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DerAlbi

Fri Feb 27 2015, 09:33PM

Registered Member #2906 Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727

Say the first stage will convert 5% of the electrical energy into kinetic energy and say another 5% are lost due to ESR, eddies etc.

Wow, you imply 50% eff at the first tage. Same amount transfered as lost.... would be record allready! Redo your example and assume 5%.
Then think again about the amount of energy that you put in the first coil. There must allready be all the energy present for alle the later coils. so you actually push 100J into the coil instead of 10J. As a consequence you are DEEEEEEEP into saturation.. so lets correct your efficiency to 1%.
Now redo your calculation again. Well: You need to push even more energy! ..lets correct the efficiency figure to 0.5%... continue your loop...

Uspring

Sat Feb 28 2015, 10:28AM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
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Posts: 711

Wow, you imply 50% eff at the first tage. Same amount transfered as lost.... would be record allready! Redo your example and assume 5%.

No. Consider a single stage. A 100% electrical energy in. The projectile goes through. 90% electrical energy is left in the coil (5% resistive loss, 5% kinetic energy). The 90% are lost, since the projectile has gone through. Efficiency is 5%.

But I think, what you are getting at, is that not 90% of the electrical energy is left, right after the projectile has gone through, but much less due to coil resistance losses. A TL ccelerator would not make sense for a stage with e.g. Q<1. Is that the case?

DerAlbi

Sat Feb 28 2015, 10:42AM

Registered Member #2906 Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727

Efficiency is "Kinetic / (Heat+Kinectic)". therefore you have 50%.
Your 5% is a conversion efficiency (=KinecticOut/MagneticEnergyIn). And 5% would be a pretty poor design. (assume 10-20%)

I dont kow what qualitiy factor implies.. i dont have a reference frequency.

Shrad

Sat Feb 28 2015, 12:15PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
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Posts: 780

DerAlbi wrote ...

Shrad:
the propagation delay is dictated by dielectric constant

How do you plan to slow down the pulse?
Getting down from 1/60 of the speed of light to even Mach 20 is a difference of 3 orders of magnitude.
you would maximize sqrt(L*C). The problem is, that C maximizes when L shrinks. (and vice versa) There is a practical limit to this. nothing you could influence or design with such freedom.

you could use L and C as a pulse forming network, or even with a secondary L and C at the junction of the primary L and C to lengthen the pulse so its duration is equivalent to the ideal projectile velocity, and pulse gets sharper as primary L gets smaller

If I was able to machine such a double spiral barrel I would really love to try this out, as I think a PFN with a pulse compression would be the most optimized design for a magnetically launched projectile

a bit like an electric trebuchet...

Uspring

Sat Feb 28 2015, 12:30PM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
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Posts: 711

Efficiency is "Kinetic / (Heat+Kinectic)". therefore you have 50%.

Ideally you'd have a large B, when the projectile is at the point where dB/dx is largest and zero B, when the projectile is at the center of the coil. During this interval the energy stored by the magnetic field has to go somewhere. Is it dissipated in the coil resistance or does it return to the driving electronics? If the latter, is it recovered there or just burned up? If it is recovered you'd have 2 ways to define efficieny. Either kinetic energy/initial electric energy, or you could put the difference between before and after into the denominator.

Q is a measure of damping of a tank, i.e. describes the percentage of energy lost during a cycle. A higher Q implies less damping. If you, e.g. add a resistor R in series with the inductance of a tank, Q would be:

Q=2*pi*fres*L/R

hen918

Sat Feb 28 2015, 06:55PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

Uspring wrote ...

...
Q is a measure of damping of a tank, i.e. describes the percentage of energy lost during a cycle. A higher Q implies less damping. If you, e.g. add a resistor R in series with the inductance of a tank, Q would be:

Q=2*pi*fres*L/R

what's happened to the capacitive elements?

Uspring

Sat Feb 28 2015, 07:20PM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
Location:
Posts: 711

You could write Q also as:

Q=sqrt(L/C)/R

using fres = 1/(2*pi*sqrt(L*C))

Signification

Mon Mar 02 2015, 10:04PM

Registered Member #54278 Joined: Sat Jan 17 2015, 04:42AM
Location: Amite, La.
Posts: 367

Shrad, On the TEA laser you referenced (impressive construction BTW), will the laser work while the water is flowing? I was also wondering what the purpose is of the tube mounted on the back of the laser. ...looks like quite a divergent beam.

Shrad

Tue Mar 03 2015, 08:14AM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

Signification wrote ...

Shrad, On the TEA laser you referenced (impressive construction BTW), will the laser work while the water is flowing? I was also wondering what the purpose is of the tube mounted on the back of the laser. ...looks like quite a divergent beam.

I think it would pose no problem but this is pulsed as energy is stored in the tubes and repetition rate is quite low so there would not be a need to flow the water

the genius part of that build is that the water is used as a self healing dielectric which acts as a spark gap... and all is coaxial which is the best thing in pulse power

what makes me think that the solution is to combine pulse power and simplicity is that such a TEA is actually one of the highest power to complexity ratio, is scalable, reliable and resilient which makes huge powers possible

DerAlbi

Tue Mar 03 2015, 08:49AM

Registered Member #2906 Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727

And yet the only realistic thing about it is the talk. Boring. Specially when there are guys involved who stuggle to understand the basic optimization parameter/goal "efficiency"..

You guys suffer from denail. You are blended by your own confidence and ideas. Having allready figured out that the mechanics of the barrel is the biggest problem one seems to neglect everything else which is obvious if you just would touch the topics that dont fit into this positive thinking. thats not engineering thats... actually i have no word for this. Maybe a B and a S.

Just put forward at least something realistic. What about a simulation (LTSpice?) of your so called "transmission line" with real ESR in the coils (L/R = 1..3ms).
I know its worth avoiding reality.. having a dream is much easier than living in the real world.

If this "transmission line"-style thing works its for now not important what kind of capacitor or whatever you use. Its basic electronics still. So it can be simulated.
Sure you guys have allready the circuit and models in mind.. or what is your confidence based on? So upload it!

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