Power systems are a critical part of a spacecraft. They need to be able to operate in extreme environments and be utterly reliable. Yet, with the ever-increasing power demands of more complex spacecraft, what does the future hold for their power technologies?

The latest mobile phones can barely last a day without the need to be plugged into a power socket. Yet the Voyager space probe, which was launched 38 years ago, is still sending us information from beyond the edges of our solar system. The Voyager probes are capable of efficiently processing 81,000 instructions every second, but the average smartphone is more than 7,000 times faster.

Your mobile phone is, of course, designed for regular recharging, and is unlikely to ever be several million miles from the nearest socket. Recharging a spacecraft, when it is 100 million miles from the nearest charging point, is impractical. Instead, a spacecraft must be able to either store or generate sufficient power to keep going for decades in space. That, it turns out, can be quite a difficult thing to achieve.

While some onboard systems only require power occasionally, others need to be continually operational. Transponders and receivers need to be active all the time, as well as life-support and lighting in the case of a manned space flight or space stations.