Space exploration presents numerous challenges, and among the most important concerns for human spaceflight is radiation protection. Once a spacecraft leaves Earth’s atmosphere and the protective influence of its magnetic field, astronauts are exposed to significantly higher levels of radiation than on Earth. The two primary sources of harmful radiation in space are solar particle events (SPEs) and galactic cosmic rays (GCRs). Extended exposure to these forms of radiation poses significant health risks to astronauts, including cancer, damage to the central nervous system, and long-term effects such as cataracts and cardiovascular disease.

Because future missions will venture farther from Earth, such as potential manned missions to Mars, protecting astronauts from radiation has become a focal point for space agencies worldwide. This article provides an in-depth look at the various radiation protection methods being used or developed for human spacecraft, including the latest results from the Artemis I mission and advancements such as the Israeli AstroRad vest.

Types of Space Radiation

Understanding the two primary sources of space radiation is crucial to designing effective protection systems.

• Solar Particle Events (SPEs): Solar flares and coronal mass ejections (CMEs) generate SPEs, releasing high-energy protons and electrons from the Sun. While SPEs are infrequent, they can be highly intense, delivering a potentially dangerous dose of radiation over a short period.
• Galactic Cosmic Rays (GCRs): GCRs are high-energy particles, primarily protons, originating from outside the solar system. They result from supernova explosions and other cosmic events. GCRs are particularly hazardous because they are highly energetic, persistent, and capable of penetrating most shielding materials. Their impact becomes more significant the farther a spacecraft is from Earth’s magnetic field.

Shielding Methods

Passive Shielding

The most widely used and practical method for radiation protection in spacecraft today is passive shielding. This approach uses physical barriers to absorb or deflect radiation particles.

Material Shielding

The effectiveness of passive shielding largely depends on the choice of materials. Different materials interact with radiation in various ways, with some offering better protection against certain types of radiation. Some of the most commonly used materials include:

• Aluminum: This metal is often used in the construction of spacecraft due to its durability, low cost, and ease of manufacture. However, while aluminum provides basic protection from SPEs, it is less effective against GCRs. Additionally, when struck by high-energy cosmic rays, aluminum can produce secondary radiation, such as neutrons, which may pose additional risks to astronauts.
• Polyethylene: Polyethylene is highly effective at blocking GCRs, particularly due to its high hydrogen content. Hydrogen-rich materials are better at absorbing the energy from cosmic rays without producing harmful secondary particles. NASA has explored using high-density polyethylene as an alternative to traditional metal-based shields, as it reduces both the weight of the spacecraft and the exposure to secondary radiation.
• Water: Water, also rich in hydrogen, serves as an effective radiation shield. It has been proposed that water could be stored in tanks around the crew compartments or living quarters to create a barrier that both protects astronauts from radiation and provides a practical utility in space. In long-duration missions, water could also be reused and recycled.
• Borated Plastics: Boron-infused materials are currently being investigated for their potential to absorb neutrons, which are secondary radiation particles often generated when GCRs impact other shielding materials. Borated plastics are lightweight, making them an attractive option for spacecraft where weight is a major consideration.

Thickness and Configuration

One important consideration in passive shielding is the thickness of the shielding material. While thicker shields offer better protection, they also add considerable weight to the spacecraft, a significant drawback due to the high cost of launching additional mass into space. Engineers are developing optimized configurations where the most critical areas of the spacecraft, such as the crew cabin, are equipped with thicker shielding, while less crucial areas have lighter protection. This selective distribution of shielding helps balance protection with cost-efficiency.

Active Shielding

Active shielding represents a more advanced concept that could one day offer better radiation protection than passive methods alone. This method uses electric or magnetic fields to deflect incoming charged particles before they reach the spacecraft, similar to the way Earth’s magnetic field protects the planet from solar and cosmic radiation. While promising, these technologies are still in development and face numerous technical challenges.

Magnetic Shielding

Inspired by Earth’s magnetosphere, magnetic shielding would create an artificial magnetic field around the spacecraft to deflect charged particles, such as those from solar particle events. Theoretically, this could provide significant protection without the need for heavy physical shields. One proposal involves using superconducting magnets to generate strong magnetic fields. However, maintaining superconducting states in space and dealing with the massive energy requirements pose significant hurdles. There are also concerns that these magnetic fields could interfere with the spacecraft’s systems or pose health risks to astronauts.

Electrostatic Shielding

Another active shielding method being explored is electrostatic shielding. This concept uses an electric field to repel positively charged particles, such as protons from SPEs. While the energy requirements for electrostatic shielding are lower than for magnetic fields, developing a system capable of providing comprehensive protection is still a challenge. As with magnetic shielding, this approach remains in the experimental phase and is not yet ready for use in human spaceflight.

Biological Protection

In addition to shielding the spacecraft itself, researchers are exploring ways to protect astronauts on a biological level. This approach includes pharmaceutical treatments and possibly genetic interventions to enhance the body’s resilience to radiation exposure.

Pharmaceuticals

Several classes of drugs are under investigation for their potential to protect astronauts from the harmful effects of radiation. These include:

• Radioprotectors: These are drugs that protect healthy cells from radiation damage by preventing or mitigating DNA damage. Amifostine is one example of a radioprotector already used in cancer treatment to shield healthy cells from the effects of radiation therapy. Research is ongoing to determine if similar drugs could be used to protect astronauts.
• Radiomitigators: Taken after radiation exposure, radiomitigators help repair damaged tissues and reduce the long-term effects of radiation. Scientists are exploring the use of antioxidants and other compounds that can reduce oxidative damage caused by radiation.

