Sugar rocket testing

Discussion in 'Beginners & Educational Programs' started by Tlaltecuhtli, Nov 7, 2019.

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  1. Nov 7, 2019 #1

    Tlaltecuhtli

    Tlaltecuhtli

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    Hello,


    I am new to Rocket design, I have a rough background in the science but no experience whatsoever when it comes to designing, building and testing.

    I have all I need to make some small scale (3/4 inch diameter, have not defined my length yet) KNO3-Sugar rockets with PVC casing, but I don't know how to go about safely testing the rocket. My only idea so far is to fill a bucket with dirt and place the rocket with exhaust facing upwards, will this suffice or do I need a more sophisticated test rig?

    Any thoughts / opinions are appreciated, Thank you!
     
  2. Nov 7, 2019 #2

    heada

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    If you're looking for a pass/fail type test, then that method is fairly simple and should work fine. I've done it up to 75mm diameter M motors. If you want to get valuable data from the test, such as a thrust curve, you need to build a test stand with a load cell and data logging. There are several examples around the internet. It can be as simple as a camera pointed at an analog bathroom scale.

    Making your own motors is considered research here. Discussion of formulas and methods is restricted to the research section of the forum. In order to join that section, you need to be in the US, at least 18 years old and at least level 1 certified. You haven't run afoul of any of the rules so far but it is common as people start discussing research motors.

    Lastly, you describe using PVC for the casing. If at all possible, find another casing material such as parallel wound paper, fiberglass or aluminum. PVC has the tendency to shatter when over pressurized which is the most common failure mode of research motors. Shattered PVC moving at high speed is a very bad thing for anyone nearby. Other materials are better because the don't shatter when over pressurized.
     
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  3. Nov 7, 2019 #3

    priitserk

    priitserk

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    1) Make electrical ignition system at least with 25 meters long wire (stay away, especially as you are using PVC) or use wireless ignition. Its very easy to make one. Just go to local electronics store and ask for resistance wire (https://en.wikipedia.org/wiki/Resistance_wire) They know what you talking about. If you connect it with 12 or even 9v battery, it will glow and ignite the propellant. Take max 3-4cm of this wire per ignitor, not more.
    2) Build a test stand. Use whatever strong material you can find - bricks, wood, etc ...
    3) Place a camera and record all the action.

    PVC is one awful material. Avoid if possible. Rockets are usually designed so that the cap will blow off in case of overpressure. Facing it directly in the dirt results in what? The casing will be pushed high in the air... I dont recommend that. Fix the entire rocket horisontally so that in the case of overpressure -> too fast burn speed = explosion, the cap or the casing will hit the test stand walls and no damage is done. You test rig/stand should be designed so that in case of explosion no harm is made and the casing fragments could not hit anyone. And try to keep at least min. 25 meters safety zone around the rocket in every direction.

    If you start testing you will quickly see that 99.9% you will be dealing with overpressure and casings getting blown up.

    Previous reply suggested to user fiberglass. Its even more awful than PVC... Aluminium is okey and stainless steel is even better. Fiberglass has same characteristics as PVC when blown up plus when burning fiberglass creates highly toxic fumes. If you have absolutely no idea what your doing use cardboard (paper casing like fireworks do)

    For data logging you can only use analog/mechanical scales. Digital scales have way too low response times, or super fast digital solutions but that are really complicated to make or expensive to buy.
     
    Last edited: Nov 7, 2019
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  4. Nov 7, 2019 #4

    K'Tesh

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    This is definitely verboten... You'll need to apply for the research section access before you can discuss this.
     
  5. Nov 7, 2019 #5

    timbucktoo

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    Only if formulas are given and as such, there are none.
     
  6. Nov 8, 2019 #6

    BABAR

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    Sorry, couldn’t resist this quote. Seems to me if you have “absolutely no idea what you are doing” than you should avoid doing ANYTHING that involves things that are flammable. Also avoid things that are sharp, things that involve heights, fast moving vehicles, electrical outlets, large bodies of water, and probably women.

    What you SHOULD do is FIND someone local who DOES know what they are doing and be nice to them and get some help before you hurt yourself or someone else.
     
