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Mile High Design

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Rocketmaniac

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I've come up with a "mile high" design I want to try....... It is based on parts that I have already........ I first went a "min diameter" design, but was worried about motor retention and wanted TTW fins......... So I went with a 2.56" body tube with a 38mm motor mount (close to min dia).......

With a Pro38 I285 she should get about 5900'......... If I add another 1.5 oz to the nose, I can fly her on a J350 and get about 6900' or an ellis J330 and get about 7800' (are the elllis J330 easily to find?)

See what you guys think? Did I make any hugn design flaws? (It is my first real design with rocksim)
 

Rocketmaniac

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Oh, I need to explain a couple of things about the design...... First the mass object in the nosecone is the adept altimeter and adapter to secure it to the nosecone shoulder (I guessed on total weight) Second the weight for the shock cord includes the shock cord, the nomex shield and two quicklinks........
 

edwardw

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Just looking at the file you didn't make the fins TTW. You can click on the tab and add them TTW so Rocksim will know that they are and calculate that in the CG.

Your launch lugs seem to be right in line with your fins so you couldn't put a rod through them.

Also, if you are using your altimeter for deployment most companies suggest about 2 body diameters away from the nose cone so that wierd things don't happen. For altitude reading I don't know if it affects what they read or not.

But, I like the design :) Keep us updated.

Edward
 

Ryan S.

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yeah, turbulance around the nosecone can cause premature deployment, also, dont forget the mach delay
 

teflonrocketry1

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Looks great!

I put the through the wall fins in and offset the launch lugs (12 degreees usually works). I also put the altimeter at the bottom of the parachute bay as Edward suggested. Make it a mach-buster; fly it on a Aerotech I284-W!

Good Luck,

Bruce S. Levison, NAR #69055
 

Rocketmaniac

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I guess I should have also said that the Adept altimeter is just for recording data, not dual deployment......... I was trying to keep down the final weight..... But I guess I could look at adding an electronics bay, and see if I still can break 5280'
 

edwardw

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Just to see if an E-bay would make it a non Mile High rocket I tossed an extra pound in the exact middle as a mass object. I did a quick sim with the I284 engine and I got 5800 feet. Max speed was 581 mph - not a mach buster but in the Mile High Club...oh wait the Mile High Club is something else :cool:
 

Rocketmaniac

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Originally posted by Rocketjunkie
I have one.
I should have guessed that you would have one of these beasts....... Will you be at the April launch? We will need to talk.....:D :D
 

Rocketmaniac

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Construction began this weekend....... Here is a pic of the motor tube and centering rings....... nothing fancy, actually the motor tube was taken out of an existing rocket that was junk (this explains the little centering ring right in the middle)
 

Rocketmaniac

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And here is the body tube slotted, ready for the fin can........
 

Justy

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Rocksim has a really nice tool, "Predict Optimal Mass" (under the Simulation menu). Run a simulation with the motor of your choice, then run this tool on it. It'll quickly re-run the simulation 20 times or so, trying to predict what mass your rocket would have to be to get the ideal altitude. I ran it with the first version of your rocket on the Pro38 J360 for example (I don't have the American market Pro38's loaded up... AFAIK the J350 is a J360 with the grains shaved down to meet the 62.5g rule). Your original rocket massed 952g and hit 7866' in calm winds. Bring it up to 1412g and it goes 400' higher.

On the I240, it's already bang on the ideal mass.
 

Rocketmaniac

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Originally posted by Justy
Rocksim has a really nice tool, "Predict Optimal Mass" (under the Simulation menu).

On the I240, it's already bang on the ideal mass.
I just ran this feature on the current version of this design...... Current weight is 32.5 oz, but the optimal mass is 41.5 oz....... 9 oz...... Now do you make this 9 oz part of the rocket (ie nose weight) or is it part of the motor weight? If it is additional weight added to the rocket, where do you add it? nosecone, middle section or aft end?
 

teflonrocketry1

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I would put the added mass in the nosecone since the stability margin on this rocket is close to one caliber by the Barrowman equations and close to two by RockSim. Putting 9oz of weight (lead shot and epoxy) into the nose cone brings the stability margin up to about 2.5 using Barrowman equations and 3.5 using RockSim, this also adds about 120 more feet of altitude. The maximum velocity also gets lowered by over 100 mph with the added weight.

The optimal mass prediction has to be run with a motor in the rocket and is based on a flight simulation that was run with that motor; the 9oz is weight in addition to the motor.

Bruce S. Levison, NAR #69055
 
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