Sciencemadness Discussion Board - Rocket Fuel

Rocket Fuel

Truth - 30-6-2007 at 15:33

My friends and I are having a rocket car competition. We have a private field and have informed the authorities, so everythign will be safe. The cars are minature (about 18in long) we will not be rdign in them.

The competition is to see who can build the best (speed and distance) rocket FROM SRATCH. W cannot but anything prefabricated for rockets or similiar technology, but we can buy wheels, pipes, hoses, containers and such.

I need to think of a fuel to uses that will give me more acceleration than something like gasoline. It needs to be something that I can legally and safely make in my basement with limited technology, and won't cost hundreds of dollors to buy the materials. I thought of:

Black powder and sugar-but it blew up the whole car in trial 1

Ammonium perchlorate-But I can't think of a way to make it safely

Nitrogliscern and stabilizing clay- But I KNOW I can't make that safely

Kerosene-Not cool enough

Thermite- But I can't think of a way to get it to stick to the insid of a pipe and leave the middle open, it's difficult to ignite, and it may melt my rocket engine body.

Also I need a good oxidizer and perhaps a catalyst.

Nerro - 30-6-2007 at 15:53

Sucrose/KNO3 is a very good rocket fuel if properly prepared. So is sucrose/NaClO3 or sucrose/KClO3. The former is easier to make though, you can melt them together (outside of your house!) to homogenize the mix and then you can pour it so it will have an optimal shape e.g. a star-shaped hole in the center of the fuel-rod.

Geomancer - 30-6-2007 at 16:06

<p>You seem to have a rather poor understanding of how rockets work. Of the propellants you mention, kerosene and gasoline will fail because they are not energetic by themselves; they will only provide energy when combined with an oxidizer. Thermite will fail since it produces very little gas (it's not very energetic, either). Nitroglycerin adsorbed on clay is most likely to detonate, a result that is both useless and dangerous. Ammonium perchlorate is an excellent oxidizer, but it's not necessary to waste your effort obtaining it; plenty of more accessible oxidizers will work.</p>
<p>Assuming you can obtain the materials, my recommendations would be Zinc/Sulphur or Sugar(or sorbitol)/KNO3, in that order. Zn/S seem to regulate its own pressure, so can be more forgiving. Candy gives better performance.</p>

Be Safe.

[Edited to get paragraphs to work]

[Edited on by Geomancer]

Mr. Wizard - 30-6-2007 at 16:18

Kerosene isn't cool enough? = K3wl = young and foolish=accident waiting to happen. With that caution thrown in the mix to cool any foolishness I would suggest you Google the words: rocket candy sugar.

Please realize a rocket is a firecracker that doesn't blow quite up and holds just enough of the pressure to push a lot of gas and or hot solids out ONE end while maintaining enough pressure to keep the reaction going. If the reaction is too quick the pressure will rupture the container. Can you say explosion?

The trick, art, or skill is to keep the pressure in that safe and efficient zone, without causing an 'overpressure problem'. Can you say explosion? Some of the variables are the chemical mixture, the physical form of the mixture, the size of the nozzle, the grain shape, or if the moon is full.

Never stand next to a homemade rocket. Use the web sites you locate as a resource and ALWAYS realize you could be killed or injured if you make a mistake, and it's a lot easier to make mistakes than to do it right. Think about safety ALL the time. I would say learning to build good safe model rockets is the equivalent of learning to fly an airplane. You can always learn more and any mistakes can kill or maim you.

not_important - 30-6-2007 at 16:59

Hopefully the time to completion on this is waaaay out, as it is easy to get just a little overconfident with rockets and end up with major problems - like being pushed most of the way through someone's house.

You can use hydrogen peroxide all by itself
http://www.tecaeromex.com/ingles/peroxidoi.html
http://www.student.montefiore.ulg.ac.be/~teney/h2o2propulsio...

or H2O2 with a fuel
http://www.ad6uy.com/sac-l5/motor-test.html

http://www.the-rocketman.com/space-age-racing.html

little table of propellants
http://www.braeunig.us/space/propel.htm
Note that the highest performance combination listed is liquid F2+H2, but you'll kill everyone in the area.

Or you could go with a jet, which eliminates the weight penalty of carrying an oxidiser.

Xenoid - 30-6-2007 at 17:24

You sound like a bunch of plonkers!!!!

Why are you building rocket cars when you obviously know nothing at all about rockets!
Might I suggest you build steam powered cars instead!

