by The Artemis I mission, which recently completed a historic test flight around the moon, had no astronauts on board, but did have two very special passengers: Helga and Zohar, a pair of anatomically detailed simulated torsos, one of whom wore a special radiation protection vest for the trip. His mission? Measure radiation exposure in deep space and determine if a vest can help protect astronauts from the hidden dangers of space.
To learn more about the threat of space radiation and how to protect astronauts against it, we spoke with the CEO of the company that makes the vest, StemRad, as well as retired NASA astronaut Scott Kelly, a veteran of space station missions which is well known for its role in research on the health of astronauts.
The hidden dangers of radiation
Here on Earth, we are protected from dangerous radiation by the planet’s magnetosphere. The magnetic field around Earth traps radiation in two areas called the Van Allen belts, making it safe for us on the surface. But when astronauts go beyond low-Earth orbit, as they must to visit the moon (and other potential places in the solar system, like Mars), they are exposed to dangerous radiation.
Over the long term, exposure to this radiation, which consists of charged particles from the sun called solar winds, particles ejected in coronal mass ejections, and cosmic rays, can lead to a variety of health problems. Most significantly, radiation exposure increases the likelihood that someone will develop cancer or various degenerative diseases. That’s why NASA and other space agencies have a limit on the amount of radiation an astronaut can be exposed to during their lifetime.
The exposure that astronauts experience in an orbital environment like the International Space Station is much less than what they would experience on a trip to the moon, but it is still enough to affect the crew. “Sometimes you can see cosmic rays hitting your eyeball, and you realize it’s radiation and it’s also going through your body and through your eyes,” said Scott Kelly, who has served multiple missions on the International Space Station (ISS). “So it’s something you’re aware of.”
Venture beyond the magnetosphere
With NASA plans to send humans back to the moon and eventually send a crewed mission to Mars, the issue of radiation exposure is a big concern. Previous missions to the moon under the Apollo program lasted only a few days, and the astronauts were lucky not to experience any solar particle events that raised radiation levels in the time they were away. But for missions that last weeks or even months, we need a solution to protect astronauts from radiation.
That’s where the AstroRad vest comes into play. Made from a hydrogen-rich polymer material, the vest covers the pelvis and torso, shielding the most vulnerable organs from solar radiation. It may seem surprising that radiation protection can be applied only to certain parts of the body, and StemRad CEO Oren Milstein said many of the space industry insiders he pitched the idea to were also surprised. But full-body protection would be incredibly cumbersome, and the best protection would be something the astronauts could wear and still do their job.
Rather than an all-or-nothing approach, selective protection can balance effectiveness and practicality. If you can protect some of the more vulnerable organs, like the lungs or breast tissue, you can help keep people safe without overtaxing them.
Conceptualization of cumulative risks
As humans, we are often more used to thinking of risk in terms of immediate danger than as a cumulative process. Think about the difference between the fear of flying and the way we think about long-term health hazards like smoking. And when it comes to space, it’s natural to think of hazards in terms of rockets failing or spacecraft exploding, and it’s harder to imagine what cumulative radiation exposure looks like.
One of the key ways to reduce cumulative exposure is to create a shield that is good enough to offer some protection but is also comfortable enough for astronauts to wear. “We want something that not only protects you, but is something you want to wear,” Kelly said. She is a member of StemRad’s advisory board and has a particular understanding of the health issues facing astronauts, having been part of NASA’s groundbreaking twin study on the effects of spaceflight on the human body.
A vest protects parts of the body while allowing freedom of movement. And it can be effective even if it’s only used part of the time, as Milstein noted: “It’s not all or nothing in terms of duration of use. You can use the product only 70 percent of the time and it will still be very beneficial. You can take it off to shower or for strenuous activities like exercise. Because radiation is a cumulative thing.”
The importance of ergonomics
For a vest to be practical on spaceflight, astronauts must be able to move freely while wearing it. The AstroRad has been tested on the ISS by five astronauts who wore it day and night while performing their regular duties, to see if it affected their movements.
“For a lot of the vital things like eating and sleeping, time-consuming things, the vest was fine,” Milstein said. However, the vest prevented certain movements, such as raising the arms above the head, making tasks such as unloading a cargo vehicle difficult.
“Unloading a cargo vehicle is a challenge because everything floats,” Kelly said. “When you take a bunch of items out of a bag and you open the bag and they all start to float and you have to manage that, it becomes a challenge.” She said the challenge was mainly mental, as it requires astronauts to be extremely careful and methodical. But any impact of movement will make an already difficult task more difficult.
“Microgravity makes almost everything harder to do,” Kelly said.
To make the vest as flexible as possible without sacrificing protection, it’s made of thousands of hexagons of varying depths that fit into a mesh. This allows certain areas to have thicker protection than others (such as more protection over the lungs) while still being flexible enough to allow movement. The vest currently comes in two sizes, for male and female bodies, but there are plans for a modular system that would allow the vest to be shortened or lengthened to accommodate more bodies of different sizes.
Test the protection in a real world scenario
The tests conducted on the ISS AstroRad were to understand the comfort and fit of the vests for astronauts, but did not assess how much radiation was blocked. Therefore, the best way to test the effectiveness of the vest is to see it in a situation comparable to a real manned mission.
That’s why the Artemis I mission, which was unmanned, included the two dummies Helga and Zohar that are shaped like a torso and packed with detectors. The two torsos are designed to detect incoming radiation particles, and one will wear the vest so teams can see how effective the vest is in stopping this radiation. During the 25-day flight from Earth around the Moon and back, they will be exposed to the same radiation environment as astronauts on future missions.
“For the first time in history, we will be able to quantify radiation dose and radiation penetration into the body in deep space, something that has never been done before. And at the same time, validate a possible countermeasure,” Milstein said. “It’s going to be a treasure trove of data on human susceptibility to organ-level radiation within deep space.”
AstroRad’s focus is to protect against ionizing radiation, as it is the most dangerous to human health. But this test will also show if the vest is effective in stopping another type of radiation, called galactic cosmic rays. This background radiation is difficult to block, so the benefit is likely to be minor, but it’s all useful data for future protective measures.
The psychology of risk management.
Exploring space always carries some degree of risk, and astronauts are taught to compartmentalize this reality as part of their job. “He’s trained to focus on his job and the things he can control, and ignore everything else,” Kelly explained. “You are aware of the risk, but you don’t let it incapacitate you.”
Radiation is just one of the many risks astronauts face. Unlike immediate risks like launch failure, however, radiation is “this unknown risk,” Kelly said. “It’s a persistent risk that you’re exposing yourself to for the rest of your life.”
Space agencies have a moral obligation to keep their astronauts as safe as possible both in terms of immediate risks and in terms of long-term health impacts. For the Artemis missions to the moon and for future manned explorations beyond, radiation shielding will be an important part of that.
For Kelly, the key to her approach to risk management is balance, which means mitigating the risks that can be addressed and managing those that cannot. “We make it as safe as possible within reason,” she said. “If you wanted things to be 100% safe, you would never leave your house.”
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