Sonic tractor beams that can lift and move objects using soundwaves | Hacker News Reader

Sonic tractor beams that can lift and move objects using soundwaves

theguardian.com

53 pointsyitchelle18 comments

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. :)

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.

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

Actually, I think this is much cooler on Earth, where it can "defy" gravity :)

I imagine it would be easier in space to create things like games out of it, such as sonic bowling or "air hockey", or maze solving.

How would that work since there is no sound in space? As I understand, sound vibrates against molecules drifting around and since those molecules don't exist in space, it wouldn't work.

Because it would be done inside the space shuttles

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

Related: Putting out fires with a Bass Cannon

https://www.youtube.com/watch?v=uPVQMZ4ikvM

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

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

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

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.

Because you control the air pressure waves (sound) well enough that there's a pressure peak (slightly more dense air) right behind the object, with lower pressure in front of it (less dense air) on average.

That would force it to move towards you if you can overcome any friction and other counteracting forces.

Originally posted here: https://news.ycombinator.com/item?id=10461771

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.

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

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.

Reply on news.ycombinator.com