Rcandy Aerospike

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Greg O'Bryant
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re: Candy rocket rules of thumb

Post by Greg O'Bryant » Fri Dec 30, 2005 8:22 pm

Wow is that a first? To use rocket candy and a spike? very nice

madmike
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re: Candy rocket rules of thumb

Post by madmike » Fri Dec 30, 2005 10:03 pm

After you reground the knos/sugar mix for maximum surface area for your maximum burn rate, did you just fill your motor chamber or did you press it in firmly?

P.S. Even though these guys hijacked my thread for this off shoot of a subject. I still can learn new stuff. Feel free to do it anytime.I don't mind a bit. By the way, do you know what your reusable rocket casing weighs?Just curious great video and thanks again for sharing the new info to me(us).
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steve
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Re: re: Candy rocket rules of thumb

Post by steve » Fri Dec 30, 2005 11:09 pm

madmike wrote:After you reground the knos/sugar mix for maximum surface area for your maximum burn rate, did you just fill your motor chamber or did you press it in firmly?

P.S. Even though these guys hijacked my thread for this off shoot of a subject. I still can learn new stuff. Feel free to do it anytime.I don't mind a bit. By the way, do you know what your reusable rocket casing weighs?Just curious great video and thanks again for sharing the new info to me(us).
the powdered fuel was pressed into the casing firmly so that it will hold its shape (it is fairly sticky once handled a bit). if you compact it enough you can even drill into it if you are careful.

the casing: 76.4g
aerospike nozzle: 35.0g
bell nozzle: 32.8g

I'm not sure if this is the first aerospike run on Rcandy, I only know of one other amateur attempt and I'm not sure what fuel was used. There have been several engines built by colleges that burned solid fuel, but it was probably AP based.

MODERATOR:
could someone break the aerospike stuff away as a seperate thread so I'm not hijacking this one?
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steve
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Re: re: Candy rocket rules of thumb

Post by steve » Fri Dec 30, 2005 11:14 pm

HattoriHanzo wrote:Very nice!
Do you know the exit pressure of the nozzle?
Unfortunately I can only make an estimation. I think it may be somewhere between 800 and 1000 psi
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re: Rcandy Aerospike

Post by Mike Everman » Sat Dec 31, 2005 7:39 am

Man, Steve, that looks like a huge success! hot dawg, very thought provoking! Nice work.
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Ray
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Re: re: Candy rocket rules of thumb

Post by Ray » Sat Dec 31, 2005 5:22 pm

steve wrote:
HattoriHanzo wrote:Very nice!
Do you know the exit pressure of the nozzle?
Unfortunately I can only make an estimation. I think it may be somewhere between 800 and 1000 psi
I would be very surprised to learn that the exit pressure of the nozzle was that high...it is supposed to be atmospheric. I would believe the chamber pressure was that high. I am sure that's what you are talking about.

Nice motor. The spike seems to work very well, no evidence of over/under expansion.

If you really want to study this, set up for a static test stand. Get precise in your mixutures and weights and study it. I am doing the same thing with standard nozzles and 75mm hardware. Some interesting results.

You can get strain gauges from Richard Nakka's site, and digikey carries a pressure transducer (variety of pressures) for a bit over $100 US. The part number of the one I am using is MSP6252P5-1-ND.

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re: Rcandy Aerospike

Post by HattoriHanzo » Fri Jan 13, 2006 5:33 pm

Is this pressure transducer useful on a rocket engine? The temperature range is way out of its limits. But maybe it can withstand 1400-1500K for a short duration of time?
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re: Rcandy Aerospike

Post by Ray » Fri Jan 13, 2006 7:04 pm

you'll have to protect if from the heat. A simple way is to put a length of hard tubing, and fill it with Oil. The short duration of the burn won't carbonize the oil in the entire length, so you should be safe.

Temps in a Ammonium Perchlorate motor are closer to 3000K.

HattoriHanzo
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Re: re: Rcandy Aerospike

Post by HattoriHanzo » Fri Jan 13, 2006 7:14 pm

Ray wrote:you'll have to protect if from the heat. A simple way is to put a length of hard tubing, and fill it with Oil. The short duration of the burn won't carbonize the oil in the entire length, so you should be safe.

Temps in a Ammonium Perchlorate motor are closer to 3000K.
Thanks for the tip.

I was thinking of low performance sugar/KNO3 fuel. It will burn with T=1400K or something like that. I am intend to build a small "candy" rocket engine during this year :)
A cheap pressure transducer would be welcome.
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re: Rcandy Aerospike

Post by MJD » Fri Jan 13, 2006 8:07 pm

A very effective way to mount a prssure transudcer is to use Swagelok compression adapters and a short length of 1/8" or 3/16" ss tubing. Fill the assembly from the pressure transducer to the end of the tube with high viscosity silicone fluid or silicone vacuum grease. Every so many firings, you will have to remove the tube and clean the gunk out then repack. Minor job though.[/quote]

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