Standard AGM on an I200

[AKVP]

Hey all-

I am pretty sure I will be good but I wanted to throw this out there for opinions.

I got a standard Madcow AGM Pike. Building it light with wood glue etc. Total weight WITH motor should be under 6lbs. I planned this rocket for the 29mm I200-W with a Chute Release. It is for lower flights and a break from preping my larger projects loaded with electronics. Also I simply love the I200 motor.

I dont have Roc-Sim and open Roc sends my computer into a crazy mess. Looking at thrust curve for the I-200, if I go conservative and use the average thrust, the thrust to weight for the life if the burn is just a tad over 6:1. Plotting the thrust to weight from the actual time points would make it even better (at 0.25 seconds it is 10:1 and at 0.5 seconds it is 9:1). I just hope I get enough coast to get to 1000 feet.

Any thoughts? Has anyone flown this kit on an I200? I think this also would be for calmer days as there is a LOT of surface area on these fins.

Thanks
Andrew

 

[AKVP]

Here is the I-200 Thrust to weight.

 

[bobkrech]

You don't need a sim to answer your question.

The lift-off thrust of the I-200 is ~260 N. The weight of your rocket is 6 pounds x 4.45 N/pounds = 26.7 N. The Thrust to Weight ratio is 260N/26.7N = 9.7 G.

That's plenty for any rocket. The lift-off acceleration is a = (T/W-1) G = (9.7-1) = 8.7 G. Since 1 G = 32.17 ft/s^2, a = 32.17 ft/s^2/G x 1 G = 280 ft/s^2

To avoid severe weather-cocking the lift-off velocity should be 4 times the wind velocity. The leaving velocity is V ft/s = sqrt( 2 x a ft/s^2 x d ft) and by rearrangement d ft. = (v ft/s)^2 / (2 x a ft/s^2). Without showing a lot of math, you good to winds ~ 10 mph without severe weather-cocking with the I200.

(Short Cut Trick: a (G) = (T/W-1) = max wind speed (mph) is the recommendation for 6' launch rail)

Also simply use thrustcurve.org to scope out your rocket using the motor guide. 4" diameter, unloaded weight 5-6 pounds, 29 mm mmt x 15" long, cd ~0.8 will get you close. Apogee will be around 1100'-1200'.

Also for reference, I used Titebond II on a 7.5" WarLoc for my L2 cert rocket with a pad weight of 8 pounds with a J285. Absolutely plenty of strength.

https://www.rocketryforum.com/showt...ters-3D-Printing-Fun-lt&p=1576952#post1576952 photos and https://www.rocketryforum.com/showt...ters-3D-Printing-Fun-lt&p=1578729#post1578729 video thanks to Boris.

Bob.

 

[AKVP]

Thank you Bob-

This is some very good information. It is always good to get input from others. This was kind of like.....being at a launch and hearing somebody say "what do you think about this motor combination" for a particular rocket. Except I was not at a launch and wanted to see what folks would say on the forum.

Thanks again.
Andrew

 

[burkefj]

I'm sure it will do fine, I fly my 8" diameter foam rockets on the I-200, they are 5-5.5# and go to 1000 feet, but they are twice the diameter of your rocket so more draggy...my 10" diameter Atlas missile weighs 6.25# and goes to 750'.

Frank