While these drugs are still in the early stages of research, they represent a promising avenue for reducing the health risks associated with long-duration space travel.

Genetic Engineering

Though still largely speculative, genetic engineering could offer a future method of increasing human resilience to radiation. By modifying certain genes that regulate DNA repair and cellular resistance to radiation, it might be possible to make astronauts more resistant to radiation exposure. However, this approach is decades away from practical application and raises ethical questions about genetic modification.

Spacecraft Design Strategies

In addition to material and active shielding, the design of the spacecraft itself can contribute significantly to radiation protection.

Habitat Placement and Storm Shelters

Strategic placement of living quarters within the spacecraft can reduce radiation exposure. By positioning crew habitats in the center of the spacecraft and surrounding them with storage tanks, water supplies, or fuel, engineers can create a makeshift radiation shield. This approach, often referred to as creating “storm shelters,” provides temporary protection during solar flares or SPEs. These areas would have enhanced shielding and could serve as a safe haven for astronauts during high-radiation periods.

Rotating Habitats

Theoretical designs for rotating space habitats, such as those proposed by Gerard O’Neill, may offer opportunities for built-in radiation protection. Rotating structures could use centrifugal force to generate artificial gravity, but their design also allows for the inclusion of thick external walls to block radiation. In some proposals, these rotating habitats would use layers of materials such as water or hydrogen-rich compounds to further enhance protection.

Radiation Monitoring and Alerts

Radiation protection in space also depends on real-time monitoring of radiation levels, allowing astronauts and mission control to react quickly to changes in the space environment.

Radiation Sensors

Spacecraft are equipped with radiation sensors that measure the intensity of radiation around the spacecraft. These sensors are critical for warning astronauts when they are at risk of excessive radiation exposure. In the event of an SPE, these sensors can provide early warnings, allowing astronauts to take cover in shielded areas of the spacecraft.

Space Weather Forecasting

Monitoring solar activity is crucial for predicting radiation risks. Space agencies use satellite data to observe the Sun’s behavior and predict when solar flares or coronal mass ejections are likely to occur. This information helps mission planners schedule activities like extravehicular activities (EVAs) when radiation levels are expected to be lower.

Orion Artemis I Mission

NASA’s Artemis I mission marked a significant step in testing the capabilities of the Orion spacecraft, designed to take humans back to the Moon and beyond. As an uncrewed mission, Artemis I provided an ideal platform to measure the space radiation environment in deep space, beyond Earth’s magnetosphere. Orion carried multiple radiation sensors, including Crew Personal Active Dosimeters (CPADs) and phantoms (human mannequins embedded with sensors), to monitor radiation levels throughout the mission.

The phantoms, named Helga and Zohar, were equipped with sensors designed to assess radiation exposure in different parts of the body. Zohar was fitted with the AstroRad vest to test its effectiveness in protecting against space radiation. The mission revealed that the AstroRad vest significantly reduced radiation exposure in sensitive organs, marking an important milestone for astronaut safety on future deep space missions.

Radiation data from Artemis I showed that during its journey around the Moon, Orion encountered moderate radiation levels, though no major solar storms occurred. This provided valuable baseline data for understanding radiation exposure in cislunar space. The data also highlighted areas within the spacecraft where localized radiation shielding could be improved.

Israeli Radiation Protection Vest: AstroRad

One of the most promising developments in radiation protection for astronauts is the AstroRad radiation vest, developed by the Israeli company StemRad. The vest is designed to protect astronauts from harmful radiation exposure, particularly during deep space missions where exposure to SPEs and GCRs is much higher than in low Earth orbit.

Design and Functionality

The AstroRad vest is designed to protect the body’s most vulnerable organs, such as the bone marrow, lungs, stomach, intestines, and ovaries, without hindering an astronaut’s movement. The vest uses a combination of advanced materials and modular design to provide flexible, comfortable protection that can be worn during high-radiation periods, such as solar storms.

Experiments and Testing

The AstroRad vest was tested aboard the Orion spacecraft during the Artemis I mission, where one of the test dummies (named Zohar) was equipped with the vest to assess its effectiveness in real-world conditions. This experiment is part of the Matroshka AstroRad Radiation Experiment (MARE), a collaboration between NASA, the German Aerospace Center (DLR), and the Israel Space Agency. MARE aims to evaluate the vest’s ability to reduce radiation exposure in critical organs, especially during extended deep-space missions.

Preliminary results from the Artemis I mission are encouraging, showing that the AstroRad vest effectively reduces radiation exposure to the sensitive organs of the human body. Further testing will be required during future crewed Artemis missions to validate these findings and determine how the vest can be incorporated into standard mission protocols.

Summary

Protecting astronauts from space radiation is one of the most important challenges in the design and planning of human space missions. Current methods rely heavily on passive shielding using materials like polyethylene, aluminum, and water. At the same time, experimental techniques like active shielding, biological countermeasures, and wearable protection such as the AstroRad vest are being explored for future missions. Innovative spacecraft design strategies, such as habitat placement and modular shielding, also provide valuable protection.

Space missions such as Artemis I have provided crucial data on radiation exposure in space, shaping the methods used to protect astronauts. As space agencies prepare for long-duration missions, advancements in radiation protection technologies will be essential for ensuring the safety and health of astronauts.