Thermite Rocket?

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MJD
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re: Thermite Rocket?

Post by MJD » Thu Nov 17, 2005 5:55 pm

Thermite is a lousy rocket propellant. It produces a bunch of heat, but very little working fluid. For a rocket propellant to be powerful requires that it both release a lot of heat energy, and produce low molecular weight combustion products. That is why hydrocarbon fuels work so well, as the combustion products are relatively low molecular weight gaseous products - H2O, CO, CO2 - at chamber temperature and pressures. The most useful composite propellants combine a reactive oxidizer with relatively high oxygen content and low atomic weight constituents (of which AP has the best all-around combination of properties of the common oxidizers), plus a hydrocarbon fuel/binder, plus a dash of metal to raise the flame temperature without exceeding the gains of doing so by increasing the amount of solid/condensible products past the point of diminishing returns.

Thermite makes an excellent igniter however. Copper oxide/aluminum is a common igniter composition for experimental solid rocketeers. The field "rule of thumb" is 1/2 gram per 1000Ns of total impulse.

Mike D.

Greg O'Bryant
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re: Thermite Rocket?

Post by Greg O'Bryant » Fri Nov 18, 2005 3:36 am

Hay guys;

I was thinking of a hybrid type engine that use's carbonated water as the oxdizer and burned a metal like sodium,or magnesium even aluminum will react with water when it is hot enough. I understand that it may be hard to ignite such an engine but it is just a thought. what do you think? On a more realistic aproach what would be a good system to deliver liquid ox in a hybrid motor? Thanks

Greg O'Bryant
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re: Thermite Rocket?

Post by Greg O'Bryant » Fri Nov 18, 2005 4:22 am

Ben;
Some how I always get you to come out of the wood work:). First carbonated to eliminate the need for a seperate preasure generating system, and second an oxidizer in the fact that it will take electrons from the burning metal. I guess it is not a good term as it is actually a replacement reaction with the hydrogen in the water, but it still generates a lot of heat.

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re: Thermite Rocket?

Post by Greg O'Bryant » Fri Nov 18, 2005 6:06 am

Thanks ben"
That gives me hope that aluminum and water where used in a torpedo!
May be a waste of time but I like to try new things out at least in theory. Imagine an alloy of aluminum and sodium that would be easier to ignite than aluminum alone. The CO2 in the water may have a second function, not only adding preasure, it could also add exhuast gases as well as converting the hydroxides into carbonates. You would at least have a pretty yellow flame and could have pre-preashurized CO2/ water cylinders for the launch. I have shifted my interest into hybrids becuase of the legal problems asociated with premixed propellants. If you have any more info on the torpedo that would be great if not I will google it .thanks Oh ya about the bad timing I used to be known as the ruin'er in school.

Rambo
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re: Thermite Rocket?

Post by Rambo » Mon Jan 30, 2006 8:22 pm

I have some Al powder.Can someone tell me how to make a high preformance rocket fuel that don't blow up.

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re: Thermite Rocket?

Post by Zippiot » Mon Jan 30, 2006 9:40 pm

ur lookin at the wrong thermite. explosive thermite is the answer, its a mixture of zinc and sum oxide (cant remember ill look it up). dunno how explosive it really is, but if there is a way to slow down the combustion (salt or magnesium sulfate) then maybe it can be used in rocket fuel
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MJD
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re: Thermite Rocket?

Post by MJD » Tue Jan 31, 2006 2:50 pm

Considering that the thermite reaction consists of metalA reacting with metalB oxide to produce metalA oxide and molten metal B, thermite is probably the most useless candidate for a rocket fuel of any commonly known pyrotechnic mixture. It produces hot solids and or liquids. Rocket propellants need to generate gases (working fluid) to do their job. It is probably a good choice if all you want to do is melt a hole through your motor case without producing any useable thrust! Or to fuse your buddy's rocket to the launch rail while he's not looking.

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re: Thermite Rocket?

