Orion spacecraft radiation protection tested: initial findings from Artemis I Moon mission
NASA
- Artemis I mission measurements: during the Artemis I mission, the Helga and Zohar mannequins continuously recorded radiation data between the Earth and Moon for the first time, in order to analyse the radiation conditions inside the Orion capsule and assess its suitability for future space missions.
- Health risks from space radiation: space radiation can cause cancer and degenerative diseases during long-term space missions, which is why suitable protective measures are required to protect astronauts.
- Focus: Spaceflight, protection from space radiation
During long-term astronaut missions, space radiation poses health risks to the human body. Such radiation can lead to cancer and several degenerative organ diseases, so suitable protective measures need to be found to ensure that astronauts are protected to the greatest extent possible during ever longer space missions in the future. For this, researchers need detailed measurement data on radiation exposure during spaceflight beyond the Earth's magnetic field. In late 2022, the measurement dummies Helga and Zohar were launched aboard NASA's Orion spacecraft as part of the MARE project led by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR), alongside numerous radiation sensors. As part of the Artemis I mission, they flew to the Moon and back on a journey spanning over 25 days. For the first time, continuous measurement data on the radiation levels between Earth and its natural satellite, almost 500,000 kilometres away, were obtained. The research team from DLR, the European Space Agency (ESA) and NASA have now published their initial findings in the scientific journal Nature.
Thomas Berger, radiation physicist at the DLR Institute of Aerospace Medicine in Cologne and the Principal Investigator of the MARE experiment, explains: "We had two main objectives for the Artemis I mission. For the first time, we wanted to collect a comprehensive and coherent data set on the radiation conditions during a lunar flight, and we are still analysing this data. And, together with NASA and ESA, we wanted to characterise the variations in radiation exposure inside the Orion spacecraft, for which the results are now available. To do this, we placed numerous radiation detectors, known as dosimeters, at various fixed positions within the spacecraft and inside our two life-size MARE measuring mannequins, Helga and Zohar," explains Berger. The MARE experiment is a joint project between DLR, the Israeli company StemRad, NASA, Lockheed Martin and the Israeli Space Agency (ISA).
Significant differences in radiation exposure within the Orion spacecraft
The measurement results have now been published in the scientific journal Nature. They show that during the flight through Earth's proton belt – the inner Van Allen belt – the radiation exposure within the spacecraft differed very significantly depending on the location of the detector. The dose rates between the most and least protected areas within the space capsule differed by a factor of four. These enormous differences validate the design and shielding concept of the space capsule. In the more heavily shielded area of the capsule (Storm Shelter), the total dose of radiation from large solar particle events can be limited to a maximum of 150 millisieverts. At this dose, no signs of acute radiation sickness are expected.
Suitability of the Orion capsule for human spaceflight
The data also show that the orientation of the spacecraft during the flight through the proton belt had a significant effect on the radiation levels inside the capsule. At the end of the flyby through the inner Van Allen belt, Orion performed a 90-degree turn, which led to an unexpectedly large reduction in the radiation dose of 50 percent. "This shows us that this flight manoeuvre can significantly reduce the radiation exposure for the crew. This is also a good sign and confirms the basic suitability of Orion for future spaceflight with astronauts. Our measurement data also provides a solid knowledge base for the design of future missions," emphasises Berger.
Last but not least, the recently published study shows an improvement in modern computer simulations of radiation environments, as the experimental measurement data largely match the predicted model calculations. This is also an important factor for the efficient, time- and cost-effective further development of the Orion concept.
Overall, the scientific team concluded in the Nature publication that the radiation exposure for future Artemis missions, with durations ranging between a few days and weeks, is unlikely to exceed NASA's current limits for astronauts, assuming similar mission conditions are maintained. However, radiation risk remains one of the key challenges for human spaceflight.
Together with NASA and ESA – measuring radiation to effectively protect future Orion crews
Artemis I was the first in a series of missions under NASA's Artemis programme. The aim is to send humans back to our satellite after more than 50 years, establish a permanent base there together with international partners and build a space station in lunar orbit from which humans will set off for more distant destinations, including Mars. On 16 November 2022, the NASA Artemis I Moon mission launched from the Kennedy Space Center in Florida. During this as yet uncrewed mission, all newly developed systems were tested in combination – the Orion spacecraft, the European Service Module (ESM), the Space Launch System (SLS) heavy-lift rocket and the ground systems.
NASA equipped the Orion spacecraft with its radiation measurement and warning system – the Hybrid Electronic Radiation Assessor (HERA). HERA consists of three radiation sensors installed in areas of Orion that are shielded from radiation to varying degrees. It is designed to trigger an alarm if the crew needs to seek shelter due to a high-energy radiation event, such as a solar flare. In this case, the astronauts would move to a more shielded part of Orion, opening the floor hatches and then installing shielding material over their heads as additional protection.
ESA provided five mobile dosimeters – the EAD-MUs (ESA Active Dosimeter – Mobile Units) – placed at various locations in the space capsule to measure the radiation. A predecessor system of the mobile units was used on the International Space Station ISS from 2016 to 2017. Orbiting the Moon during the Artemis I mission allowed for the most comprehensive possible mapping of the radiation environment in deep space. The new values are now being compared with the ISS measurements to assess the safety of subsequent crewed Artemis missions. A refined version of the EAD-MU system will be used on board the Lunar Gateway – a planned space station in lunar orbit.
The ESA dosimeters distributed in the Orion capsule were designed, tested and built by the DLR Institute of Aerospace Medicine together with ASRO in Finland. The active DLR M-42 measuring devices and passive sensors in Helga and Zohar were also developed and manufactured by DLR's Institute of Aerospace Medicine.
"The detectors measure different types of radiation, enabling us to use the values to draw conclusions about their biological effects," says Berger. The two measuring mannequins in the MARE project were specially designed to mimic female anatomy to investigate the particular effects of radiation on women in long-duration space missions.
The results published in Nature are the first in a series. Researchers from DLR, NASA and ESA are continuing to analyse the extensive radiation data measurements from the Orion flight. Thomas Berger and the DLR MARE project team are currently working on comparing the radiation exposure of Helga, the measurement mannequin that flew unprotected, and Zohar, who wore the AstroRad radiation protective vest while flying around the Moon.
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Measuring space radiation – from 'patchwork quilt' to a consistent data set
Space radiation comes from various sources such as solar particle events, galactic cosmic rays or the two Van Allen belts around Earth which are very radiation intensive. Earlier radiation data was acquired mainly from the International Space Station ISS and space shuttle missions – and therefore from relatively low altitudes which are still protected by Earth's magnetic field. Data from the depths of interplanetary space was obtained during various uncrewed missions in which probes travelled through the Solar System, for example to Mars. There is also limited data from the Apollo missions to the Moon.
Continuous radiation measurements with a high spatial resolution have not yet been taken but were first carried out during the Artemis I mission that travelled between Earth and the Moon.
About the DLR MARE experiment
DLR is leading the Matroshka AstroRad Radiation Experiment (MARE). The main project partners are the Israeli space agency ISA, the Israeli industrial partner StemRad – who developed the AstroRad protective vest, as well as Lockheed Martin and NASA. In terms of its complexity and its international collaboration with numerous universities and research institutions from Europe, Japan and the USA, MARE is the largest experiment to determine the radiation exposure to astronauts that has left low-Earth orbit. The measurements carried out during the Artemis I mission will provide valuable data for assessing and reducing the risks associated with future long-term missions to enable safe human space exploration.