Fly me to the moon: how plastics contribute to radiation protection in space
Fly me to the moon: how plastics contribute to radiation protection in space
In the MARE experiment, plastic phantoms are to provide information about the risks of space radiation for humans
Exclusively for K-MAG
The crew of the Artemis-1 mission to the moon. Copyright: German Aerospace Center (DLR)
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.
Plastics on mission in space
However, plastics also play a crucial role in radiation protection. Radiation in space poses a high health risk for astronauts, especially during long-term stays.
This is also the subject of the MARE experiment (Matroshka AstroRad Radiation Experiment). This is being conducted by the German Aerospace Center (DLR) together with other partners – including NASA and the Israel Space Agency.
The MARE experiment is taking place as part of NASA's Artemis 1 mission. This involves an unmanned flight of the U.S. Orion spacecraft. The spacecraft is to enter a high lunar orbit, orbit the moon several times and return to Earth. The mission is expected to provide important knowledge for the first manned flight. This is currently planned as Artemis 2 for May 2024.
Dr. Thomas Berger explained to us what the experiment is about and what plastics have to do with it. He is a radiation expert and head of the Biophysics working group at DLR's Institute of Aerospace Medicine:
Phantom made of plastic. Copyright: German Aerospace Center (DLR)
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.
Layer by layer: construction of the phantoms
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.
Helga in individual parts. Copyright: German Aerospace Center (DLR)
Helga's superstructure. Copyright: German Aerospace Center (DLR)
By 2020, 566 people worldwide had been sent into space – only 65 of them were women. So far, not a single one has been to the moon. That should and will change in the future. But previous experiments on space radiation have focused mainly on men. Yet women are at greater risk due to their higher incidence of breast and lung cancer. DLR therefore deliberately chose female phantoms for the MARE experiment.
Newly developed radiation protection vest "AstroRad" Zohar will be equipped with during the experiment. Copyright: StemRad
Comfortable radiation protection thanks to plastic
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.
AstroRad ProtectiveCore. Copyright: StemRad
Milstein explains why this is so: "When high energy cosmic rays, consisting mainly of protons and other positively charged particles, collide with a shielding material, they are slowed down and ultimately stopped by the interactions with the material’s electrons. As a result, a good space radiation shielding material must have a high concentration of electrons. Hydrogen is the most efficient material for shielding against radiation because it has almost double the number of electrons per unit mass as any other element. High-density hydrocarbon polymers, such as plastic, are the perfect combination of lightweight solid materials with a large composition of hydrogen."
This is what it looks like when layer by layer the phantom Zohar is built:
To the moon and back again
So where do we go from here? Dr. Berger is confident:
Helga and Zohar are ready for transport. Copyright: German Aerospace Center (DLR)
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.
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