  7. Nov 8, 2019 #7

    priitserk

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    Can't really agree. People have to experiment. I
    And telling a guy who wants to build a homemade rocket that go find someone who helps you is completely pointless. If you are a random guy then what is the probability that they know someone? Zero. This is the reason why they come to the forum and ASK for help. I find it utterly hypocritical that people start to count morals....
    I believe I gave sufficient information and safety instructions. If he has more questions, I do hope he replays to this topic or PMs. I am more than happy to share my experiences on CATOs and safety precautions that have to be taken before testing or launching any rocket or engine. I have several videos of CATOs and results of it. Experimenting is one of the reasons why I also suggest people to actually start to build their own motors. Then you actually know whats happening inside and what usually goes wrong. Factory built engines almost never fail and that creates false sense of security (they go bad time to time) and this is usually why people get hurt (applies 99% also to factory made fireworks)
     
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  8. Nov 8, 2019 #8

    PatD

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    Perhaps I am out of line, but may I suggest you read through ALL of these websites. They are a very thorough primer on sugar rocketry. Although there are others that contribute to the discussion, I think these are the most comprehensive sources of beginning sugar motor information. Pay attention to safety primarily, these things can bite. There is also information on inexpensive ways to test motors so you know what your creations are doing. :)
    https://www.nakka-rocketry.net/
    https://jamesyawn.net/
     
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  9. Nov 8, 2019 #9

    astronwolf

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    I believe that us old-timers, the one's who tend to join NAR and TRA, follow a safety code, and generally follow a model of the rocketry hobby that was created 60 years ago are out of step (substitute more colorful language here that you'd hear from me FTF).

    Do a search on "model rocket" on YouTube, and filter the results for "view count." On the filtered list I get, #5 is King of Random's (RIP) "How to Make Sugar Rockets" at 9.5 million views. I got asked about sugar rockets by young people who came to one of our "club launches" and they mentioned "King of Random." That's how I learned about this. This information is easily and widely available, and when young people look up "how to make a rocket" this is the information they get. You don't even need to get involved with TRA-EX to do this because to follow through with this activity, TRA is just an obstacle.

    Do a YouTube search on "how to make a rocket" to really get the propeller on your beanie spinning.

    The idea of a bunch of old curmudgeons sitting behind a forum firewall guarding their secret knowledge seems pretty silly. I'm not advocating a free-for-all amateur rocketry forum. The hobby, for me, is all about balsa and Estes black powder motors. But take a step back away from all of our cherished rules and notions and see what's out there. In my opinion, some of what I see makes us look pretty out-dated and silly.

    BTW, #2, and #3 in my search results are Dude Perfect videos that have 62M and 60M views and involve a form competition model rocketry. Competition and rocketry is something that seems to be anathema to many traditional old rocket fliers. Granted, Dude Perfect is a popular channel with many subscribers, but someone is watching and enjoying their rocket competition videos far, far more than what seem to be popular here. Just sayin...
     
  10. Nov 8, 2019 #10

    Arsenal78

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    If everyone found someone local to help them on everything, what’s the bloody point of this forum? Seems like you have something against research motors, or better yet, against people learning...
     
  11. Nov 8, 2019 #11

    SDramstad

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    No, we have a problem with people blowing themselves up.....and then calling what they are doing model rocketry
     
    Last edited: Nov 8, 2019
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  12. Nov 8, 2019 #12

    SDramstad

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    To the original poster, welcome! Model rocketry is a great hobby and you have found a great place for information. When you first start out you have to realize that right now, you dont know what you dont know. Getting on places like youtube and looking for rocketry will take you places you really dont want to go right away. Making your own motors is one of those places. I have been back in rocketry for 6 years now or so and am only now getting to the point of even considering making my own. Commercially made motors are easy to get and much more reliable then what you can scratch build. Build some rockets. Fly some rockets. Get to know people in person and online. Get an idea of what you are getting into. Then when you have a good foundation in rocketry, if you still want you can branch out into research motors or other more technical areas. One of the flags for us in your post was the PVC pipe. No matter what you see in youtube, we dont use it! It turns into shrapnel that wont show up on an xray....... You show up to a launch with something like that and you will not be allowed to use it. So what do you do now? Look through this forum. Many people have posed exactly this question before. The answers they got will help you. Find a local group. There are hundreds of them. Have some fun with us and then after you have mastered the basics, then you can expand into the more advanced areas of the hobby. Steve
     
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  13. Nov 8, 2019 #13

    BABAR

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    You have a point. I have nothing against learning. I do however draw the line at learning to do something dangerous to life, limb, or property (yours, someone else's, or both) solely based on information gathered primarily from online sources like forums and youtube videos. This is why NAR and Tripoli require supervision for high power motor certification, in fact Tripoli I believe assigns a personal mentor for the upper levels.

