With the acceleration of missions such as deep space exploration, satellite maintenance, and moon base construction, the space robotics market size continues to grow. According to Grand View Research 2024 report, the scale of global investment in spaceland robotics is expected to exceed USD 22 billion by 2030, at a CAGR of 17.3%. As a core energy component, batteries need to meet the following stringent conditions: extreme temperature adaptability, ultra-high energy density, radiation resistance and long life.
Currently, mainstream solutions include nuclear energy batteries (RTGs), lithium-sulfur batteries, and solid-state batteries, but cost and reliability are still bottlenecks (NASA data shows that battery systems account for 30-40% of the total cost of a robot).
1. Battery challenges for space robots
1.1 Extreme environmental impact
The high radiation environment in space can damage the structure of battery materials, leading to changes in the crystal structure of electrode materials, increasing internal resistance and decreasing charging and discharging efficiency. According to the research of the National Aeronautics and Space Administration (NASA), the capacity of satellite batteries operating in near-Earth orbit for one year can decay up to 10%-15%. In addition, the ultra-low temperature environment will increase the viscosity of the electrolyte and slow down the ion conduction speed, which will further reduce the battery performance. In the extremely cold environment on the backside of the moon, the temperature can be as low as -180 degrees Celsius, and ordinary batteries can hardly work normally.
1.2 Diversity of mission requirements
Different space missions have different requirements for battery performance. Short-term planetary exploration robots emphasize high power output to support intense work such as sample collection and rapid movement. Long-term deep space exploration robots, on the other hand, require extremely high energy density and long lifespan to ensure continuous operation for years or even decades. For example, since its launch in 1977, the Voyager probe has continued to rely on nuclear batteries for normal operation.
2. Existing Battery Technologies in Space
2.1 Lithium ion batteries in robots
Lithium-ion batteries are widely used in space robotics because of their high energy density and relatively stable performance. For example, some experimental equipment on the International Space Station (ISS) uses lithium-ion batteries as a power source, meeting the need for lightweight and high energy storage. However, lithium-ion batteries are prone to capacity degradation and safety hazards under extreme temperature conditions, and their limited cycle life may require frequent battery replacement for long-term missions, increasing the complexity and cost of operations.
2.2 Nickel-metal hydride batteries
Nickel-metal hydride (Ni-MH) batteries have good low-temperature performance and were widely used in early space missions. They have high charge/discharge efficiency and good safety, but their low energy density means that a larger and heavier battery is required to meet the same energy demand. This poses a challenge for space missions with stringent weight requirements, and the use of NiMH batteries has gradually been limited as energy demand rises.
3.New Battery Technology Solutions
3.1 Solid State Batteries
Solid-state batteries, as an emerging technology, show the potential to become an ideal choice for robot battery spaceland. It uses a solid-state electrolyte to replace the traditional liquid electrolyte, dramatically improving safety and reducing the risks associated with electrolyte leakage. With energy densities 30-50 percent higher than traditional lithium-ion batteries, solid-state batteries are able to store more energy in a smaller size and weight, which is critical for achieving lighter weight designs and longer mission execution times. In addition, solid-state batteries have better performance stability than conventional batteries in high and low temperature environments, and are better able to adapt to the extreme temperature conditions of space.
3.2 Nuclear Batteries
Nuclear batteries, or radioisotope thermoelectric generators (RTGs), utilize the heat generated by the decay of radioisotopes to convert it into electricity. These batteries have extremely high energy density and long lifespans, eliminating the need for frequent recharging or replacement. For example, the Curiosity Mars rover utilizes nuclear batteries, enabling it to continue operating on Mars for many years. Nuclear batteries are unaffected by factors such as light and temperature in the space environment, providing stable and reliable power output. However, nuclear batteries have issues such as high cost and safe management of radioactive materials. The use of nuclear batteries in space missions requires stringent safety and security measures to ensure that they do not pose a hazard to the Earth’s environment and astronauts during launch, operation and retrieval.
4.The key role of battery management systems
4.1Energy Optimization
An efficient battery management system (BMS) is crucial for spaceland robot batteries. It monitors the battery status in real time, including parameters such as power, voltage, current and temperature, and optimizes the charging and discharging process through data analysis to ensure that the battery is always working in the best condition, thus improving the efficiency of energy utilization. During mission execution, the BMS is able to dynamically adjust the output power according to the demand, avoiding over-discharge or over-charging and prolonging the service life of the battery.
4.2Fault Diagnosis and Fault Tolerance
The risk of battery failure in the space environment is high, and the BMS is equipped with powerful fault diagnostic functions that can detect abnormalities such as short circuits, broken circuits, and capacity degradation in a timely manner. Once a fault is detected, the BMS can quickly switch to a backup battery module or adjust the operating mode to ensure that the basic functions of the space robot are not affected. By diagnosing and handling faults in a timely manner, the BMS significantly improves the reliability and safety of space missions.
The development of battery solutions for space robots is a complex and challenging field. Existing battery technologies have limitations in the face of extreme space environments and diverse mission requirements. However, new battery technologies, such as solid-state and nuclear batteries, show great potential. In addition, efficient battery management systems play an indispensable role in optimizing battery performance, ensuring safety and improving mission reliability.
Looking ahead, with the continuous advancement of material science, energy technology and electronics, we have reason to believe that more advanced and reliable battery solutions for space robots will emerge. This will give a strong impetus to the cause of human space exploration and help us explore the mysteries of the universe more deeply.