- Being Single Is a Drag for Exploding Spores
- Utah Is Perfect for Pretending You Are on Mars
- Flying Robot Swarm Takes Off
- High-Speed Videos: The Hidden World of Insect Flight
Posted: 27 Sep 2010 04:11 PM PDT
Fungi don't need a weatherman to know which way the wind blows. They make their own. Forcibly ejecting thousands of spores into still air creates a little puff that can carry the fungal offspring 20 times farther than a single spore travels alone, researchers report online the week of September 27 in the Proceedings of the National Academy of Sciences. By working together to stir the air around them, the spores can dodge nearby obstacles such as leaves, reach other air currents, and ultimately land on real estate prime for infection.
Using high speed video, a team of researchers from Harvard, Cornell and the University of California, Berkeley, clocked the launch speed of spores of Sclerotinia sclerotiorum, an omnivorous fungus that attacks numerous plants. The spores initially blasted off at speeds near 20 miles per hour. But the distance they traveled depended on whether they launched alone or en masse. Spores sprung singly were quickly brought down by drag, traveling a mere 0.1 inches before decelerating to zero. But when the fungus ejected waves of spores in quick succession, it created currents that carried spores farther at a slow but steady pace of just over 1 mile per hour.
Modeling these fungal ballistics revealed that every spore doesn't get to take full advantage of this group-generated gust. Spores that launch first set the air in motion, but don't travel as far as their peers.
When the fungus Sclerotinia launches its spores, the first ones to emerge (blue, on right) create a wind that carries subsequent spores (yellow) higher. The last spores to emerge (red) can fly as high as 20 centimeters, much farther than any single spore could go by itself.
Image and Video: Mahesh Bandi, Agnese Seminara/Harvard University and Marcus Roper/UC Berkeley
Posted: 27 Sep 2010 10:58 AM PDT
Six wannabe Martians are are taking life on Mars for a test drive here on Earth. In a small cylindrical building in the Utah desert, the would-be space explorers live every moment as if they were the first human outpost on the red planet.
The group is sponsored by the privately-funded Mars Society, a nonprofit whose main goal is to send humans to Mars as soon as possible. NASA is still figuring out when and how the first Martian envoys will get there — Obama's latest vision would get humans into Mars orbit around 2035, relying on private aerospace companies to do the heavy lifting.
But the Mars society doesn't want to wait that long. The organization runs two Mars Analog Research Stations, one in the Canadian Arctic and one in Utah, and has plans for a third in Iceland.
The Utah desert, with its barren expanses of rust-colored dirt, looks like it could well be an alien planet. The station is manned by six Mars enthusiasts (some scientists, some not) who live as close to the way they would on Mars as they can: gearing up in spacesuits whenever they venture outside, eating dehydrated food, and worrying about shower and toilet water.
There are some obvious holes. Pancakes probably flip differently in Martian gravity, and the town of Hanksville is a mere 20-minute drive away — Henry David Thoreau was more isolated at Walden Pond. But the participants take it seriously, and hope to build support for the idea of human life on Mars.
Posted: 27 Sep 2010 10:24 AM PDT
By Olivia Solon
The Ecole Polytechnic Federale de Lausanne in Switzerland is developing swarms of flying robots that could be deployed in disaster areas to create communication networks for rescuers. The Swarming Micro Air Vehicle Network (SMAVNET) project comprises of robust, lightweight robots and software that allows the devices to wirelessly communicate with each other.
The flying robots were built out of expanded polypropylene with a single motor at the rear and two elevons (control surfaces that enable steering). The robots are equipped with autopilot to control altitude, airspeed and turn rate. A micro-controller operates using three sensors — a gyroscope and two pressure sensors. The robots also have a GPS module to log flight journeys.
The swarm controllers running Linux are connected to an off-the-shelf USB Wi-Fi dongle. The output of these (the desired turn rate, speed or altitude) is sent to the autopilot.
For the swarming, robots react to wireless communication with either neighbouring robots or rescuers, rather than relying on GPS or other positioning sensors that might be unreliable, impractical or expensive. Software algorithms that know where other nearby bots are can stop them from crashing into each other.
Designing swarm controllers is generally quite challenging because there is no clear relationship between the individual robot behaviour and the resultant behaviour of the whole swarm. The researchers therefore looked to biology for the answer.
Army ants were used as inspiration for SMAVNET, since they lay and maintain pheromone paths leading from their nests to food sources. Similarly the flying robots are required to lay and maintain communications pathways between a base node and users in the environment.
Robots can therefore be deployed as "Node MAVs" and "Ant MAVs". The node MAVs spread out to create a grid onto which virtual pheromone can be deposited and detected through local communication. To maintain their position they turn on the spot describing a 10m radius circle.
Ant MAVs then travel along said grid, communicating with the nodes as they travel along them to explore further air space. When the Ant MAV reaches a position in the grid that is not occupied, it becomes a Node MAV, thus extending the reach of the grid until connection with the target user in the environment is achieved.
EPFL has so far experimented with 10 flying robots, which they believe to be the most robots to be flown together as a swarm to date. Check out the video of the project below:
Posted: 27 Sep 2010 04:00 AM PDT
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