Extravehicular Mobility Unit (EMU) Batteries: A Deep Dive into Spacewalk Power Sources

The Extravehicular Mobility Unit (EMU), also known as the spacesuit, is a critical piece of equipment used by astronauts during spacewalks (ExtraVehicular Activities, or EVAs). These suits are designed to provide a sealed, pressurized environment for astronauts to perform critical tasks outside the International Space Station (ISS) or other spacecraft. Central to the operation of these suits are the batteries, which must be capable of withstanding the harsh conditions of space.

The Primary Battery: Nickel-Hydrogen Batteries

The primary type of battery used in spacesuits, particularly the EMUs, is the nickel-hydrogen (NiH2) battery. Nickel-hydrogen batteries are favored for their reliability, long lifespan, and ability to withstand the extreme conditions of space. These batteries are capable of providing power for various essential systems in the suit, including life support, communications, and thermal regulation.

Secondary Power Solutions: Lithium-Ion Batteries

In addition to NiH2 batteries, spacesuits may incorporate smaller lithium-ion (Li-ion) batteries for specific functions or as a backup power source. This is due to the higher energy density and lighter weight of lithium-ion batteries compared to nickel-hydrogen batteries. For example, the LLB (Long Life Battery) contained within the EMU is an excellent illustration of this integration.

LLB Long Life Battery: A Detailed Examination

The LLB is a lithium-ion battery with a capacity of 26.5 Amp hours and an output voltage between 16-20 volts. This battery is strategically placed near the bottom of the backpack component of the EMU. It consists of 80 18650 lithium-ion cells, arranged in five serial banks of sixteen parallel cells. This configuration ensures a stable and efficient power supply for the suit's operation.

The Importance of Battery Technology in Spacesuits

The choice of battery technology in spacesuits is critical for maintaining astronaut safety and ensuring the successful completion of EVAs. The combination of NiH2 batteries and Li-ion batteries in the EMU demonstrates a pragmatic approach to meeting the diverse power requirements of extravehicular activities. The NiH2 batteries provide the reliability and long lifespan necessary in the harsh space environment, while the Li-ion batteries offer the energy density and weight savings required for various specific tasks.

Conclusion: Balancing Reliability and Efficiency

Spacewalks, or EVAs, are essential for the maintenance, repair, and construction of space stations. The power source choices in the Extravehicular Mobility Unit (EMU) reflect careful consideration of both reliability and efficiency. While nickel-hydrogen batteries ensure the longevity and safety of the astronaut, lithium-ion batteries offer the necessary power for specific tasks without compromising the overall weight and stability of the suit.

The integration of these battery technologies in the EMU represents a significant advancement in spacewalk technology, enabling astronauts to perform their crucial work in the challenging environment of space.