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  1. #1
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    Nose Cone Shapes

    A college friend of mine is getting the Physics club to conduct an experiment about nose cone shape vs. height, and the effects associated with them. I know I've seen a link to a seller (fliskits?) that sells a variety of nose cone shapes to be used for this exact experiment. Does anybody have the information?

    Thanks

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  2. #2
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    The vendor you are looking for is Apogee Rockets, they have a science fair kit with nose cone assortments....

    G.D.

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  3. #3
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    Ah there we go. Thanks Gregg
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  4. #4
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    I didn't count, but I'd bet Semroc has the most options.
    Unstable by design
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  5. #5
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    Quote Originally Posted by chadrog View Post
    I didn't count, but I'd bet Semroc has the most options.
    Oh definitely , and probably cheaper, too.

  6. #6
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    Go into Open Rocket or some other sim program and model the different nose cones and see what kind of altitude differences you get. I'm afraid you might find that the altitude difference based on the nose cone shape is minor copmpared to the motor variability.
    Zeus-cat
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  7. #7
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    Quote Originally Posted by Zeus-cat View Post
    Go into Open Rocket or some other sim program and model the different nose cones and see what kind of altitude differences you get. I'm afraid you might find that the altitude difference based on the nose cone shape is minor copmpared to the motor variability.
    Oh I know, but a friend of mine was going to test nose cone material for drag, and I steered him away from that as an inch plus or minus won't be accurately measured.

    Shape will give at least a few feet with a C6, and it's a ready made kit that they can take to a local launch and test out in a day.

    I was just the unlucky rocketeer that everybody at my college knows flys rockets :P
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  8. #8
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    Quote Originally Posted by chadrog View Post
    I didn't count, but I'd bet Semroc has the most options.
    That's my impression. http://www.semroc.com/Store/Scripts/default.asp

    Plus, they have a wide variety in different sizes as well, in case they want to do this experiment on larger rockets.

  9. #9
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    The way to do this is in a wind tunnel...more accurate, far more controlled, much better data, and if they're launching C's, they're not going to be looking at any high velocities.

    Colleges can usually get into professional installations when they need to.

  10. #10
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    Quote Originally Posted by edwinshap1 View Post
    Oh I know, but a friend of mine was going to test nose cone material for drag, and I steered him away from that as an inch plus or minus won't be accurately measured.

    Shape will give at least a few feet with a C6, and it's a ready made kit that they can take to a local launch and test out in a day.

    I was just the unlucky rocketeer that everybody at my college knows flys rockets :P
    Even variation in nose cone shape is likely to be rather small - to properly do this experiment, some care will need to be taken. Weight will need to be carefully matched between nosecones, and a number of flights with a fairly high accuracy altimeter will need to be performed with each nose. My guess is that the variations in motor performance and launch conditions will make at least as significant of a difference as the change in drag from typical nose cone shapes.
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  11. #11
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    Quote Originally Posted by cjl View Post
    Even variation in nose cone shape is likely to be rather small - to properly do this experiment, some care will need to be taken. Weight will need to be carefully matched between nosecones, and a number of flights with a fairly high accuracy altimeter will need to be performed with each nose. My guess is that the variations in motor performance and launch conditions will make at least as significant of a difference as the change in drag from typical nose cone shapes.
    Exactly right; except I believe the motor variation and launch conditions will far exceed the nose cone variation. That said, the experiment could still be done, but the statisitcal analysis gets very,very complicated and you will need to do a lot of launches. Just off the top of my head I would guess you need to launch the same nose cone 20 or 30 times to minimize the effects of motor variation. And that assumes you can minimize the effects of temperature, humidity and air density. I am an engineer and have a Masters degree in statistics so I am not making this up. OK, it is a guess, but an edumcated one.
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  12. #12
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    So I thought about this a little more. You need to reduce the effect of all the uncontrollable variables.
    Here is what you need:

    1) A sturdy rocket that can be launched at least a dozen times without needing to be repaired even if it has a few hard landings. The recovery system needs to be simple, robust and repeatable (you can put the chute or streamer in the rocket the same way so that CG and weight are the same for each launch).

