Artemis I Demonstrated Adequate Radiation Shielding for Manned Lunar Missions

Guest “We already knew this from the Apollo Program” by David Middleton

NASA’s “crash test dummies” Helga and Zohar, along with an array of radiation instrumentation demonstrated that the Artemis spacecraft provides adequate shielding for short duration lunar missions. The results of these measurements were recently published in Nature.

a, Radiation instrumentation and phantoms inside Orion. These consist of the NASA HERA system, the ESA EAD system, as well as the NASA CAD and DLR M-42 instruments. The HERA system and the EADs were hard-mounted at various distinctly shielded locations in Orion. CAD and M-42 were placed on the front and back surfaces (skin) and inside (organs) (M-42) of the MARE phantoms (Extended Data Figs. 1–4). b, Placement of the instrumentation and hardware inside the Orion spacecraft. c, The Orion flight profile with respect to radiation for the NASA Artemis I mission. After launch at 06:47 UTC on 16 November 2022, Orion passed the inner (proton-dominated) and outer (electron-dominated) Earth radiation belts. Orion then ventured into interplanetary space dominated by GCRs. It passed the Moon twice on 21 November (first lunar fly-by at a distance of 130 km) and on 5 December (second lunar fly-by at a distance of 128 km). During these fly-bys, the Moon acts as a shield against GCRs. Orion re-entered Earth’s atmosphere over the South Pole and landed in the Pacific Ocean close to San Diego, California on 11 December 2022 at 17:40 UTC. Nature ISSN 1476-4687

The paper is open access, with the full text freely available. Here’s the abstract:

Abstract

Space radiation is a notable hazard for long-duration human spaceflight¹. Associated risks include cancer, cataracts, degenerative diseases² and tissue reactions from large, acute exposures³. Space radiation originates from diverse sources, including galactic cosmic rays⁴, trapped-particle (Van Allen) belts⁵ and solar-particle events⁶. Previous radiation data are from the International Space Station and the Space Shuttle in low-Earth orbit protected by heavy shielding and Earth’s magnetic field^7,8 and lightly shielded interplanetary robotic probes such as Mars Science Laboratory and Lunar Reconnaissance Orbiter^9,10. Limited data from the Apollo missions^11,12,13 and ground measurements with substantial caveats are also available¹⁴. Here we report radiation measurements from the heavily shielded Orion spacecraft on the uncrewed Artemis I lunar mission. At differing shielding locations inside the vehicle, a fourfold difference in dose rates was observed during proton-belt passes that are similar to large, reference solar-particle events. Interplanetary cosmic-ray dose equivalent rates in Orion were as much as 60% lower than previous observations⁹. Furthermore, a change in orientation of the spacecraft during the proton-belt transit resulted in a reduction of radiation dose rates of around 50%. These measurements validate the Orion for future crewed exploration and inform future human spaceflight mission design.

George et al., 2024

Artemis II

Artemis II could launch as early as September 2025. The 10-day mission to orbit the Moon will be the first manned mission to the Moon since Apollo 17 in December 1972.