Post by bob000555 » Sun May 07, 2006 8:56 pm

thermite shouts out molton mettle...you'll distroy evrything and as the rocket rises(if it works) you,ll be sending the molton mettle even further, and imagen the molton metel coming out if the rocket should heppen to sipn :roll:

Axt
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re: Thermite Rocket?

Post by Axt » Tue Jul 18, 2006 6:11 am

While its correct that thermite type mixtures will never be high performance, they can actually work. MnO2/Al is a known propellant as the reaction is hot enough to boil manganese. PbO2/Al is hot enough to boil the lead and some Al2O3, but may be too explosive. HgO/Al would obviously form gasseous mercury :P again maybe too explosive not to mention toxic. CuO/Al is explosive but generates less gas then MnO2 and is more dense.

Al/MnO2 will generate 2645°C with phase changes, 4556°C without, where Mn boils at 2097°C (at 1 atm).

4Al + 3MnO2 -> 2Al2O3 + 3Mn + 1159cal/g (4651 cal/cm3)

Regarding Al/water, I had the idea some time ago to use KMnO4/fuel mixture to catalyse and ignite a mixture of H2O2/H2O/Al/guar gum, I made a prototype to test the reaction, it wasnt meant to actually fly
but it was never fired. I'll attach picture, essentually the oxidiser rich KMnO4/fuel fired in an inverted fountain down into the gelled peroxide fuel hopefully catalysing the peroxide with KMnO4/MnO2, generating enough heat/O2 to ignite the Al in a sustainable reaction. It was a long shot and I never did try it, though I did test the fuel for explosive properties and yep, when initiated with a detonator it detonated with a thunderous boom when in a 50% H2O2:Al ratio of 1:1 (this is balanced to Al2O3 + H2 products).


Pictures/movies attached of rocket, CuO2/Al being shot with rifle (its impact sensitive) and H2O2/H2O/Al/guar detonating.
Attachments
perocket2.jpg
The peroxide/Al rocket
perocket2.jpg (15.78 KiB) Viewed 12445 times
peroxide-rocket.jpg
the one I made but never used
peroxide-rocket.jpg (30.66 KiB) Viewed 12433 times
copper-oxide-aluminium-target.mpeg
Copper oxide / aluminium thermite being shot with .25-06
(880.58 KiB) Downloaded 504 times
peroxide-watergel.jpg
50% peroxide mixed with equal weight aluminium powder, gelled with 4% guar gum and detonated with commercial #8 detonator. Ok movie was 2.18mb and must be too big so this is a frame a bit after detonation, the detonation was just a big white out, you see
peroxide-watergel.jpg (4.18 KiB) Viewed 12434 times

bob000555
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re: Thermite Rocket?

Post by bob000555 » Tue Jul 18, 2006 6:43 am

Dude, why dont you try that rocket? Also a mixture of 2 MgO to 3 Al might work, but i wont try it because i dont want my yard coverd in molton metal :)
i know i cant spell well...you dont need to tell me

bob000555
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re: Thermite Rocket?

Post by bob000555 » Wed Aug 02, 2006 5:16 pm

Also if you move the KMnO4 colse enough to the gel the flame from the KMnO4/ fule contacts it it shoud burn and further break down would be catalysed by heat. Also this link has a thermite discosion and one of my stuped coments regarding MgO2 and Al but Al/CaCo3 does work. http://www.scienceforums.net/forums/sho ... php?t=7359
i know i cant spell well...you dont need to tell me

paul fellows
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Re: Thermite Rocket?

Post by paul fellows » Mon Apr 05, 2010 1:35 pm

from some one with no interest in rockets :(
just to stair things up a bit :twisted:
why ont try aluminium sulfide with zinc oxide :twisted:
a zinc sulfure rocket with a thermite kick :D
two test tickles

marksteamnz
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Re: Thermite Rocket?

Post by marksteamnz » Sun Apr 11, 2010 6:42 am

Quote (corrected) "why not try aluminium sulfide with zinc oxide"

Because you have as much knowledge of energetic chemistry as a lamp post

You might as well ask "why not try concrete with a dead fish"
Cheers
Mark Stacey
www.cncprototyping.co.nz

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