Future missions to Mars may well be powered by carbon dioxide fueled engines, thanks to a recent prototype developed by Northumbria and Edinburgh Universities. Exploiting a phenomenon known as the Leidenfrost effect, researchers hope that their engine could be powered by the vast amount of dry-ice deposits found on the red planet, thereby reducing the need to transport fuel on interplanetary missions.
The new type of engine proposed by the researchers takes advantage of the Leidenfrost effect, where liquid is brought into near contact with a surface that is considerably hotter than its own boiling point, a small portion vaporizes, and an insulating layer of steam is created that then protects the liquid above it from the majority of the heat. This layer then also acts as a levitating cushion on which the heated liquid floats and moves around.
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Commonly observed when beads of water dropped onto the face of a hot frying pan appear to canter across its surface, the phenomenon is exaggerated when the surface is composed of ridges, where the droplet effectively propels itself across the top of those ridges.
To create a prototype engine using this effect, the research teams were able to levitate a circular block of dry ice above a heated aluminum surface, where it floated on a pillow of evaporated gas vapor.
Underneath this arrangement, the surface over which it floated was ridged, but instead of the ridges being aligned in one way on a straight surface, they were arranged in a circular pattern, in effect creating a turbine. This meant that when the dry ice was subject to the Leidenfrost effect, instead of simply rolling across and off the surface, it rotated in a circle.
To this block, the researchers attached a series of magnets and copper coils that, when spun, acted as an electric motor and created an alternating current. This is the first time that the Leidenfrost effect has been used to produce any useful form of energy.
"The working principle of a Leidenfrost-based engine is quite distinct from steam-based heat engines; the high-pressure vapor layer creates freely rotating rotors whose energy is converted into power without the need of a bearing, thus conferring the new engine with low-friction properties," said Doctor Gary Wells, a Research Fellow in the Department: Physics and Electrical Engineering at Northumbria University.
While some other scientists have proposed exploiting the CO2 in the Martian atmosphere to power rocket motors, this system is significantly different. It doesn’t burn any fuel directly in the process to create energy. Instead, it could potentially use waste heat to take advantage of the Leidenfrost effect by exploiting the low boiling point of frozen carbon dioxide to spin a turbine to create electricity.
The team believes that this type of engine and the potential abundance of frozen carbon dioxide on Mars holds a great deal of promise for interplanetary missions, where it may be used to support lengthy periods of exploration or even colonization by exploiting resources natural to that planet.
"Carbon dioxide plays a similar role on Mars as water does on Earth," said, Dr Rodrigo Ledesma-Aguilar, a co-author of the Northumbria research. "It is a widely available resource which undergoes cyclic phase changes under the natural Martian temperature variations. Perhaps future power stations on Mars will exploit such a resource to harvest energy as dry-ice blocks evaporate, or to channel the chemical energy extracted from other carbon-based sources, such as methane gas."
"One thing is certain,” concluded Doctor Ledesma-Aguilar. "Our future on other planets depends on our ability to adapt our knowledge to the constraints imposed by strange worlds, and to devise creative ways to exploit natural resources that do not naturally occur here on Earth."
The results of this work have recently been published in the journal Nature Communications.
The short video below shows some of the development work conducted to create the prototype engine.
Source: Northumbria University