interview
As of: 03/09/2023 3:52 p.m
Two dolls flew into space and back in a spaceship as part of a radiation experiment. Thomas Berger from the German Aerospace Center explains why the Artemis I mission is important for the future of manned spaceflight.
tagesschau.de: In December, the two measuring dummies landed safely on earth again with the “Orion” space capsule. How happy were you?
Thomas Berger: Very happy. The two puppets, which we scientists have named “Helga” and “Zohar”, have traveled more than two million kilometers in space after around 25 days. Orion is a human-rated spacecraft, a human-built spacecraft that has traveled farther from Earth than any such spacecraft has ever been. After landing in the Pacific, Orion was shipped back to NASA, Kennedy Space Center, in Florida. Then “Helga” and “Zohar” were removed from the spaceship by our NASA colleagues and arrived safely at DLR in Cologne two weeks ago.
To person
dr Thomas Berger is head of the “Biophysics” working group at the German Aerospace Center in Cologne. His research focuses on radiation protection and the development of radiation detectors.
tagesschau.de: Thousands of detectors were installed in the two dummies. They measured how much radiation affects the dolls in space. How did this work?
Berger: The dolls are made up of 38 discs of plastic of varying density, simulating the various organs of the human body. We measure the radiation with active and passive detectors: The active measuring devices are battery-operated. They save the radiation dose measured at a specific point in time, which is every five minutes for our detectors. This means that after evaluating the measurement data, we can say how high the radiation dose was in free space at a certain point in time, for example when Orion flew past the moon. The active detectors thus provide a time-resolved distribution of the radiation over the entire mission. That is the advantage of these measuring devices.
Image: Ute Spangenberg/SWR
tagesschau.de: At which points on the dolls did the detectors measure the radiation?
Berger: Several active measuring devices were installed in the lungs, stomach, uterus and spinal cord. These are the most radiation-sensitive organs in the human body, so after the evaluation we can say, for example, how high the radiation dose was in the lungs on the fifth day of the mission.
6000 detectors in each doll
tagesschau.de: And what was the task of the passive detectors?
Berger: We have installed around 6,000 passive detectors – these are small crystals – in each phantom, making a total of 12,000 pieces. 80 percent came from DLR, 20 percent from NASA. The whole spaceship was equipped with detectors like a Christmas tree. The crystals are called thermoluminescence detectors. Basically, they store the ionizing radiation that hit them in space in their crystal lattices. If we now heat them for the evaluation, they emit the stored energy in the form of light and this light can be measured. The light emitted by the crystals is proportional to the radiation dose they have absorbed over the time of the experiment. With these crystals, we can map the total dose over the mission and ultimately obtain a three-dimensional radiation distribution.
tagesschau.de: What are these crystals made of?
Berger: The crystals are made of lithium fluoride. These detectors have been used in radiation protection for ages. For example, if you work at a nuclear power plant or in radiology at a hospital, you also wear dosimeters that measure your radiation dose. Among other things, these crystals are also installed in it.
Test dummies have female bodies
tagesschau.de: The dummies they developed are women’s bodies. Why?
Berger: On the one hand, there are now more female astronauts, which is absolutely to be endorsed. But unfortunately it is also the case that the general radiation-induced cancer risk is higher for women than for men. The overall cancer risk of the body is made up of cancer risks of the organs, and in women there is an additional proportion of breast cancer. And because of this, the overall risk is greater for women than for men. There’s not a lot of basic metrics out there for the female body yet, so we flew these two female bodies.
Image: Ute Spangenberg/SWR
tagesschau.de: One of the two dolls wore a radiation protection vest during the flight. What insights are you hoping for?
Berger: The Zohar doll, funded by the Israel Space Agency (ISA), wore a 26-kilogram vest, the AstoRad Vest, developed by Israeli company StemRad and made of high-density polyethylene. The basic idea of this vest is that it should give astronauts additional radiation protection, especially during a solar flare, when they fly in space – as part of the Orion mission or also on future exploration missions to Mars. Last week, for example, you could see the northern lights in northern Germany. This is a clear sign that charged particles were being emitted from the sun, which then created the aurora by interacting with the molecules in the atmosphere. Then you see the beautiful lights. But at the same time, these particles emitted by the sun pose a high risk: astronauts could get radiation sickness. In order to be able to additionally shield this radiation dose, this vest was developed. Since only one of the two dolls wore this armor vest, we can see what the vest really does.
Analysis of results in progress
tagesschau.de: When do you expect the results of your evaluations? Finally, in 2024, Artemis II is said to have humans on board the Orion spacecraft.
Berger: We read the active detectors at the Kennedy Space Center in January immediately after the handover, i.e. we saved the data for posterity and science, so to speak. We are currently working on the analysis. The evaluation of the passive detectors, which were mainly made available by DLR, will certainly keep us busy for the next six months to a year.