My school's competition rocket..nose cone design

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Skiier08

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Our rocket must meet the following requirements:

carry one hens egg 850 feet, and return it to earth undamaged in a flight time of 45 seconds.


My bit of this project is to determine our best possible nose cone design. The factors that our leader wants me to take into consideration are:

1.Possible Shape

2. Properties of shape

3. Properties of length

4. Properties of the tip of the cone

5. Properties of drag


I would research these individually but i figure that you guys know from actually experience what works best and what does ot work what so ever. I would rather listen to the personal experiences that you guys have as opposed to some fact sheet.


So if it is possible tell me about what you think about each concept and give me a nice reply :)
 
Seems tough to design the nosecone in a vacuum, i.e., without considering the rocket as a whole. Unless of course the nosecone is of special function, e.g., the egg compartment, then you might start there.
 
Yeah i realize that there are things that cant be done until the other components are drawn up. I thought i could get some insight into pros and cons of different designs.
 
As with all Mod-Roc perfomance items you have basicly two things to consider: Dimensions: Diameter will likely be nearly a given as you'll have to fit the proper size egg..did the School at least give you a min and Max for whatever Grade Hens egg your going to be flying? Yes it makes a BIG difference.
Second is smoothness, this encludes seamlines, surface finish and transition taper.
Here a picture of a model I've won a B motor eggloft event or two with. That's not to say this is the form or function you folks need to follow but simply one approach. Motor impulse and dia are also very important to the design.
 
Subsonic flight?
Transonic?
Supersonic?

Very different things.

If you are working on a TARC entry, then perhaps what you should be asking for is what NC shape offers the most REPEATABLE characteristics. Does that mean minimum drag, to the point where any variations in NC design become negligible (compared to the rest of the rocket)?

I am not sure we are supposed to tell you what to do..... the TARC police may be watching.


Edit: there is a wee bit of data/advice posted at:
https://www.rocketryforum.com/showthread.php?threadid=29541&highlight=drag+coefficient
 
I've looked into being a TARC mentor and is almost certainly an entry for this year's TARC. From the mentor guidelines:

Encourage teams to use a rocketry flight simulation program (SpaceCAD or RockSIM) to verify the stability and likely performance of their model before its test flights. It is cheaper to crash a rocket on a computer than on the field!

and...

We ask that mentor volunteers (who do not have to be NAR members) do all that they can to encourage and support any team member or teacher sponsor who contacts them for advice...PLEASE do not design any team's official entry or help them in the building of it...

Soooo...Here's my first attempt at mentor advice - hold on to your panties, this could be wild. Do yourself a giant favor and spend the money on Rocksim. It's like $80 bucks or so and a huge time-saver especially when it comes to CP calculations. Just remember that this no substitute for real-world experience.

With Rocksim, you can change things like that and discover how big of a difference it really makes on the overall design. Personally, I don’t think you should spend too much time worrying about the shape pf the N/C. Find a N/C that is easy to replace and will allow for adequate protection of the egg and get on with the rest of the project. You have a lot of work to do.

Good luck!

-DAllen
 
Originally posted by DAllen
With Rocksim, you can change things like that and discover how big of a difference it really makes on the overall design. Personally, I don’t think you should spend too much time worrying about the shape pf the N/C. Find a N/C that is easy to replace and will allow for adequate protection of the egg and get on with the rest of the project. You have a lot of work to do.

-DAllen [/B]

Yeah. What he said.
 
As long as you are assured that you can make it to your target altitude, the NC shape is really not that important. (You may want to include a 5 or 10% margin just to make sure.)

You want to design so that drag is (relatively) minimal, which will reduce the performance variability due to drag. Drag (of the entire vehicle) should in most cases be on the order of a few percent of the effects of gravity; reduction of aero drag beyond that point is just not a practical place to spend your attention.
 
trying to pull one over on the TRF guys Skiier? ;) should have just said it was TARC... there *are* rocket scientists in here after all :p
 
Yes it is TARC boys i didnt want to give my competition any ideas :D . That one link provided was EXTREMELY helpful..thankyou teflonrocketry
 
Skiier, I think I speak for everyone at TRF that we'd love it if you would keep us up to date on what's happening with your project. Launch reports are good. Pictures are great. Obviously, you don't want to reveal too much. :D

And don't hesitate to pm me for advice or post questions here. Like the guidelines say, no one can design the rocket for you but we can give some general advice.

-DAllen
 
I am going to presume this bird has to be cooked from scratch. If this is the case, pm me and I will help you make a very nice nose cone that is also very light. The light weight is nice because you can then add weight to YOUR needs.
 
Originally posted by plasticpaul
If this is the case, pm me and I will help you make a very nice nose cone that is also very light.

Your comment, together with your TRF 'handle,' makes me wonder if you are in the business of fabricating custom plastic nose cones....
 
Yeah, i'm pretty sure it must be made from scratch..i think we can buy like body tubes and stuff we just cant buy a kit and assemble it. What would be the fun in taht anyways?
 
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