Astronauts have been proposed to travel to Mars and Venus using asteroids as their means of transportation.

Protecting crew members from cosmic radiation is one of the most challenging tasks that must be addressed before scientists send humans on long-duration space missions. The health risks in space come from events known as cosmic radiation storms (solar proton events), which are triggered by powerful solar flares and plasma ejections from the Sun, as well as galactic cosmic rays—high-energy particles that arrive on Earth from the Galaxy.

Experts have long studied the effects of radiation on our bodies and have noted its detrimental impact on the central nervous system. For instance, Francis Cucinotta, the scientific lead of NASA's radiation effects research program, stated in one of his studies wrote that during spaceflight, the risks of health damage can double or even triple. Changes in cognitive functions occur, including deterioration in short-term memory, reduced motor functions, and behavioral changes that may affect a person's performance.

However, it is worth noting that a number of scientists hold a different viewpoint, and Russian researchers reported in one of their studies even about improvements in the cognitive abilities of animals after exposure to radiation equivalent to cosmic radiation.

Currently, the only method of protection against radiation in space is shielding. Special screens can reduce potentially harmful radiation levels to safe thresholds.

In 2011, a shielding curtain up to 10 centimeters thick was installed along the outer wall of one of the modules in the Russian segment of the ISS. According to domestic experts, this technology can decrease radiation exposure to the body by 20-60 percent.

However, installing screens on spacecraft intended for long-distance flights significantly increases the mission budget, which may deter potential investors and sponsors. Consequently, some researchers are exploring alternative solutions to the radiation problem.

One such idea was proposed by two Ukrainian astronomers, Arseniy Kasyanchuk and Volodymyr Reshetnyk from Taras Shevchenko National University. Their alternative involves traveling inside an asteroid, which they detailed in an article published on the electronic preprint archive arXiv.org. Some asteroids are sufficiently rich in silicates, which effectively absorb cosmic rays and solar wind particles.

The authors examined the orbits of 35,000 near-Earth asteroids to determine if any could be utilized for interplanetary flights before 2120. Specifically, they sought asteroids that could successively approach Earth, Mars, and Venus. The objects needed to be large enough for a spacecraft with crew onboard to land on them easily and then depart.

As a result, the astronomers compiled a list of 120 asteroids, some of which pass near the planets (Earth—Mars, Mars—Earth, Earth—Venus, Venus—Earth, Mars—Venus, Venus—Mars) regularly every two to three years, while others do so only once a century. This list includes two objects that successively approach three planets and ten with several consecutive pair approaches to the planets over 100 years.

According to Kasyanchuk and Reshetnyk's concept, astronauts would embark on a journey to one asteroid and return via another traveling in a different direction. Calculations suggest that the flight time to Mars or Venus would average up to 180 days.

“The advantage of this solution is that it allows visiting both planets in one mission. We calculated that in 2079, one asteroid will first approach Earth, then Venus, and finally Mars. This journey would take 230 days. In 2080, another asteroid will fly in the opposite direction, enabling the astronauts to return home safely,” Reshetnyk explained.

However, the project proposed by the Ukrainian astronomers is not without its challenges. There are numerous drawbacks, and not all the asteroids selected by the scientists are suitable for this kind of mission. For instance, to land on the surface of an object, pilots will need to choose an asteroid that is traveling at an appropriate speed, which is a complex task in itself.

Some asteroids travel at speeds of up to 30 kilometers per second, while others pass at speeds of two kilometers per second. Choosing the first option would require “an insane amount of fuel,” rendering the mission impractical.

The Ukrainian specialists suggested traveling inside the asteroid. Another issue arises: how to drill a tunnel within it? Humans have never attempted anything like this. From a technical standpoint, implementing such an idea is extremely challenging.

In any case, the project proposed by the Ukrainian astronomers is unlikely to be realized—at least within this century.