TWIE 113: Lasers Create Rain

This Week in Engineering - Extinguish fire with sound; geoengineering shade in New Mexico; rechargeable lithium air batteries; lasers create rain; searching for lunar water; and mind-controlled video game.
 
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Transcript For This Video

Extinguish fire with sound
Darpa has been looking at unusual methods of firefighting as part of their Instant Fire Suppression program since 2008, and by approaching the problem with physics instead of chemistry, they have now shown that sound waves can extinguish a flame. At specific frequencies, the air velocity increases, causing the flame boundary layer to thin, allowing the flame to be easily disrupted. Say, wouldnÆt it be great if the firefighting frequency could only be found in a Nickelback CD? On second thought, IÆd really rather burn.

Geoengineering shade in New Mexico
Engineers from Harvard are planning to study the effects of a simulated volcano eruption, by deploying sulphate aerosols into the stratosphere from a balloon 80,000 feet above New Mexico. The particles would reflect some of the sunÆs energy back into space, decreasing the temperature of the Earth, as part of a controversial geoengineering approach to combating climate change. The experiment would study the effects of the aerosols on the ozone layer, and follows a similar British project of dispersing stratospheric water vapor that was eventually canceled. Stratospheric aerosol tests in New Mexico? Bad idea. To study the effects of aerosols on the atmosphere, just test New Jersey. ItÆs what theyÆre for.

Rechargeable Lithium air batteries
Researchers lead by Peter G. Bruce from the University of St. AndrewÆs in Scotland have announced that they have demonstrated a lithium-air battery that can be recharged without degrading the electrode. Lithium-air batteries operate by combining lithium ions with oxygen at the cathode, producing lithium peroxide, and are much lighter than lithium-ion batteries, in which lithium ions move from cathode to anode through an electrolyte. The work is in the very early stages, but could one day enable batteries that have up to five times the energy per unit mass of todayÆs lithium ion batteries.

Lasers create rain
Cloud-seeding techniques, especially using particulates, are nothing new, and last year, scientists published results for creating tiny water particles from moderately humid air by firing a laser beam. Now, a scientific paper has analyzed the effects of rapid improvement in laser technology, and suggests that one day lasers could create condensation. The technique works through photodissociation, where photons break down compounds and release ozone and nitrogen oxides, which causes nitric acid particles to form and bind water molecules together.

Searching for lunar water
While weÆre all looking forward to the Mars Curiosity rover landing, NASA and the Canadian Space Agency are testing a lunar rover for finding water and other natural resources on the moon. The Regolith and Environment Science and Oxygen and Lunar Volatiles Extraction, or RESOLVE, will hopefully determine if the moon has enough water for a prolonged or permanent manned station. Such a mission would follow up on previous data suggesting ice exists in the moonÆs polar regions. IÆm all for space missions, but as a lunar conspiracy theorist, I think this is all just a ploy to mine the universeÆs most exotic ice cubes for Richard BransonÆs scotch.

Mind-controlled video game
Charles Moyes and Mengxiang Jiang from Cornell University have built a version of the video game Pong, where the game controller is replaced by an EEG device that monitors alpha waves coming from a playerÆs brain. Alpha waves increase with concentration and decrease with relaxation, and the player moves the paddle up by relaxing, and down by concentrating. So, wait, now we can play a racket-and-ball game without so much as moving a video game controller? Man, engineers will do anything to not go outside.