    2) Two nose cones that are different; the more different in shape the better. Label them A and B

    3) A good altimeter

    4) About 15 motors (maybe more) all the same size. Weigh them and keep the 12 that are the most similar. Pick a motor at random and label it #1. Repeat the procedure until all 12 have been labeled. Record their weights.

    5) Pick a calm day without a lot of temperature or barometric changes.

    6) Randomize your nose cone selection for each flight. This can be as easy as flipping a coin. If it comes up heads use nose cone A; tails then use nose cone B. You want a sequence something like ABABBABAABAB.

    7) Have the same person perform each step of the rocket prep for each flight. If Ralph packs the chute for flight #1, then he needs to do it the same way for all 12 flights.

    8) Prior to the flight record the weight of the rocket, the temperature, humidity, wind speed and direction, barometric pressure, etc.

    9) After the flight record the altitude.

    10) Repeat until you have completed all flights.

    11) If any flight had serious problems consider removing that piece of data from the test.

    12) Average the altitudes for the 6 flights for nose cone A. Do the same for nose cone B.

    By randomizing the motors and the nose cones you have reduced the effect of the unknown variables as much as possible. I think 6 motors for each nose is too small of a sample size to get serious results, but it makes the experiment practical and doable in a few hours.
    Zeus-cat
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    Flights: 98

  13. #13
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    this is probably more about the process than results...that said use a flat cylinder as one nose and an ogive for the other. that might produce a measurable difference at lpr speeds.
    rex

  14. #14
    Find Stine's book _Handbook of Model Rocketry_ . It has some information on different coefficients of drag for different nose cone shapes. But I agree with the advice to try different shapes in a simulation program.

  15. #15
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    Wind tunnel would be the ideal for this, if you can get one. If you can't....

    Thinking outside the box, this might be a good project that will save a lot of money in engines and may be more consistent.

    http://exploration.grc.nasa.gov/educ.../rktstomp.html

    has a generic air pressure launched rocket system. Basically can set this up like a piston system. What I am not sure of is if you can get a rapid pressure release system for launch. You can pump up to the same pressure for every launch, release, and measure either altitude or time of flight. I am thiiiiinnnnkiiiinnnng that these won't go very high, they would be very very light (only a nose cone, body tube, and fins) and could be featherweight recovery, reducing the variability in descent time. You will need a soft grassy field, as these will come in balistic. Put a bulkhead in behind the nose cone to hold the pressure, and you can use the same rocket body and just swap out nose cones. To make sure the greatest effect on drag is the nose cone, experiment with the minimum fin surface area required for stability (may not take very much fin area.) Given the low mass of the rocket, I suspect the drag will slow these down in a hurry.

    The thing I am not sure about is the pressure release valve, has to be able to nearly instantaneously release the stored pressure in the tank to the rocket to prevent variability. I am thinking you don't need a launch rod, you use a piece of metal pipe just less than the inside diameter of a BT-20 rocket and fit the rocket over the pipe. Max velocity will be reached at or before the rocket is off the pipe, if it isn't stable by then it is never going to be. Rather than a bike pump, 12V tire pumps are pretty easily available and cheap.
    You will need a tank and a pressure gauge and a rapid release valve.

    Advantage again is cost of engines and ease of flying flight after flight after flight.

    Addendum: Actually an easier measurement device would be (and again, safety considerations come into play here, this is NOT NAR safety code) to launch at an angle and measure distance traveled. NAR code restricts angle to 30 degrees, but I am not sure NAR code applies in this case. I believe 45 degrees gives you the best bang for your buck. Again caution adviced, these would be featherweight but the nose cones are kinda pointy.

    Last edited by BABAR; 18th November 2012 at 09:09 PM. Reason: thought of something else
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