The Witness - Wheels - - MOTORING - COLIN JEF­FREY

FU­TURE mis­sions to Mars may well be pow­ered by car­bon diox­ide-fu­elled 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, which is 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 alu­minium sur­face, where it floated on a pil­low of evap­o­rated gas vapour over a cir­cu­lar pat­tern of ridges, 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. With a se­ries of mag­nets and cop­per coils at­tached, the block of ice acts as an elec­tric mo­tor to cre­ate an al­ter­nat­ing cur­rent. This is the first time that the Leidenfrost ef­fect has been used to pro­duce any use­ful form of en­ergy, ex­plained Dr Gary Wells, a re­search fel­low in the depart­ment: Physics and Elec­tri­cal En­gi­neer­ing at Northum­bria Uni­ver­sity. On Mars, the alu­minium plate will be heated us­ing waste heat and ex­ploit the low boil­ing point of frozen car­bon diox­ide. — Giz­mag.com.

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