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Impossible apogees

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Eduardo

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Hello everybody,
I participated in a virtual rocket competition, made with Open Rocket, that had the following rules:
- Motor E9 from Estes,
- Minimum mass: 200 g,
- Estability between 1 and 3 cal,
- Launch conditions: International Standart Atmosphere at 0 m,
- No physics law can be broken;
The target is to obtain the maximum apogee as possible.
I am really surprised that the winner has reached 800 m!!
I tryied to get the same result, but I had to break almost all rules and construct a "motor engine" for this result. The archive .ork is following.
Following all the rules, I really really really couldn't reach anything even near this result.
Is she hacking? Is there some way to make this project? How could I say this to the comission?
 

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Eduardo

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Something very important I've forgotten:
There must be a compartment with 20 cm lenght and 5 cm diameter!
The compartment can be empty.
This detail makes the apogee such an impossible number!
 

Louis Wu

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Hello Eduardo,
I‘ll check your file in a little bit, but wanted to comment on the idea of a virtual rocket contest (even if it’s just a design contest). I read about one conducted in 2010 (in Belgrade, I think) and sparked my interest. I think I’ll run one in our local club.
Regards,
Luis
 

Eduardo

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I think it's a great idea to run a competition into our comunity.
The winner file isn't avaiable. Althought, she had to follow all rules I described (includind such a compartment of 5 cm diameter) and got a result near to a motor with an ogive and a transition (and modified masses and CG's).
 

Louis Wu

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If it was hacked, it went past the judges and engineers reviewing and ’flying’ the entries. Could it be a misunderstanding in the parameters, or the results? I can see 800 ft, but I assume metric was required? I could try it and see what I come up with. Is there a list of competitors and their results? What was second place?
 

Eduardo

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As we're in latin america, metric system. The winner has reached 800 m.
There were no list of competitors and results, unhappily. It was a national competition but just the winner name and the number were told.
 

kuririn

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I believe it's possible.
Here's an out of production model that can, according to the description, exceed 2700 ft. (823 m.) on an E motor:
No 50mm compartment, but if you build ultra light and sacrifice durability it may be possible.
Paper instead of cardboard tubes, hollow foam or paper nose cone, no recovery gear.
In other words a one and done flight.
Maybe airfoiled elliptical fins to maximize apogee.
A tailcone will also improve aerodynamics. Maybe cardstock.
Minimizing weight and aerodynamic drag will maximize apogee.
(Although there is an optimal weight, too light and it will not have enough momentum to coast to maximum apogee).
 
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kuririn

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PS forgot to add if you eliminate a glued on launch lug you can increase apogee due to less drag.
Pop lug, piston launcher or tower launcher will guide the rocket for the first few feet without the extra drag during flight.
 

neil_w

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With a few mods to your file I added another 1000':
1603652585129.png

That is *almost* a realistic rocket. Fins are 1/16" and airfoiled, finish is set to "polished" for all components. Nose cone mass override removed.

I didn't put in the payload section, just wanted to show that your little "flying motor" was nowhere near optimum.
 

JoePfeiffer

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Is that min mass just the rocket (ie no motor) or on the pad?
Any recovery system requirements?
 

CoachSteve

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the mass needs to be 200g - the file above is only 97.6
The stability also needs to be over 1 cal according to the OPs opening problem :)
 

neil_w

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the mass needs to be 200g - the file above is only 97.6
The stability also needs to be over 1 cal according to the OPs opening problem :)
I forgot about the mass requirement in my model, whoops.
 

HHaase

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I've got to admit..... that contest looks fun!

-Hans
 

JoePfeiffer

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It does... I can think of some additional rules we'd want: most important is no mass and CG overrides! Also want to set a max velocity at parachute deployment (haven't gotten an answer back on the question of whether recovery is required; I'd think we'd want it to be) and max ground hit velocity...
 

ihbarddx

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Haven't looked at any data, here, but one possibility is a spike in the altimeter data from ejection shock. If you get one of these in an apogee-only instrument, the kick can add about 100 erroneous meters to the reported apogee. Naturally, the spikes are easy to see in data from recording instruments.

(And yes. Sometimes you get negative spikes, and sometimes those negative spikes result from leakage of ejection gas into the avionics bay. Those don't interfere with correct apogee reporting by apogee-only instruments. Spikes from shock can occur in positive or negative directions. The positive ones are the problem. I'm told good instruments can detect these and filter them out. IDK...)
 

CoachSteve

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so - back to the root of this thread - has anyone got even close to the claimed winning design?
Motor E9 from Estes,
- Minimum mass: 200 g,
- Estability between 1 and 3 cal,
There must be a compartment with 20 cm length and 5 cm diameter
- Launch conditions: International Standard Atmosphere at 0 m,
- No physics law can be broken;
800 m!!

I feel like someone cheated here - 5CM diameter for at least 20CM + the space for the motor cannot be in that area and 200g - an Estes E cannot do this - can it?
 

GalantVR41062

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Based on how I would interpret the rules you laid out my short answer is a hard no, 800m is not possible.

Put the Estes E9 in the payload even a spent e9 motor case might fit the bill. Then load up a real motor and send it, Estes/AT G40w should get it there.

The 24mm F32t or F35w would fall short on the 800m sim. I would also fill a balloon with helium that fills the entire payload bay/nose cone minus the E9/ spent e9 case.

Piston launcher using some crazy design and high pressure gas to get the rocket going faster then the E9 would ever push it, then air start the E9 with onboard flight computer and Ematch.

I took a rocket I had a OR file for and modified it to the 5cm x 20cm payload then down to a BT60 body tube with tailcone and 24mm mmt. I think the all up weight with the E9 was between 7-8oz. Sim shows peak altitude of 1300 some feet. Which I have flown a scratch built Bt55 rocket to 1350' on a Estes E12 but it was not optimized.

Then like Neil-w I designed a small optimized rocket putting aside the body dimensions, weight, etc and had a similar outcome.

~John
 
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