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Sonic Bullets (Metamaterials)

Posted by: sanman - Thu Apr 08, 2010 5:49 am
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Sonic Bullets (Metamaterials) 
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Post Sonic Bullets (Metamaterials)   Posted on: Thu Apr 08, 2010 5:49 am
http://nextbigfuture.com/2010/04/sound- ... ed-by.html

So in the wake of metamaterials being developed for optical purposes, they have also been developed for acoustic purposes. It may soon be possible to have metamaterials which generate ultra-high intensity soundwaves ("sonic bullets") which can travel through the air, or water, or other materials.

I'm wondering if this could somehow have aerospace applications.

For instance, would it be possible to use such high-intensity soundwaves to protect a spacecraft during re-entry, or protect a hypersonic craft during hypersonic flight?

We've already heard of the idea of the plasma heat shield, and also the idea of using a plasma torch to facilitate the passage of supersonic aircraft. Could extremely intense soundwaves from an acoustic metamaterial do something similar?

Alternatively, since we know how crucial the turbopump is to rocket engine operation, would it be possible to use intense soundwaves for compression instead of a turbopump? Could we use metamaterials to achieve this for more reliable operation, instead of depending upon a turbopump which could fail catastrophically?

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Post Re: Sonic Bullets (Metamaterials)   Posted on: Fri Apr 09, 2010 12:40 pm
Possibly it could be used on subsonic aircraft to accelerate or otherwise mess with the boudnary layer and reduce drag.

Heatshields are already shielding against sonic shock. It would be hard to add anything to pressure waves of that magnitude, even harder to emit sonic waves ina hypersonic regime.

For the turbopump replacement, what would your power source be? A Turbopump is its own power source.

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Post Re: Sonic Bullets (Metamaterials)   Posted on: Fri Apr 09, 2010 7:04 pm
Well consider that for reusability, you know that things like heat shields are the least reusable, either being ablative and thus requiring immediate replacement, or else having a lifespan for only a few runs.

Whatever's taking the most punishment is going to be putting limits on overall system reusability. So whatever mechanism you can devise to shield these components from maximum punishment can then increase the reusability and thus lower costs. Sure, your heatshield would still be there behind it as a safeguard, just in case that mechanism failed. But if your mechanism is working fine for the most part, then your heat shield isn't seeing wear-and-tear for the most part, thus keeping things happily reusable.

As for powering a replacement for a turbopump, I don't know, maybe this thing would actually be supplementing the turbopump instead of replacing it, so that the turbopump operates under less stressful conditions, thus extending its operating life. So perhaps it could draw power from the turbopump to do this.


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Post Re: Sonic Bullets (Metamaterials)   Posted on: Sat Apr 10, 2010 11:29 am
I don't see how any sort of sonic emitter would function as a heatshield.

The main source of heating is radiation from exotic chemical reactions heated by shock. Can either re-radiate the heat, the way the shuttle does, you can bleed it off by chemical decomposition the way an ablative shield does, or you can use some sort of active or transpirational cooling.

Even if you did manage to add some sort of extra boundary layer the radiation will got straight through it.

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Post Re: Sonic Bullets (Metamaterials)   Posted on: Sun Apr 11, 2010 8:04 pm
Well, then what about some other application, like aero-braking?

Capsules have blunt-body geometry for aero-braking, while Shuttles have their lifting winged bodies. SpaceShipOne has its V-hinge for stability. Each has its trade-offs.

What if you could use acoustics for steering, control, or even braking?

What if you could even fire off "lifting bubbles" of sound energy from the ground station, to help slow down the vehicle during its descent? You might need some specialized surfaces on the vehicle to catch these soundwaves being fired at them.

Alternatively, your soundwaves could carve a channel through the atmosphere, to allow the re-entry vehicle a safer and less heated passage down to the thicker atmosphere which can give more braking and less heating.


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