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Artificial Magnetic Fields on a Moon Base

November 25, 2024

A Moon Base occupied by humans will need protection from galactic cosmic rays in order for astronauts to endure prolonged periods on the lunar surface.  Prolonged exposure to galactic cosmic rays, or GCRs, have been found to increase the risk of cancer, damage the central nervous system, and cause DNA damage. 1

 If attempting to block galactic cosmic rays, it would require a Moon Base to be buried in at least 2 meters of regolith (moon dust and rock) posing an undesirable and impractical construction.  Likewise, a lunar space station would need an equivalent amount of shielding in the form of thick and heavy lead or tungsten, neither of which is very practical to haul into space.  This approach can also result in harmful secondary radiation when hit by the high-energy cosmic particles. 2


A better approach to shield against GCRs is by deflecting the radiation with an artificial magnetic field constructed on the Moon Base. 3, 4

A magnetic field is typically generated by running current through a loop of wire:

Passing current through a loop of wire generates a magnetic field as shown above.  Increasing the number of wire loops or amount of current increases the strength of the magnetic field, which is greatest at the center of the loop.  To simulate Earth's magnetosphere, the field strength needs to be about 0.5 Gauss.

 

A circular conduit structure can be constructed about a Moon Base, raised on supports containing loops of cable-wire, to yield a magnetic field with similar strength as the Earth’s magnetic field.

     

An artificial magnetic field is constructed about a Moon Base to shield against GCRs.  Astronauts can walk anywhere within the magnetic field and remain protected from galactic cosmic rays.  As an alternative, the arrangement on the right deploys several small circular-conduit structures to divide up the current load.  The magnetic field lines extend several meters beyond the circular structure.  Other alternatives can further optimize magnetic field loops.  

 

A lunar base with magnetic shielding were considered in the past, but unlike the open concept shown above, closed circular structures with a magnetic shield are shown in the following artists renditions:

                             

   

For a lunar space station, a toroidal design is thought to be the ideal structure to shield against GCRs.  Since plans are already underway for the Gateway lunar space station, currently shown as non-toroidal, it can either include or possibly retrofit GCR shielding utilizing the cyclindrical geometry of the modules.  For the trip enroute, a spacecraft is protected by Earth’s magnetosphere for nearly the entire trip to the Moon, or the astronauts can use the 3-4 day window each month where the Moon is protected by the Earth’s magnetosphere.

Structural conduits are incorporated into a cylindrical lunar space station module containing loops of
wire passing current to yield a magnetic field for protecting against GCRs.

 

 

          

For EVA, the lunar terrain vehicle is equipped with apparatus to provide a protective magnetic field.  On the right, an astronaut outside the Moon Base is protected by a portable loop-conduit structure. 

 

 

1.  Unshielded exposure to radiation on humans are known to be cumulative and cannot be reversed on the ground.  If the most exposure a human can withstand is 150 days (5 months) and you take a trip to the Moon without GCR shielding for 3 months, your next trip to the Moon should only be 2 months.  After that, you should no longer visit the Moon.

2.  From The Complete Book of Spaceflight (D. Darling, Wiley & Sons, 2003): ".. unless the shelter is massive [e.g., large amounts of lead cladding] (in which case it places a heavy burden on the propulsion system), it is worse than no shielding at all, because the impact of a GCR nucleus on a [sic] shield would be to spawn secondary radiation more hazardous than the first." 

3.  From Neil Armstrong's A Life of Flight, J. Barbree (St. Martin's Press, 2014): "Neil also knew .. Mars-bound astronauts would arrive as blubbering idiots from radiation poisoning - no ship headed to Mars today could carry enough lead to protect its crew.  What's needed is a lightweight radiation protection device like a small magnetic field.  .. to develop such equipment we [need] first to explore and settle our own Earth-Moon system."

4.  From The Complete Book of Spaceflight (D. Darling, Wiley & Sons, 2003): "Since GCR cumulative doses on missions lasting more than a year may exceed the recommended maximum allowable whole-body radiation dose, mission designers are considering an alternative to the simpler shelter [using shielding] in the form of an active electromagnetic field.  This would work like a miniature version of Earth's magnetic field- by bending the trajectory of incoming charged particles away from the region to be protected."