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Theoretical improvements for ETG?

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Ash Small

Wed Mar 06 2013, 01:34AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Yandersen wrote ...

-Honey, are you drunk?! You all smell like...
-Nommm, mum, I was j'ssst shootin' my eletramagun...

Well, Al foil, huh? 6.7 KJ per 1 gram of aluminum foil burned in oxigen - how about that "addition" to ETG "efficiency"?
Ethanol is 30KJ per 1g though. Methanol is slightly less and it is toxic.

If I can type I'm not drunk

Who wants to keep wrapping foil around the electrodes?

Just dump more power into it. Water is cheaper than ethanol, and still does the job.

Maybe I do have too much time on my hands these days, but I have to occupy myself doing something.

I'm sure you'll feel the same when you retire

EDIT: Sorry Yan, I missed 2spoons post. Nothing personal, but I have had a drink or three. (Use the 'Quote' button in future, it saves a lot of confusion.)

Ash Small

Thu Mar 07 2013, 01:14AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Actually Ethanol is quite a good suggestion. Other fuels could also be used, presumably those with a lower flaspoint would be advantageous, although, as long as it ignites, energy per gram would be a relevant factor, along with cost, availability, etc.

Personally, I see non-conventional fuels (eg water) as more of a challenge, and therefore more fun, but when it comes to increasing efficiency, ethanol is certainly a contender.

(sorry about the above post, we all have off-days. I'll try and bear that in mind more in future)

Yanom

Thu Mar 07 2013, 01:28AM

Registered Member #4659 Joined: Sun Apr 29 2012, 06:14PM
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how about adding some oxidizer in with all these fuel elements? kno3 (sold in a black bottle as Spectracide stump remover) might give it some more kick.

2Spoons

Thu Mar 07 2013, 02:05AM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
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Well, if you are going down that route you'd probably want to use hydroxylamine nitrate. Fuel and oxidiser in one. Unfortunately its toxic, and you'd have to make your own.

Ammonium nitrate would be a better candidate for mixing with an alcohol, it is far more soluble in methanol and ethanol compared to KNO3.

Reality is you'd be unlikely to get all the energy out of the fuel - you'd need to get the air/fuel ratio just right. Its still going to be better than water though.

Maxwell

Thu Mar 07 2013, 02:39AM

Registered Member #8497 Joined: Tue Dec 04 2012, 06:24PM
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Efficiency with chemical reactions becomes much more difficult to measure. Remember a chemical reaction is occurring. Total delta energy should remain constant regardless of input electrical charge - the input charge changes the rate of energy conversion in the chemical process.

I agree - using anything besides air plasma and water verges into the combustion propulsion category.

Yanom

Thu Mar 07 2013, 03:28AM

Registered Member #4659 Joined: Sun Apr 29 2012, 06:14PM
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hmmm, got another idea. Since you were going to use water anyway...

Drugstore hydrogen peroxide. It's 97% water by volume, so you have that. The remaining 3% is h2o2, which *may* decompose to h2o and o2 in response to the power surge. If it does, it will release oxygen gas and hot steam.

Yandersen

Thu Mar 07 2013, 03:53AM

Registered Member #6944 Joined: Fri Sept 28 2012, 04:54PM
Location: Canada
Posts: 340

Um, you guys keep forgetting that platinum electrodes resistible to oxidation and high temperatures are hard to find and buy...

Lets add some classification for those devices we are talking about.
As I understand, ETG (Electro-Thermal Gun) operates on the principle of heating propellant electrical way - so it is either air or smg non-combustible like water. If you use Al, ethanol or smg else, then electricity acts like an igniter only, so lets call those types EIG - Electro-Ignition Guns. Agreed?

Ash Small

Thu Mar 07 2013, 04:35AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Agreed.

Spark plugs are available with various electrodes (including platinum) and electrode coatings, but I'd only recommend un-suppressed plugs. I have some tungsten (TIG electrodes) and tantalum (wire) that I might try.

2Spoons

Thu Mar 07 2013, 04:47AM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
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I think the correct term is electrothermal chemical gun. or ETC.

Andy

Fri Mar 15 2013, 12:07AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
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This schemitc would be good for this type of thing. It uses microwave caps in parrellel and voltage/cap doubles each stage

arc thruster/railgun

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