    Our new member is proposing something much more dangerous than an L1 cert. I have no problem with advice and support from forum members on his or her project, but such an endeavor in my opinion requires PERSONAL supervision, not just online advice. Again in my opinion we on the forum should not in any way support or encourage this poster UNLESS AND UNTIL we know he or she has some level of local EYES ON supervision. We can't replace that with forum posts.
     
  14. Nov 8, 2019 #14

    cwbullet

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    Although I slightly agree with you, there is a difference between watching someone doing it and reading it on the forum. I highly recommend a face to face mentor that can help you learn how to safely do this task.
     
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  15. Nov 8, 2019 #15

    Tlaltecuhtli

    Tlaltecuhtli

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    Appreciate the feedback! Thanks
     
  16. Nov 8, 2019 #16

    Tlaltecuhtli

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    Noted! Thank you, any suggestions or references to websites when it comes to building a safe test stand?
     
  17. Nov 8, 2019 #17

    jlabrasca

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    Since the OP seems to have gotten what they needed:

    >sigh<

    #okayboomer... >smile<

    The idea of restricting discussion of propellant formulas does seem a little silly in the face of all of the information that is exchanged in the open on other platforms, except for the signal it sends to the educable.

    There are going to be knuckleheads doing knuckle-headed things after watching other knuckleheads' "hey watch this" videos, but a few folks seem drift this way for information and advice on their way to the emergency room. This forum might be where they find out that there are alternatives to roll-your-own motors.

    This is not (only) idle speculation: At the club low power launches I have twice met younger-than-me folks who just did not know that you could buy rocket motors. One kid (late teens) showed up with a pretty nice rocket built from scratch that he wanted to fly on a home-brew motor. He was back a month later with lighter rocket and a pack of D12s (which he still couldn't fly on our field, but somebody gave him a C11 and he got in the air).

    At a different launch, a family with younger kids came just to watch. They were surprised to see all of the Estes motors. They expected us to be flying on motors made of >formula redacted< or >you do not have sufficient access< because that's what they'd seen on some YouTube channel, and it had not occurred to them to look farther than that.

    If you want an antidote to the depressing popularity of the Dudeperfect ninnies -- check out the view counts here

    https://www.youtube.com/user/numberphile/featured
     
    Last edited: Nov 9, 2019
  18. Nov 8, 2019 #18

    prfesser

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    There is an item available for purchase, consisting of pigments impregnated on dead trees, that (I've been told) is pretty useful when it comes to making and testing rocket motors... http://www.compositepropellantbook.com/

    YouTube videos on rocketry are free, and the majority are worth what you pay for them. The devil of it is that there's no way to tell which instruction set is worthwhile and which one is likely to give you a result that sits there smoldering, or CATOs, or worse.
     
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  19. Nov 9, 2019 #19

    rharshberger

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    I find the term #okayboomer (even with a smilie) just about as offensive as "murican", especially since its intended to be dismissive, offensive, condescending all at once it really has no place in civil discourse.

    For the record I am not a "boomer",but being somewhat polite was beat into me at an early age.

    As others have stated safety is the reason we recommend mentors. As for King of Random and that other group that had the HPR attempt to catch the rocket and blew one up on the pad intentionally, those while popular are negative impacts on the hobby even though they draw new fliers out, then we have to deal with people showing up at launches expecting these kind of crazy shenanigans and unsafe EX motors will be allowed to fly (yes it has happened, and getting more frequent, so far in the last year I have had to say no to people wanting to fly PVC cased sucrose motors).
     