If you still wish to go about this foolish endeavor, I suggest you check out Richard Nakka's excellent site and READ THE WARNINGS!

http://www.nakka-rocketry.net/

Xenoid

Marsh - 30-6-2007 at 18:41

First of all, YOUR best chance at a successful propellant is probably pressed BP running a KN of about 25, being that you more than likely know little to nothing about rocket propellant design.

KN value is the ratio of burning propellant area/nozzle throat area.

Each fuel has greatly different needs as far as typical working pressures, liner material, KN ranges, core design, erosive properties, burn rate etc etc. Not to mention the way a propellant reacts to pressure changes (usually known as pressure and burn rate exponents/coefficients). There are ways of testing and deriving these values to predict propellant performance.

You would need to learn all of this before simply saying "I want to make this go using this fuel."

There can be a lot of frustration delt with designing a rocket motor. A lot of testing is involved if you are pushing towards performance. You would be better off shoving a store bought motor in there and playing it safe, rather than blowing up your pretty little rocket car.

As far as performance fuels/binders, ammonium perchlorate 77%, aluminum powder 5%, and 18% HTPB binder + curative + plasticizer is simple and hard to match using most other fuels.

If you really want to talk business, I'd love to hear about anyones attempts using hydrazinium nitroformate and glycidyl azide polymer as fuel/binder, or any other fuel's pushing Isp's into the 300's.

franklyn - 30-6-2007 at 21:27

@ Mr.Wizard , remeber the film October Sky ?
http://www.imdb.com/title/tt0132477/

@Truth
Stay away from powders , their potential for ignition from static when dry makes
them somewhat risky and their tendency to be degraded as they absorb moisture
makes them unreliable. Perchlorate salts blended with melted polyethylene fuel
binder from recycled soda bottles , or Ammonium Nitrate and polystyrene foam
dissolved in acetone into a paste to allow mixing both , make waterproof
insensitive propellants.

But why re-invent the rocket ?
http://www.astronautix.com/articles/comlants.htm
Jato aircraft takeoff assist boosters cannot explode , these are KClO4 blended into
asphalt and is cast or pressed warm into a tubular casing using a fluted mandrel. In
the size you contemplate a reamer on an arbor should work well. When it has set ,
a hose threaded to the sealed end opposite to the exhaust end with the embedded
madrel forces salt water between the propellant matrix and the mandrel to release
it. This opening can later be plugged containing the electrically ignitable starting
composition such as smokless gun powder which you can get from shotgun shells.
Wash the cavity ( combustion chamber ) with naptha or paint thinner beforehand
and seal the tube with a plastic lid. It can fired just like that. Do not store this
indoors or for very long before launching.

Join a club near you to find out more , here's a useful resource _
http://www.hematoma.org/hist/ex-hist.html

The propellant GALCIT 61-C has the following composition: 76% potassium perchlorate
and 24% fuel. The fuel component was 70% Texaco No. 18 asphalt and 30% Union Oil
Company Pure Penn SAE No. 10 lubricating oil. Liquefied at 275°F the fuel and powdered
potassium perchlorate added to it are mixed and thoroughly stirred. The mixture is then
poured into the rocket casing and allowed to cool and become hard. This propellant,
when burned at a chamber pressure of 2,000 psi., has a chamber temperature of
3,000-3,500°F, a specific impulse of 186, and an exhaust velocity of about
5,900 ft. per sec.

.

Truth - 30-6-2007 at 21:46

1. For those of you who told me I am an idiot, thank you. It is not really clear to me why you think I am an idiot, other than my desire to build a rocket, because you merely mentioned something about not understanding fuels. If I understood how to make a fuel well, i probably wouldn't have asked what a good fuel was and how to make it.

2. Thermite will work if it is combined with a feed of pressurized gas. A rocket motor uses a parabolic cone to convert thermal energy into kinetic energy, which means the hotter the gas, the better the rocket. Preferrably, this gas would catalize the thermite reaction, but this is not necessary.

3. Those of you who told me to buy various rocket motors, I already told you, the point is to make it from scratch. Buying a motor means it would be MODEL rocketry, not AMATEUR rocketry.

4. I understand rocket fuels explode. I understand how to be safe with explosive substances. I understand I should be far away when I test the rocket.

5. If you are going to suggest a fuel, I need to know how to make it out of things I can buy at a drug store, not a science or hobby store. The point is to try this with everyday things. So while I know how t make KNO3 with a chemistry set, i don't know how to make it with $100 and a trip to walgreens or home depot.

