Universe | Earth | Batteries in Space | 07th November 2022 | Virtual Wire
In this article, we are going to try and answer some of the questions related to how batteries are used in space missions and why they are so important.
How are Batteries in Space Different?
The need for Insulation due to high temperatures and radiation.
They need to last longer because it’s hard to go to another planet for replacement.
What kind of factors do you need to look into in order to avoid any kind of accidents or leakage?
The batteries should be able to handle the vibrations during the launch.
They should be able to withstand the heat and the high amount of solar radiation.
The batteries also need to be sealed for protection.
Why do we need Batteries if we have Solar Panels?
Usually, spacecraft rely on solar panels to operate but they need a battery source to trigger the opening of the panels. But not all missions can rely on solar panels. Because as you get farther from the sun, there is very less sunlight that can be used to generate the power. Additionally, a satellite orbiting Earth will not receive sunlight for half the time and thus needs another power source.
What kind of Batteries has been used in Space Missions?
For example, the International Space Station previously used nickel-hydrogen batteries but after several spacewalks performed by astronauts, it has now been upgraded to lithium-ion batteries. Another example is the Voyager 2 spacecraft which uses the heat from the decay of Plutonium-238 to generate electricity. It's using three such radioisotope thermionic generators. It has no moving parts. Furthermore, the batteries will completely discharge by 2025 and thus most of the instruments have been turned off. It has been operating since 1977. Additionally, the Curiosity Rover on Mars uses a type of RTG called a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) that powers many of its instruments. The use of radioisotopes to generate heat is considered dangerous and that's why it is encased in many layers of protection. But it lasts for a very long time.
How do these rechargeable space batteries work?
These batteries are recharged using either solar panels or Radioisotop-based power (RTG). Radioisotope thermoelectric generator or RTG uses the concept of the thermoelectric effect. In RTGs, the heat is generated using some type of radioactive material that is kept inside a protective case, and then a thermocouple is used to generate voltage. Thermocouples use two different types of conducting wires or materials to generate the temperature gradient. As we know that if a metal is heated, the heat flows away from the source and thus the whole rod gets heated. Similarly, when the two conducting wires of the thermocouple are heated, the electrons will move away from the heat source and thus get collected on the colder end. And since both materials conduct heat differently, a temperature gradient is developed. And that’s what we need to generate a voltage. Missions that are farther from the sun don’t get enough sunlight to be able to charge the battery and thus RTG is used.