Sonic propulsion

[grooble]

Would sound waves move a spacecraft? I read that you cannot hear sound in space because there is no Air for it to travel on, so what happens to sound energy? If you put a huge speaker at the back of a spacecraft playin some rock music, what would happen?<br /><br />Also, whilst not related except in name, this is really cool aircraft:<br /><br />http://www.boeing.com/news/feature/concept/photok62068.html

 

[tap_sa]

<font color="yellow">" If you put a huge speaker at the back of a spacecraft playin some rock music, what would happen?"</font><br /><br />If it's on the outside of the hull then the speaker breaks down. Here's a good picture how most speakers work. If there is no air for the diaphragm ('cone') to push against then first base beats would rip the voice coil away. If you are lucky the ripped voice coil is ejected backwards and you do get <i>some</i> propulsion out of that. <img src="/images/icons/smile.gif" /><br /><br />If it's inside you'd serve beverages to raving hollywood starlets in your very first space disco!

 

[grooble]

This article says sound can travel through space - <br /><br />http://www.space.com/scienceastronomy/mystery_monday_030922.html<br /><br />What do you think?

 

[tap_sa]

Awesome scientific feat, no practical applications. Because space is not a complete void then it can convey pressure waves. The 'sound' detected from that black hole has <i>gargantuan</i> proportions. It's frequency is about three femtohertz (3E<b>-15</b> Hz), meaning time from one pressure peak to another is ten million years. I've no idea what the wavelength of this sound is but considering the distance from which it was photographed it's probably measured in light years.<br /><br />You cannot directly hear this sort of sound with anykind of ordinary microphone nor produce it with anything even remotely feasible by humans.

 

[severian]

Hmm, quite frankly, I don't think there is anything such as sound propulsion <br /><br />Think about it, all sound is, is variations in pressure (ie, pressure waves), which rise and fall. Think of a sine wave, the pressure increases, then it drop below the middle. That's why waves have frequencies, amplitudes, ect.<br /><br />There is no net change in momentum and hence, sound produces absolutely no thrust whatsoever, or if it does, it's only momentary, and that's due to the movement of the speaker.<br /><br />Sorry, but sonic propulsion simply doesn't exist.

 

[white_noise]

a crazy though:<br />if there is a special kind of material that can block air movement in an instance and let air through in another, the material can change state at a certain freq.<br /><br />when sound wave pressure is at it's peak, the material blocks air movement; when the wave pressure is at it's crest, the material lets air through. this way the material experience a net force. does this count as "sonic propulsion"?

 

[severian]

Well, even if you could, all you would end up doing is having a vacume between the material and the speaker, so that nothing more can get pushed out.<br /><br />What you would need is some way to push air into the gap, then have the speaker push it out the back. At that point, you might as well make a rocket engine.

 

[physicsobsess]

because space isn't really a true vacuum then if there was someway to control the diferences in pressure you could theoretically create a very small and VERY inefficient amount of force that might propel you foreward. think of a piston style air compressor, the piston is replaced by the diaphragm on a speaker and hypersonic valves or reed valves like in a two stroke engine could open and close letting air or gasses in from behind the speaker and letting the air out in front of the speaker but suck a method of propulsion would be so inefficient that it would probably work better to get one of those battery powered fans from walmart and glue it to the back of your spaceship, it would be simpler, cheaper and more efficient.

 

[neilsox]

Very low frequency "sound" = much less than 1 hertz propagates in space, with high path loss. I have not heard of sonic propulsion in our atmosphere, so it likely would work worse in the high vacuum of space. It should be possible to design a "speaker" to survive in a vacuum, but I can't picture it doing anything useful. Neil

 

[Valcan]

I hear by dub this thread the greatest zombie thread ever. Never seen one pass 4 yrs this one passed 5.