The intensity of space radiation is much greater outside Earth's protective magnetic field. This causes problems for the human body and represents a challenge for future crewed space missions to the Moon and Mars. The German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) is conducting research to determine the radiation risk for crewed spaceflight. One of the projects that the researchers are carrying out together with NASA, the Israeli Space Agency ISA and the companies Lockheed Martin and StemRad is the Matroshka AstroRad Radiation Experiment (MARE).
In the autumn of 2019, the Principal Investigator (PI) of the MARE project, Thomas Berger from the DLR Institute of Aerospace Medicine, travelled to NASA's Johnson Space Center in Houston, Texas for the fit check. The Orion technicians rehearsed the installation procedure within the spacecraft using two replicas identical in size and weight to the phantoms Helga and Zohar, which will fly to the Moon. "First of all, they had to test whether they would be able to carry Helga and Zohar in their transport frame through the hatch and into the Orion capsule. Each phantom weighs 50 kilograms, although the weight of Zohar's AstroRad vest increases this to 76 kilograms. The installation required three or four NASA technicians," explains Berger, a DLR scientist who heads the Radiation Biology Department. "Orion's command capsule is narrow, but it worked well, and the frame, with which the measuring bodies are connected with the spacecraft, also fitted perfectly. Twelve fixing screws were used to anchor the 'passenger seats' firmly to the spacecraft."
The MARE project continues to gain momentum
The fit check in the Orion spacecraft was successful. The vibration tests carried out at the DLR Institute of Space Systems in Bremen, which tested the resilience of the connection between the phantoms and their 'seats' also confirmed the quality for the construction. The Israeli AstroRad radiation protection vest recently arrived at the DLR Institute of Aerospace Medicine in Cologne. The next big step for the MARE team will come in January. "That is when we will receive a visit from our industrial partner, StemRad, who developed the AstroRad vest. Together we will take a close look at the vest and at Zohar, who is going to wear it during the flight to the Moon. If necessary, we will adjust the vest again to achieve an optimal fit. We will then integrate our own sensors and those developed by our partners and co-investigators into Zohar and Helga. NASA is currently planning Orion’s flight to the Moon for autumn 2020, so MARE is on track."
The new generation of DLR Matroshka experiments are female
The Matroshka experiments are examples of phantoms, measurement bodies modelled on the human torso. DLR already has a great deal of experience with these devices. The last time a Matroshka was used was by DLR's aerospace medicine researchers in Cologne. It was installed on the International Space Station (ISS) between 2004 and 2011. Mounted on the outside of the ISS, the phantom collected radiation readings as if it were an astronaut carrying out a spacewalk. The phantom also spent time in the Russian and Japanese parts of the ISS to measure radiation levels at those locations.
The new generation of Matroshkas is modelled on female physiology for the first time. As the number of female astronauts increases, there is an increasing need for data on the effects of prolonged space travel on the female body. The female body is typically more vulnerable to radiation and so different safety parameters apply to female astronauts than to their male counterparts. However, so far there have been no gender-specific studies using measurement bodies in space.
During the flight, Zohar will wear a protective vest, while Helga will be without one. The identical models will gather comparable data sets from beyond low Earth orbit for the first time. A total of over 6000 active and passive sensors are attached to the bodies' exterior and fitted to their interior. The bodies consist of plastics of different densities to simulate the human skeleton and organs at anatomically appropriate positions within the body. After the flight to the Moon, the radiation values measured by both Matroshkas will be compared in order to evaluate the efficacy of the AstroRad protective vest and improve it in future, if necessary.
The Orion Artemis I mission and DLR
NASA's goal for the Artemis I mission is to conduct a first unmanned flight of Orion to the Moon, enter orbit and then return to Earth. The duration of the flight will be between 26 and 42 days. The MARE experiment is on board as a secondary or scientific payload. This means that both Matroshka phantoms have to work independently of the spacecraft. From power supply to data storage, all functions are completely independent of Orion itself.
DLR is project lead for MARE, is providing the phantoms and will make all of the necessary adjustments for the experiment and the spaceflight in the Orion capsule. In addition, DLR researchers are constructing the attachment systems for the two phantoms and are responsible for evaluating the data after the landing. MARE is the largest experiment for determining the radiation exposure of astronauts that has ever left near-Earth orbit. It is an international cooperation between numerous universities and research institutions in Austria, Belgium, Poland, Hungary, the Czech Republic, Greece, Switzerland, Japan and the USA. It will provide fundamental data for estimating the radiation risk for future crewed flights to the Moon.