Fly me to the moon: how plastics contribute to radiation protection in space

When it comes to the use of plastics in space, you probably first think of spacesuits or lightweight components. But there is another application: radiation protection. Space radiation is a risk to humans that should not be underestimated. The MARE experiment aims to determine this risk in order to develop protective measures for future space flights.

Did you know that the American flag that Neil Armstrong and Buzz Aldrin stuck into the surface of the moon on July 21, 1969 was made of nylon? The two astronauts' spacesuits were also lined with plastic. Since that historic day, plastics have become increasingly important in space. Components made of high-tech plastics can withstand extreme temperatures and are also lighter than other materials. Flexible plastic films are used to coat solar cells for powering satellites. And as foam, they can absorb sound and protect sensitive electronic systems in rockets.

Normally, such phantoms are used in cancer therapy for radiation planning. The plastics built into them are modeled on human tissue, so that the interaction of the radiation with these plastics corresponds to the interaction of the radiation with human tissue. Inspired by this terrestrial application, the phantoms are now also being used in space to measure the radiation affecting humans there and to be able to develop appropriate protective measures based on this.

The phantoms consist of different epoxy resins filled with additives. This allows the different densities of organs, bones and tissues to be simulated. The plastic in the phantom must exactly match the density of the real lung in the human body at the location of the lung.

Dr. Berger explained to us exactly how the phantoms are constructed:

There is a total of 1,400 such measuring points per phantom. These are equipped with small passive radiation detectors consisting of crystals. The sensors of the active detectors are also integrated at the most radiation-sensitive points of the female body: Lungs, stomach, uterus and bone marrow. The detectors make it possible to generate a three-dimensional image of the radiation distribution in the (female) body or phantom. This makes it possible for the first time to measure what radiation affects female and male astronauts during a flight to the moon – and to do so with great accuracy.

The two 95-centimeter-tall phantoms are named Helga and Zohar. They are virtually twins – with a single but crucial difference: Zohar will wear the newly developed radiation protection vest "AstroRad" from the Israeli partner StemRad during the flight. Helga will fly without a protective vest. Her data will be used to determine the effectiveness of the new radiation protection vest.

Here, too, plastic plays a supporting – and protective – role: "The vest is composed of a proprietary plastic with differential thickness around the body to complement the body's own self-shielding and provide selective protection of the most radiation sensitive organs and regions with high stem cell concentrations. This approach provides the greatest biological impact of protection with the least amount of mass, an important consideration for any object being launched into space," Dr. Oren Milstein, CEO and Chief Scientific Officer of StemRad, reveals to us in an interview. "Functionally, individual solid shielding elements are organized into a scale-like hexagonal architecture to allow for uninhibited, comfortable movement of the astronauts while wearing the AstroRad."

Low weight and high wearing comfort – we already know these properties of plastic from our sportswear. But it is also particularly suitable for radiation protection.

In total, the Artemis 1 mission lasts up to 42 days. The Orion spacecraft flies around the moon several times and then returns to Earth. Afterwards, the project team around Dr. Berger receives the two phantoms back, can read out the various detectors and start evaluating the data. In this way, plastics can make a valuable contribution to radiation protection in space in two ways.