2015 – Europe Commission – The Power Of Sound – In Space

Heading out beyond Jupiter, the light from our sun gets very dim. And even close to home, space exploration can’t always draw power from the rays – e.g. on Mars, at night or during the planet’s fierce dust storms. Another option involves generating electricity from an inbuilt heat source. EU-funded research has combined acoustic waves and electromagnetism to do so.

The Space TRIPS project developed new technology to facilitate humankind’s ventures off-planet, and it has built a prototype to demonstrate the principle in practice.

“Space TRIPS focused on the production of electricity in space, by means of a system that has no mechanical moving parts,” says project leader Antoine Alemany of the SIMAP/EPM Laboratory in Grenoble, France. Alemany coordinated the project on behalf of lead partner Hekyom, a French SME specialising in thermoacoustics. Fewer moving parts means less wear and tear, a considerable asset for equipment designed to withstand the rigours of space or alien worlds far from the reach of a maintenance crew.

The proposed system is a combination of two engines, says Alemany – a thermoacoustic one, which transforms heat into mechanical energy, and a magnetohydrodynamic [MHD] one, which converts this mechanical energy into electricity.

Complicated? Not so, apparently. “The system is extremely simple,” he notes, conceding that it is, however, quite difficult to explain.

In short, in the first engine, the warmth from a heat source generates acoustic vibration in a gas – argon, in this case. In the second step of the process, these vibrations are transmitted to an electrically conducting fluid – Space TRIPS opted for liquid sodium. The motion of this fluid creates electricity, through interaction with an applied magnetic field.

Europe has considerable expertise with both technologies, but so far no one had ever merged them, Alemany adds. “The result is a completely new system that produces energy by induction,” he notes.

“In this process, the external coil where the electricity is generated has no physical contact with the internal part in which the liquid sodium is flowing. This core is completely closed and sealed off, which virtually eliminates the risk of leakage,” he says. “This is a very useful feature, ”he adds. “It is the first time that this kind of process has been performed.”

A sound solution

The concept is a radio-isotopic power system (RPS), a technology that exploits the heat generated by the decay of radio-isotopic elements to produce electricity.

Other designs are in use or under development, but the Space TRIPS solution relies on different technology, Alemany explains. One key difference with the latest concepts envisaged for such systems, he notes, is that these tend to involve mechanical moving parts such as a piston or a moving magnet, which the project’s MHD generator would obviate.

All systems go

The Space TRIPS prototype is scaled for a device such as a Mars rover, but this is not a limitation of the technology, Alemany notes. He is confident that the principle could be adapted for larger applications.

But it is, as yet, still early days. A prototype, however exciting, does not a spaceworthy system make. More investment, research and development time will be needed before Space TRIPS’ innovation is cleared for lift-off, says Alemany.

Following the end of the project in December 2015, the partners are now refining their prototype in order to boost its efficiency. They are also looking into possible sources of funding for the next stage in the development of their system.

Further financial backing would not just be an investment into humanity’s ventures into space. It would also open up new opportunities back here on Earth. Thermoacoustic technology is already on offer for various applications and could be used far more extensively, Alemany reports – for example, to generate electricity from solar collectors or waste heat that is typically lost.