Could A Mound of Dust and Rock Protect Astronauts from Deadly Radiation?

Protecting the astronauts of the Artemis program is one of NASA’s highest priorities. The agency intends to have a long-term presence on the Moon, which means long-term exposure to dangerous radiation levels. As part of the development of the Artemis program, NASA also set limits to the radiation exposure that astronauts can suffer. Other hazards abound on the lunar surface, including a potential micrometeoroid strike, which could cause catastrophic damage to mission equipment or personnel. NASA built a team to design and develop a “Lunar Safe Haven” to protect from these hazards. Their working paper was released in 2022 but still stands as NASA’s best approach to long-term living on the lunar surface.

The two hazards mentioned above provided the primary impetus for the design, but there are some nuances to them—in particular, radiation. Astronauts will experience two main types of hazardous radiation on the lunar surface: cosmic rays and solar eruptions. 

Cosmic rays are the more insidious of the two. They have a high energy range, so a shielding material that might work well for higher-energy particles might not do so for lower-energy ones. Moreover, some high-energy particles can interact with shielding, causing even more damaging radiation further down its path. Essentially, this increases the radiation risk inside the shielding compared to outside. The order in which the radiative particles are dealt with is one of the critical design considerations for dealing with this dangerous phenomenon. 

Lunar regolith can be hard to deal with, as Fraser discusses with Dr. Kevin Cannon.

However, solar particle events (SPEs) are the more overtly dangerous of the two types of radiation. While rare, they can cause acute radiation sickness. Current astronauts must shelter in place inside a protected chamber on the ISS when these happen, and building something equivalent on the surface of the Moon is a necessity to ensure that astronauts don’t simply die of acute radiation poisoning within the first six months of arrival.

With the problems to solve firmly in hand, the design team moved on to other considerations—like what the habitat inside the LSH would actually look like and how it would be built. Consideration of the habitat shape focused on one primary distinction—should the habitat be horizontal or vertical? The answer is vertical based on modeling the risk of radiation and micrometeoroid strikes.

So, how do you build a structure around a vertical habitat on the Moon? You employ robots and remotely operated construction equipment. Other groups at NASA had been working on solutions like the Lightweight Surface Manipulation System (LSMS), essentially a large crane that can be constructed in lunar gravity, and the Lunar Attachment Node for Construction and Excavation (LANCE) – a bulldozer module designed to attach to the front of NASA’s Chariot exploration vehicle. Utilizing these ideas and other construction ideas, it’s possible to construct a protective dome of lunar regolith around a long-term habitat for the Artemis missions. 

Fraser overviews the Artemis mission that LSH will attempt to help.

Such a protective habitat has significant advantages over digging one into the ground, which requires moving a massive amount of regolith or utilizing lava tubes with indeterminate structural integrity. But that means the LSH must have an above-ground design. The team developed two separate design ideas – a parabolic arch and a “Round Cake” design using polyethylene. The first is self-explanatory, but the second looks more like a typical cylinder with the radiation and micrometeoroid-blocking polyethylene stored in “beans” at the top of the structure. This could be made of waste materials from the mission, such as discarded food packaging.

Each design has advantages and disadvantages, and the team didn’t pick a final one as part of the paper. However, they did come up with a five-phase development process, from preparing the site in advance to living in interconnected habitats surrounded by regolith and protective shielding. Depending on the amount of automation involved and some real luck, those development phases could take anywhere from a few years to a few decades. 

It remains to be seen if this system will be adopted as an official part of the Artemis program. But it serves a need of critical importance to humanity’s long-term existence on the Moon. If that is indeed NASA’s goal for the end of the 2030s, it would be good to consider how to start making the LSH a reality.

Learn More:
Wok et al. – Design Analysis for Lunar Safe Haven Concepts
Moses & Grande – Lunar Safe Haven Seedling Study
UT – What Could We Build With Lunar Regolith?
UT – There are Four Ways to Build with Regolith on the Moon

Lead Image:
Artist’s depiction of the Parabolic Arc LSH in cutaway.
Credit – Wok et al.

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