Electronics on a moon base must be designed to withstand high radiation levels, extreme temperature changes, and fine abrasive lunar dust. That often means using different materials and system architectures to ensure reliability.

Radiation levels on the moon are much higher than those experienced in near-earth orbit, where the Earth’s magnetic field partially protects systems. For example, the lunar surface is exposed to over 2.5 times as much radiation as the International Space Station.

Well-understood techniques are available for dealing with radiation exposure in electronic systems. “Radiation-hardened” components are made with materials specifically designed to withstand the damaging effects of ionizing radiation through techniques like shielding, specialized manufacturing processes, and redundant circuitry.

Silicon-germanium (SiGe)- based devices create electronic systems resistant to extreme radiation and temperatures. Newer materials like gallium nitride (GaN) also contribute to space exploration. Materials under development for future missions include 2-D materials like graphene, black phosphorus, and boron nitride nanosheets and germanium tin (GeSn) electronic devices.

Extreme temperature swings

The temperature survivability depends on where the system is on the moon’s surface. Equatorial temperatures range from +127 °C at noon to -173 °C at night and are survivable (Figure 1). For example, Li-ion and lithium thionyl chloride batteries can survive the freezing temperatures of lunar nights.

Hibernation helps

Operation at lunar dawn can be especially challenging. The so-called “dawn mode,” when the systems come out of hibernation, is handled by the main bus controller (MBC).

At dawn, the battery is frozen and electrically isolated. The MBC must bring the PV array online without damage and ensure stable operation. There can be power quality concerns without the battery to stabilize the main power bus. One key is cryo-electronic devices that reliably start at lunar dawn.

Initial loads are limited to resistive devices to minimize transients. Those loads also help deliver heating for the thermal recovery of the overall electronics package. The battery and other systems can be brought online as thermal energy recovery proceeds.

Some lunar locations are less temperate. The permanently shadowed regions (PSRs) at the lunar poles where water ice is thought to exist have recorded temperatures as low as -238 °C.

Cold tolerant electronics

NASA’s Cold-Tolerant Electronics and Packaging for Lunar Surface Exploration (CTE-PLuS) is developing solutions for extreme cold conditions, especially in the PSRs. The goal is to develop cryo-electronic devices and advanced materials with matched coefficients of thermal expansion (CTEs) that can eliminate the need for the “warm box” approach in conventional lunar electronic systems.

By developing cold-tolerant electronics, NASA expects to create smaller, lighter, and more energy-efficient systems. They will support more complex scientific investigations in previously inaccessible areas like the PSRs.

Dusty challenges

The lunar surface is covered with fine dust particles with sharp edges ranging from 2 μm to 30 μm. Due to the sharp edges and very small geometries, it is challenging to completely seal out the dust, which presents special challenges for electro-optic sensors, imagers, and rovers.

Due to electrostatic interactions, dust floats across the surface at altitudes from 1 m to 1 km. Multiple environmental factors cause electrostatic conditions, including plasma electrons in the solar wind, ions, and solar UV rays striking the surface. These can result in surface charges ranging from -200 V during the lunar night to +3 V during the daytime.

The lunar Debye sheath refers to a thin layer of plasma that occurs on the nighttime side. A photoelectron sheath occurs on the daytime side. Lunar dust ejection occurs at the terminator areas between the Debye and photoelectron sheaths (Figure 2). The floating dust gradually falls to the surface because of gravity.

Summary

Operating on the moon is even more challenging than a deep-space mission. Like deep space, the lunar environment experiences high radiation levels. In addition, the lunar environment experiences enormous temperature swings and challenging dust conditions not encountered in deep space.

References

AS6294/1 and AS6294/3 – PEMs and PEDs for Space, NASA
Cold-Tolerant Electronics and Packaging for Lunar Surface Exploration, NASA
Exciting Lunar Moon Base Connectivity for 2024 and Beyond, Enable-IT
NASA’s Plan for Sustained Lunar Exploration and Development, NASA
Power Hibernation for Low Cost Solar Powered Lunar Missions, NASA
Setting a new standard for electronics in space, Texas Instruments
Surviving the Temperamental Moon, The Space Resource
Topology Optimization of Compliant Mechanisms as a Design Method to Improve Hardware Performance in Lunar Dust Environment, 19th European Space Mechanisms and Tribology Symposium

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