6. It is my understanding you can not legally purchase hydrogen peroxide in any kind of pure form. I like in the USA.

7. How hot will a Zinc/Sulphur mix burn? Will it melt a stainless steel engine?

Twospoons - 30-6-2007 at 22:18

Xenoid has already provided you with one of the best net resources for building rockets. Go there. Read. Learn.
You need an oxidiser of some sort - KNO3 is one of the easiest to obtain - look for "stump rotter". Calcium or Sodium nitrate will also work, both are available as fertilizers.
Nitrate/sugar/sulphur a.k.a. 'candy propellant' will be your best bet for your first homebrew rocket.

not_important - 30-6-2007 at 22:55

Quote:

Originally posted by Truth
1. ... If I understood how to make a fuel well, i probably wouldn't have asked what a good fuel was and how to make it.

Given your rejection of kerosene, and some of your other ideas, this is obvious.

Quote:

2. Thermite will work if it is combined with a feed of pressurized gas. A rocket motor uses a parabolic cone to convert thermal energy into kinetic energy, which means the hotter the gas, the better the rocket. Preferrably, this gas would catalize the thermite reaction, but this is not necessary.

I think that you will find that the specific impulse of your thermite based rocket would be rather low. It would be even worse after including the mass of the source of pressurised gas. Getting good heat transfer to the gas would be difficult, too.

Plus there's the little matter that the temperature of reacting thermite is well above the melting point of most somewhat common materials, consider that one of the products is fused Al2O3, which melts at 2050 C. Those high melting points of the products can cause other probles, they would tend to freeze out on the nozzle, clogging it.

And what does "this gas would catalize the thermite reaction" mean? Thermite is self-contained, having both fuel and oxidiser, and hardly needs help to continue reacting. You're not going to find anything like that at the suppliers you mention.

Quote:

...

5. If you are going to suggest a fuel, I need to know how to make it out of things I can buy at a drug store, not a science or hobby store. The point is to try this with everyday things. So while I know how t make KNO3 with a chemistry set, i don't know how to make it with $100 and a trip to walgreens or home depot.

If you restrict yourself to these as suppliers, you're pretty much SOL.

Quote:

6. It is my understanding you can not legally purchase hydrogen peroxide in any kind of pure form. I like in the USA.

Canada is/has set up restrictions on the concentration of H2O2 ordinary humans may purchase. SFAIK the US has not yet done this. Even so, lower strengths may be concentrated by careful freezing to about 50%, and by distilling off the water under reduced pressure.

Quote:

7. How hot will a Zinc/Sulphur mix burn? Will it melt a stainless steel engine?

You can buy zinc and sulfur at the suppliers you mention?

The book of collected Amateur Scientist articles from Scientific American includes one on amateur rocketry, mostly zinc/sulfur fueled ones. Also see here http://www.vro.be/content/blogsection/4/135/lang,GB/

tito-o-mac - 1-7-2007 at 01:02

Maybe you should try out aluminium hydrazine, used for propelling the Tomahawk cruise missile in the second stage of flight. It burns twice as hot as gunpowder, and creates twice as much trust as gunpowder!

halogen - 2-7-2007 at 17:58

What is "aluminum hydrazine"?

Microtek - 2-7-2007 at 23:45

I think that for a beginner, Nakka's site may be a little daunting. If you stick to candy propellant, small engines and safe distances you really don't need to understand all the theory.
In my experience, candy propellant is very forgiving of Kn and other design variables, which means that it is a good propellant to experiment with. Also, since it is not a pressed powder, CATOs will not be as violent (as only a fraction of the propellant will contribute to the event).

I would suggest starting out at James Yawn's site. His method of making candy propellant (he calls it "recrystallisation") is safer than the classical way of melting the components together, and the product is excellent.

James Yawn's Website

MadHatter - 3-7-2007 at 10:07

http://www.jamesyawn.com

It's an excellent site for 'rocket candy' based rockets. His method for making the fuel
is safer than the traditional melting technique.

BTW, the aluminum-hydrazine fuel combination is a slurry or gel of powdered aluminum
in hydrazine. I just can't imagine a novice trying to create let alone use this fuel.

[Edited on 2007/7/3 by MadHatter]

Marsh - 5-7-2007 at 13:15

Truth, first of all I think you should listen to some of the things we are telling you, rather than portraying what you want to hear.

You go on to explain what you know, further proving that you know even less. Be open-minded, please.