    Last edited: Nov 9, 2019
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  20. Nov 9, 2019 #20

    astronwolf

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    I just dismissed it as a childish insult. It's kind of an overused corny term.
    I think the organized rocketry crowd has lost control of the narrative. Not sure that we ever had control of the narrative... maybe at one time... Yeah I can go on about safety, commercial motors... safe, sure, scientific in the whole pay it forward NAR mantra motto blah, blah, blah... I told a young man who came to observe that he can't fly sugar rockets with us, and he was not too perturbed. He just shrugged and told me he had another place to fly his creations with his friends. They don't need the local NAR/TRA clubs.
     
  21. Nov 9, 2019 #21

    cwbullet

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    Flying at a non-sanctioned event is fine until your rocket damages something. Accidents happen. I can't really say they are more common in private events, but I would rather have the backing of a national club.
     
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  22. Nov 9, 2019 #22

    Steve Shannon

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    As others have said, what you propose could certainly be done. You don’t even need the bucket; just bury the motor with just the nozzle pointing out. And, yes, there are prohibitions against using PVC as a motor case and they could affect you if you are too close when the case ruptures. Almost everyone who experiments with research motors (which is what we call homemade motors) has an occasional rupture.
    I’d like to interest you in learning the rules that keep us safe when testing and flying rocket motors, not just research motors, but commercial motors. They can be found at http://www.tripoli.org/SafetyCode. In your case you want to make sure you observe the safe distances, use electric ignition, don’t approach the motor for a period of time if it doesn’t immediately ignite, keep it pointing in a safe direction, and don’t insert the igniter until everything is buried.
    I’d also like to mention that Tripoli is a good way for people to learn about rocketry safely. Depending on where you are there may be a launch near you this weekend. There you’ll meet some of the friendliest people, have a chance to see how some people make and fly Research motors, learn about commercial motors, and see a safely run launch.
    You might learn about our high power certification levels. If you’re between 12 and 17 you might even be interested in participating in the Tripoli Mentoring Program (TMP). With a mentor who engages in Research motors a young participant in the TMP can actually participate in anything the mentor’s certification permits, including research activities.
    A map that show the location of Prefecture which may be near you can be found here: http://www.tripoli.org/Prefectures
    Zoom in on the part of the world that includes you and see what’s available. Good luck and be safe.
     
  23. Nov 11, 2019 at 10:31 PM #23

    High Desert Rocketry

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    I've tested 'sugar' motors in the ground for years...good way to test if you're doing something new and way different that could CATO and you don't want to risk load cells or pressure transducers and you don't have lots of money for something like NASA uses. The best way to test sugar motors is nozzle pointing down as that is how the motor will be oriented when launched in a rocket but that is often a problem properly securing the motor so it doesn't go flying off. If the forward bulkhead of your motor fails and blows off, that now open-end becomes the primary 'nozzle' and will try to propel the motor in the opposite direction. In the example of the nozzle up and unsecured in the ground, it will become airborne so motors need to be restrained from going in any direction.

    When they rolled out the X-15 back in 1959 I traded my dinosaur toys to start making rockets. No internet back in those days so we got our information from the library World Book encyclopedia. A few formulas and thousands of soda bottles later (we got our funds from collecting bottle deposits) we started blowing up our rockets, mostly because we were young and didn't know what we were doing. We were among the lucky that didn't get injured. NAR was new at that time and no help to us as they frowned on anything other than commercial Estes motors.

    Fast forward to today. You have so much information at your fingertips on the computer keyboard AND lots of help whether it's online or in-person with a mentor. My suggestion to all people new to rocket motor making, start small (as your 3/4" motor is) and find an experienced motor making mentor. Just because someone is a certified Level 2 or 3 doesn't make them a good mentor for making your own motors. The best place to start is at the nearest Tripoli Prefecture near you and talk with people and see if you can find someone willing to help you that has experience with motor making. Advantages? It will help you save time and expense with a lot of failed trials and errors and be safer.

    Here's a video showing one of our largest KNSB 'sugar' motors being static tested



    and a picture of our latest 6" sugar motor being tested. With 50+ years of experience I still manage to make a motor that doesn't work.

    DSC_0139 CATO 6 inch fiber glass 11 2 2019.jpg

    When doing any testing, distance and a barrier are your best friends...be safe so you can test again
     
    Last edited: Nov 12, 2019 at 8:10 AM
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