
Sonic tractor beams that can lift and move objects using soundwaves - yitchelle
http://www.theguardian.com/science/2015/oct/27/the-force-awakens-tractor-beam-becomes-a-reality
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Natanael_L
Would be cool to see some ISS astronauts use something like an ultrasonic
transducer array to demonstrate this in front of cameras in zero-gravity,
pointing it against objects and making them spin and move forwards and
backwards at will. (Yes it could be done in high-altitude planes moving in
arcs too, but that's slightly less cool.)

Actually it could potentially even (if it doesn't use too much energy) be used
as a transport method for objects inside ISS, by having stationary transducer
arrays pushing objects to where they are needed. :)

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jychang
Sorry for being a wet blanket... but for some reason I don't think the ISS
will want high power vibration generators near all their sensitive
experiments.

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branchan
I think what you mean by "high power vibration generators" are just speakers.

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craigjb
It's too bad ultrasonic transducers this size (~16mm) are too large to make a
linear phased array with high angle range and low grating lobes [1]. This
means that a different object or particle might be manipulated simultaneously
with the target object.

I've been looking into using a genetic search or just brute force random
search to create a randomized transducer pattern that minimizes grating lobes
though. You can purchase these transducers in bulk for super low prices
though! So anyway to build a capable phased array with them would be awesome.

[1] [http://www.microwaves101.com/encyclopedias/grating-
lobes](http://www.microwaves101.com/encyclopedias/grating-lobes)

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hellbanner
Related: Putting out fires with a Bass Cannon

[https://www.youtube.com/watch?v=uPVQMZ4ikvM](https://www.youtube.com/watch?v=uPVQMZ4ikvM)

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anonymfus
I don't understand how British newspaper can put Star Wars references in the
article where Doctor Who is much more relevant.

[http://www.youtube.com/watch?v=fvhbGGkhKe4](http://www.youtube.com/watch?v=fvhbGGkhKe4)

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parfe
Probably because more people saw the last star wars film opening weekend than
have watched doctor who in its entire history.

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hellbanner
Can someone explain to me how sound waves can move something towards the
source of the wave?

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mtreis86
Not a physicist. I think, if you get a standing wave going, say on a drum
surface, and slowly change the frequency slightly up or down, a piece of rice
sitting on the drum can be moved around. The rice will tend to settle between
nodes. If you have significant enough energy, the interference patterns can
'drive' an object. Apparently this can be done in midair, with enough energy
to break gravity. And can be entirely controlled. Sweet.

Edit, spelling.

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DrScump
Originally posted here:
[https://news.ycombinator.com/item?id=10461771](https://news.ycombinator.com/item?id=10461771)

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Practicality
Too bad this wouldn't actually work between spacecraft since you need air
molecules (or some other medium) for the sound waves to work with. Still a
neat idea though.

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JoeAltmaier
WOnder if it works better or worse under water...

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Natanael_L
The core of this is the creation of spatially controlled pressure/density
gradients.

I believe you could impart greater force on objects under water more easily
due to its incompressibility, but then on the other hand you face greater
"inertiality" due to the density/mass of water, as well as the
resistance/friction/aerodynamics. I wouldn't want to guess anything beyond
that slow movements may be easier to achieve (quick small impulses) but that
fast movements would be harder.

The speed of sound also comes into play and which frequencies you thus have to
work with, and their propagation. Sound moves faster in water (related to the
incompressibility), so one wavelength corresponds to a higher frequency in
water than in air. This means you might also have to be closer to the
manipulated object (shorter range for the required frequencies).

Another thought is that this could be used in water as a means to propel
yourself without moving parts. Instead you just have surfaces acting like
speakers that create pressure gradients around your submarine to create a
waterflow directed backwards.