No, gas temperature is absolutely not the determining factor of Isp. This is why you are so stuck on thermite it appears. Actual gas output from the reaction is the biggest factor, as well as whether there are solids in the exhaust products or strictly gases. A propellant with 100% gas output will typically perform more efficiently than a similar propellant with solid particles in its exhaust. A small metal content in the propellant will help raise Isp, as it increases temperatures in the reaction zone and thus does help with gas output and thorough fuel consumption. Too much metal will slag through the nozzle and also slow burnrates due to the temperature damping effect it has in greater concentration.

Now let's get things straight here, you are discussing rocketry, through the years it has become much more unlikely that you will find materials for building worth-while rockets at the local conveinient store, that's just the cold hard truth. So, you should either give up on this idea, or pursue it with intentions that you may need to order some proper materials.

One thing is, rocketry requires a bit of learning to pick up successfully. You can learn basics and assume, use easy fuels etc, but until you get a depth of understanding in your mind you will not produce great results. That is, assuming you want to play around with 200+Isp fuels and not blackpowder.

I could not recommend a better book for beginners than Terry McCreary's book, "Experimental Composite Propellant". Everyone points to Nakka, but he is an ammonium nitrate guy, and I personally feel that AN has some pains that just don't make up for anything that has to do with using it. AP will produce higher Isp's more easily and is not hygroscopic, also much more elastic and forgiving under pressure spikes.

Xenoid - 5-7-2007 at 16:13

Quote:

Originally posted by Marsh
Everyone points to Nakka, but he is an ammonium nitrate guy, and I personally feel that AN has some pains that just don't make up for anything that has to do with using it. AP will produce higher Isp's more easily and is not hygroscopic, also much more elastic and forgiving under pressure spikes.

Actually, Richard Nakka is a KN guy, I don't think he even mentions AN on his site!

AN is extremely hygroscopic, but the main problem is expansion/contraction of the grain due to phase changes occurring at normal operating temperatures. Phase stabilisation by the addition of certain chemicals can overcome this problem!

Nakka deals with KN/sucrose/dextrose/sorbitol/epoxy compositions.

Xenoid

Marsh - 5-7-2007 at 19:22

Quote:

Originally posted by Xenoid

Quote:

I stand corrected. I don't know why I was thinking he delt with AN but I was. I believe I was actually thinking of this site instead: http://www.space-rockets.com/psan-i.html

Twospoons - 5-7-2007 at 22:23

I bought the Wickman book some years back. Good book! Lots of info, and a step-by-step method for creating and characterising the propellant, then designing and building a motor with it. Had some good (simple) software with it too.

tito-o-mac - 6-7-2007 at 06:11

Just buy one rocket motor yourselves, its much safer and legal, and saves yourselves from concocting deadly chemical recipes rather than blowing off your fingers/eyebrows or whatever body parts. If you have trouble, you can contact YT2095 because he's a member of the British pyrotechnics

tito-o-mac - 7-7-2007 at 00:31

Have you heard of one of the Mythbuster's shows(discovery channel, Wednesday 9pm, Hong Kong timing) that they had attempted to build a rocket with salami?

YT2095 - 7-7-2007 at 01:45

Quote:

Originally posted by tito-o-mac
Just buy one rocket motor yourselves, its much safer and legal, and saves yourselves from concocting deadly chemical recipes rather than blowing off your fingers/eyebrows or whatever body parts. If you have trouble, you can contact YT2095 because he's a member of the British pyrotechnics

no you may NOT contact me! and you have NO RIGHT to "Volunteer" me for that either! :mad:

you do NOT give permissions like that without asking me FIRST! EVER! :mad:

------------------------------------------------------------------------------

now then, back to the reason I was going to reply.
we also have rocket car competitions, along pretty much the same rules, there`s nothing pre-made for rocket cars, they must be made from scrap and bits of junk.
However, the engines used ARE factory made.

the reason being it keeps the Challenge fair (as well as safe), each competitor is issued with identical rocket engines. the Skill comes from the design of the car itself then.

as mentioned above, there is Very little fundamentally different between a rocket and a pipe bomb!.
you`re much better off buying your own engines!

quicksilver - 7-7-2007 at 06:14

Quote:

What happens when they blow their fingers and eyes all over their workshop? Can they simply blame it on YT2095? I am being quite ludicrous of course but that IS setting the guy up for a law-suite or a trip to jail, etc.....I don't think that a very good idea. Better they do their own research with that sort of thing. Particularly in this day and age.