from four institutions in the US, Russia and Poland were willing to bring together the best fundamentals currently available to try to answer this question.

The answer “Yes”, but followed by an important “but”.

According to Mikhail Dobynde and his colleagues, humans should be able to travel safely to Mars, and return, provided the spacecraft has sufficient armor and the round-trip is shorter than approximately four years.

Also, the timing of the trip should be well calculated, because it really makes a difference: Researchers have determined that the best time for a rocket to leave Earth for Mars is when solar activity is at its peak, known as solar maximum.

The researchers modeled the different types of cosmic rays that astronauts will be subjected to outside of Earth’s magnetosphere.
[Imagem: Mikhail I. Dobynde et al. – 10.1029/2021SW002749]

Maximum sun protection

Although this second condition seems contradictory, given that the solar maximum marks the period of greatest radiation emission from our star, the fact that this increased solar radiation offers a greater level of protection to the inner Solar System against the energetic and more dangerous particles emitted by distant stars and galaxies.

The two main types of hazardous radiation in space are solar energy particles and galactic cosmic rays. The intensity of each depends on solar activity, with the intensity of solar energy particles being greatest during the maximum of the 11-year solar cycle. Particularly in the six to 12 month period around the peak of solar activity, our star’s activity is strong enough to reduce to its minimum the galactic cosmic rays that reach Mars and Earth.

And, the team calculates, at this minimum level of cosmic radiation, the armor currently available for spacecraft will be able to protect the astronauts during their voyage and their stay on Mars.

The biggest concern is the cumulative effect of radiation.
[Imagem: Mikhail I. Dobynde et al. – 10.1029/2021SW002749]

cumulative radiation

The researchers used geophysical models of particle radiation for a solar cycle, combined with models of how the radiation would affect spacecraft and its human passengers, including its varied effects on different organs of the body.

The modeling concluded that building the spacecraft capsule out of a material thick enough could help protect astronauts from radiation; however, if the shield is too thick, it can even increase the amount of secondary radiation that astronauts will be exposed to.

However, because of the cumulative effect of radiation that beats shields and armor, hitting astronauts all the time, the team calculates that it is unsafe to be in space for more than four years.

This makes a round trip to Mars a feasible goal. In fact, with current spacecraft and rocket technology, a trip to Mars would take about nine months; therefore, depending on the timing of launch and available fuel, it is plausible that a human mission could reach the planet and return to Earth in less than two years.


Article: Beating 1 Sievert: Optimal Radiation Shielding of Astronauts on a Mission to Mars
Authors: Mikhail I. Dobynde, Yuri Y. Shprits, A. Yu. Drozdov, J. Hoffman, J. Li
Magazine: Space Weather
DOI: 10.1029/2021SW002749

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