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Large solid fuel motors

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Before I get into this, let me say what a great forum this is. Good to see so many other people with a similar interest sharing useful information.

I have a question regarding large, solid fuel motors.

I have a design for a large rocket, specifics being 4m high, 110mm OD body with an esitmated weight of 100KG, excluding the motor. The whole design is based around the principle of using a single use solid fuel motor to power the rocket, with an OD of the motor casing not exceeding 100mm. The motor can be up to 3m in length, but there is considerable room for design tweaking if it needs to be longer, however there is no room for extended width.

The motor needs to be long burning, 30 seconds minimum, which produces in excess of 500Kg thrust for the entire duration of the burn time.

Has anyone built a motor, from scratch, this large before?

Can it be done?

I estimate that heavy guage spiral wound cardboard tubing could be used for the motor casing - I have obtained samples of 15mm wall 100mm OD tubing which is very robust, and a 65/35 mix of KN/Sorbitol could be used for the fuel, due to it's uniform flat thrust curve characteristics.

Any information appreciated.

Thanks,
Dutch
 

Missileman

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I don't think any cardboard tube no matter how robust would hold up to a 30 second burn.
I would think an extremely long burn could not be accomplished with a core burning motor under 100mm dia.
That leaves a long baits grain, but heat at the aft end after several seconds into the burn would be extreme.
Why in the world do you want such a long burn?
Are you trying to achieve orbit?
 

utahrc

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Are you trying to achieve orbit?
My guess is that this individual is looking for a more horizontal flight path than we are accustomed to.
 

Karl

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Originally posted by missileman
I don't think any cardboard tube no matter how robust would hold up to a 30 second burn.
I would think an extremely long burn could not be accomplished with a core burning motor under 100mm dia.
That leaves a long baits grain, but heat at the aft end after several seconds into the burn would be extreme.
Why in the world do you want such a long burn?
Are you trying to achieve orbit?
I agree , NO cardboard tube (No matter how thick) would hold such a long burn time! Yep the aft end would become EXTREEMLY hot , and would cause alot of problems! And 30sec burn time wouldn't half give that rocket a BOOST ! (So much so that you proberley wouldnt see that rocket again for sure ! And excessive altitudes would be gained here , so some sort of goverment go-ahead would be needed lol! )
-Karl
 

wwattles

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I'm inclined to agree. When you start talking about a 30-second-plus burn, with a 4.3 inch body, 13 foot length, 220 pound weight, 500+ kg thrust and 3/4 of the total body is motor (leaving only 3 feet for parachute, tracking, etc), you have something that is going to go so high that you can't track it, and so far you can't recover it, and come down so fast you can't reuse it. And that's if you launch it straight up!

WW
 

Karl

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Yeh the biggest 'chute you can have is 3ft , now look at the Gates Brothers rockets , they dont even launch on that size of motor! And there rockets come down on 23ft 'chutes and still come down fast (But dont break because they make 'em STRONG!)
-Karl
 

sandman

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Dutch,

I see you haven't replied to any of these comments.

Are you pulling our legs?

What is your REAL motive???

We have had..."intruders" here in the past. So we are a bit suspicous.

I noticed you don't give your location???

Why am I not suprised?

What you are proposing sound more than a little dangerous and not in the spirit of the hobby.

Sorry if this seems harsh but this project just seems "extreme for a first post.

These are dangerous times.

sandman
 

Ryan S.

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Amen to that sandman. and cardboard definantly wont work
 

JasonF

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with an esitmated weight of 100KG, excluding the motor
So what on earth is making a cardboard tube rocket this heavy? Either were getting really popular with a certain political group, or were being tested.
 

powderburner

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I would like to suggest that the moderators consider adding one more section titled "Too Hot to Handle."

This would be a special section reserved for all the questionable questions and all the posts that look too stinko. Perhaps give the TRF members an opportunity to assist in self-policing by allowing us to vote on moving any suspicious threads to this new category (maybe requires five TRF members, each with more than 100 posts, to confirm this transfer?).

As it is now, you moderator guys get to have all the fun.
 

WiK

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Whoa... Your wanting to put a motor that big in CARDBORAD?!?


Have you got any designs for the rocket on your pc? Rocksim, Spacecad, 3d drawings? Maybe just a scanned in design on paper...


And what are you trying to acheive with this?
 

Guest
Guys, thanks for all the responses.

I see you haven't replied to any of these comments.
I haven't replied as of yet because im in a different time zone to you.

Are you pulling our legs?
No

What is your REAL motive???
Real motive? If you mean "am I planning on building a long range missile with an explosive warhead", then NO. My intentions are within the sphere of amatuer HPR, not terrorism. However your concern is appreciated.

As I should have said in my inital post, I am new to motor design and construction, and not a veteran by any means of rocket design, hence what may seem dumb or 'questionable' questions.

The rocket design is a test bed for a new active guidance system I have designed and bench tested. The reason for high thrust long burning motors is the need to tax the system to the maximum, for a long enough period to obtain sufficient data. Further, more than one test of the system is required during flight, since there are many subsidiary and auxillary stages within the guidance computer itself.

Bulky, additional equipment is needed to relay all this info to the ground, which bumps up the rockets weight to well beyond what the finished model would be, thus the need for what may seem extreme thrust requirements.

If you would prefer me not to discuss this matter on these boards, I shall take myself elsewhere. I don't what to raise any eyebrows or cause a nusiance.

Dutch
 

Chilly

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Originally posted by Dutch
The rocket design is a test bed for a new active guidance system I have designed and bench tested.
[/B]
Sorry pal, but you just said the magic word. "Guidance" is strictly forbidden under TRA & NAR safety codes and is the primary difference between a high-power hobby rocket and potential weapon. We won't touch that one with a ten-foot pole and would be setting our hobby up for tons of trouble if we did.
 

Stones

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Dutch...
However "admirable" your attempt at conceiving this project may be, this is NOT the right forum to look for answers. Nuff said.
 

sandman

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As it is now, you moderator guys get to have all the fun.
Sure...all the moderators are at the Whitaker launch this weekend!:mad:


Dutch,

Unfortunately no matter how honest and forthright you are..."guidance" is a NO-NO in model, high power or EX rocketry.

You are just going to have to shelve this experimental idea for a time when you can get a job for Raytheon or Boeing.

The hobby has been strickly self-regulated for a very long time and has a stellar safety record.

The rocketry community and various government agencies have decided that "guidance" is just not a hobby appropriate road to travel.

The government has stepped in after 9/11 and paranoid minds are just looking for an excuse to end our hobby.

So come on in here and build some kits and have some fun.

sandman

P.S. Oh yea...post pictures...we like pictures:D
 

gerbs4me

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you should put this project away for awhile, but since you mentioned "guidance" don't even think about it. sorry but rules are rules.
 

KermieD

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Not *all* of the mods are at Whitakers! ;)

Dutch, as has been said, active guidance is a real no-no in this hobby. While I don't know if I'd have gotten into your face as much as some here have already, it still raises a red flag when someone brings this topic up.

I'm leaving this thread where it is, but locking it. At least as long as it stays on the front page, it might serve as a reminder that this topic goes well beyond the intent of the forum.

All that being said, I hope we haven't run you off. Your questions and input on topics that are more pertinent to our discussions here are welcome and even encouraged. As a reference, "how-to" on homebrewed motor construction, discussions on active guidance, and blatantly political threads are off-limits. Stay off those and play nice with the rest of us fanatics and we'll all get along great! :)

-Jon
 
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