Can an Artificial Geomagnetic Field Protect Mars Colonists from Cosmic Rays?!
Shawn Wasserman posted on December 06, 2017 | 1276 views

The dream of colonizing Mars has been rattling around the public conscious for a very long time. Unfortunately, Mars’ lack of a geometric magnetic field shielding colonists from cosmic rays will ensure a radiation dose that can end a career after a single mission window.

Simulation of a magnetostatics field that could shield colonists on Mars from cosmic rays. Image features a crater wall and floor (brown line), primary shielding cables (red line), return currents on the east crater wall (blue line) and return currents off the crater wall (purple line). Areas in white are shielded below human safety limits. The colored area at the floor of the crater would house the habitat. (Image courtesy of Lake Matthew.)
Simulation of a magnetostatics field that could shield colonists on Mars from cosmic rays. Image features a crater wall and floor (brown line), primary shielding cables (red line), return currents on the east crater wall (blue line) and return currents off the crater wall (purple line). Areas in white are shielded below human safety limits. The colored area at the floor of the crater would house the habitat. (Image courtesy of Lake Matthew.)

However, our drive to boldly go where no one has gone before has led us to many discoveries both in space, with Hall thrusters, and on the ground, with tricorder-like cell phones. Could Star Trek also be hiding the key to Mars’ cosmic ray problem?

It seems that real life can’t stop mimicking Roddenberry’s science fiction utopia as Lake Matthew Team, an award-winning team from HP’s MARS Home Planet contest, has simulated a concept particle deflector shield for Mars colony habitats. The HP award was presented at this year’s Autodesk University and was sponsored by both Autodesk and NVIDIA. The project challenges teams to design a Mars habitat that could protect a million people as they live, work and travel the planet.

Designing a Mars Colony Magnetostatics Cosmic Ray Shield

This artificial geomagnetic field is created using magnetostatics, but for all intents and purposes, it acts just like the deflector dish on the old USS Enterprise. It creates a field of energy that deflects dangerous particles around the colony.

Lake Matthew’s simulation assumes that its shield will be protecting Mars’ Omaha Crater, which is 9km (5.6 miles) in diameter and 2km (1.2 miles) deep. For a crater this size, the team discovered that the power requirement for the shield was 80kW (107 hp), or about the same as a small car.

Omaha Crater pictured with crew facilities along the north/south centerline. Shielding near the east and west rims of the crater istoo weak for human safety. (Image courtesy of Lake Matthews.)
Omaha Crater pictured with crew facilities along the north/south centerline. Shielding near the east and west rims of the crater is too weak for human safety. (Image courtesy of Lake Matthews.)

Traditional Mars enthusiasts have suggested that colonists could shield themselves from radiation by burying their habitats a dozen or so feet under ground or find a frozen tunnel or cave to house the lab.Even the Lake Matthew Team has suggested creating an artificial lake on top of its habitat. However, none of these plans would protect the colonists when they are outside of the habitat.

Theoretically, a magnetostatics field could protect the colonists and could be scaled to protect larger habitats. Perhaps even mobile transports and equipment could one day see this type of protection, allowing for missions well out of range of the habitat’s protection.

You might be wondering, why not design the shield using electrostatics? Well Lake Matthew notes that this wouldn’t work in a Martian atmosphere. As the team wrote, “The atmosphere’s electrical conductivity is far too high to permit the buildup of useful electrostatic shield potential. It’s roughly two orders of magnitude higher than Earth’s atmospheric conductivity… On Mars, an electrostatic shield would suffer continual electrical discharge, which prevents operation.”

In comparison, Lake Matthew reports that the magnetostatics shield could potentially “deflect all solar storm protons, nearly all solar flare protons and more than one-half of galactic cosmic ray (GCR) protons. The design applies existing technology from superconducting power lines, superconducting solenoids and carbon nanotube cables.”

Shield-generating cables (left) and a suggested powerline cabling layout. (Image courtesy of Lake Matthew.)
Shield-generating cables (left) and a suggested powerline cabling layout. (Image courtesy of Lake Matthew.)

The deflector shield is created using five high-temperature superconductor unipolar power lines running a combined current of 24.8 MA. So, it’s not quite a Star Trek deflector dish yet. These primary shielding cables are spaced out at a distance of 1.25km (0.78 miles) and are 500m (1640 ft) above the preimpact surface. The central cable is a bundle of 100-kA conductors that max out at 6.4 MA of DC current. Current is returned to the primary cables using lines that are suspended 1km (0.62 miles) above the crater’s floor.

“Modeling indicates that the shield is effective against protons to 1 GeV,” added the Lake Matthew Team. “Shield effectiveness decreases by roughly 100 MeV for each 100-m (328-ft) decrease in vertical separation of shielding cables.”

All of these cables are then grounded and suspended via nickel/iron pylons affixed to the rim and wall of the crater. They are also refrigerated using almost 100km (62 miles) of refrigeration cables.

“Terrestrial refrigeration requirement is roughly 1 W/m,” joked Lake Matthew.“The extremely cold Martian environment eases refrigeration requirement (one easy thing on Mars), so the power requirement might be somewhere between 30 and 80 kW.”

Simulation Results of the Mars Colony Cosmic Ray Deflector

Lake Matthew used 3D magnetostatic finite element modeling with charged particle tracking to simulate its design. Since about 90 percent of the ionizing cosmic rays are protons, the simulation focuses on particles of this nature.

The simulation assumes that the protons are heading towards the shield vertically, as these would be the hardest to deflect since they have the briefest residence time within the shield. However, to validate this assumption, simulations were conducted that verified that protons hitting the shield at low angles were easily deflected.

Simulations were presented both in overhead and perspective view to assess the shielding of 500-MeV and 1-GeV protons injected vertically on the shield. The results show that nearly all of the 500-MeV protons and more than half of the 1-GeV protons were deflected.

Comparison of an overhead view of the shielding effect for 500-MeV protons (top) and 1-GeV protons (bottom). The protons (white lines) are tracking vertically, and the crater is indicated by the red line (top image only). Results show that nearly all 500-MeV protons are deflected, while more than half of 1-GeV protons are deflected in the simulations, respectively.

Comparison of a perspective view of the shielding effect for 500-MeV protons (top) and 1-GeV protons (bottom). The protons (black lines) are tracking vertically, and the crater is indicated by the red line (top image only). Results show that nearly all 500-MeV protons are deflected, while more than half of 1-GeV protons are deflected in the simulations, respectively.

As previously mentioned, these results translate into the deflection of nearly all solar flare protons and over half of GCR protons. As a point of comparison, Lake Matthew declares that this artificial geomagnetic field would actually exceed the performance of the Earth’s natural geomagnetic field. Fascinating!

So, will a deflector dish like technology be used to shield a Mars colony? These results look very promising, but they are not ready for deep space yet. As Lake Matthew writes, “This is all still first pass. It needs magnetohydrodynamic modeling for completeness, but the preliminary results have survived initial expert review.”

Let’s hope that these tests will one day prove positive so that Mars colonists can live long and prosper.

For more on Lake Matthew’s project, its references and more, follow this link.

For more on the HP’s MARS Home Planet award, presented at Autodesk University, follow this link.

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