RSO Checklist?

Discussion in 'The Watering Hole' started by ThirstyBarbarian, Jun 22, 2019.

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  1. Jun 22, 2019 #1

    ThirstyBarbarian

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    Do you have a checklist of items that you use when inspecting and checking in rockets for pad assignments? Does your club use a formal list or have a formal training procedure? Does anyone know if NAR or Tripoli has anything official?

    I notice that the thoroughness and time spent on RSO inspections seems to vary a lot by club and from one individual RSO to the next, so I was wondering if there is a standard or set of guidelines or best practices.

    Thanks!
     
  2. Jun 22, 2019 #2

    Steve Shannon

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  3. Jun 22, 2019 #3

    rharshberger

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    NAR has a program for Trained Safety Officers.
     
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  4. Jun 22, 2019 #4

    lakeroadster

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    I created this in Excel. If you'd like a copy PM me your email address.

    Countdown Checklist Rev. 02.jpg
     
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  5. Jun 22, 2019 #5

    rharshberger

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    Our club has a quick list on the back of our flight cards that is filled out by the safety inspection officer, its not a comprehensive list but it hits important points like recovery installed, nose cone tension, motor retention, stability, fin structure/construction, first flight (all first flights are heads up flights, and just changing to a never before flown motor is reason for a new " first flight").
     
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  6. Jun 22, 2019 #6

    ThirstyBarbarian

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    Thanks! I was able to access the document without a login. This is great info.

    Thanks! I’ve been asked to volunteer more often for rocket check-in at club events. If I get more involved as a volunteer, I might check out the formal training.

    That is a very thorough checklist! I’ll PM you my email. Thanks!

    That’s a pretty good idea.
     
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  7. Jun 22, 2019 #7

    caraviator

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    I thought I saw a 3 page guide that some club crated of different things for RSO’s posted here on TRF, but I’ve not been able to find it again. Anyone else seen it?
     
  8. Jun 24, 2019 #8

    cbrarick

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    I hope it's not found. Call me a jerk if you must, but here's my (inflammatory) opinion:

    RSO's should be experienced enough to not need a checklist. If you're not, then you should be the ASSISTANT RSO.
    I'm not trying to be elitist at heart, just saying that it should be someone with true experience and certifications.
    Checklists only go so far. They can't take into account every possible rocket.

    I have seen some good RSO's realize the project is over their head, and go get help. That was really cool.

    The RSO shouldn't turn it into a interrogation, either. There are teachable moments, but we shouldn't shame the new people away. In my travels I've seen this, as well as a huge number of good RSO's. Unfortunately, the ones who stick in your head generally aren't the good ones.

    Remember it's Range SAFETY Officer NOT Rocket Success Officer. There's a difference. Sketchy rockets go to a pad far enough away that they won't come back to the flight line. It's up to the flyer to decide if he or she wants to walk that far and/or drag a pad with them........

    JMHO

    /Flame on/
     
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  9. Jun 24, 2019 #9

    jqavins

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    Yes, experience is the most important factor. Even the most experienced people can still slip up. That's why commercial and military pilots, surgeons, and lots of other highly skilled and experienced professionals use checklists.

    I'm grateful for the thread; thank you for starting it, Mr. Barbarian. (May I call you Thirsty?) and Steve and John for the responses. My club, like most I imagine, is always looking for volunteers, and I'd like to step up but don't feel competent or confident. A comprehensive checklist is not a substitute for experience at the table, but will be a great adjunct to it.
     
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  10. Jun 24, 2019 #10

    Bat-mite

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    While lakeroadster's checklist is very nice, I do not want to be asked 50+ questions when getting a rocket RSOed that I have flown many times with the same club in the same configuration.

    I'd start with, do you know the flier? Would you go through a 50 point checklist with Crazy Jim or John Coker?

    Next, have you flown this before with the same configuration? If so, how did it go?

    If you get a very young flier or someone you've never seen before, then a more exhaustive approach is needed.

    As an example, when I got RSOed on Saturday, the TAP made sure my shear pins were in, my retainer lid was on tight, my fins weren't loose, and my rail buttons were damaged or loose. Done.
     
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  11. Jun 24, 2019 #11

    jqavins

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    Whenever I'm RSOed, the RSO checks a bunch of stuff visually, and doesn't question me on every point. I have to assume that a checklist isn't a script, but a list to aid the RSO in being sure to remember to check all the things. And a useful (not the only) learning tool for new potential RSOs.

    Come to think of it, it's also a good aid to flyers, especially new ones. "Here's what the RSO will be looking for, and you should look for yourself on park launches. Have you covered all these bases?"
     
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  12. Jun 24, 2019 #12

    boatgeek

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    A lot of LR's questions are really related to field setup. The RSO doesn't know if the rods are bent, for example. It's great for the flier to check that, but I don't think that's the RSO's job. I have never seen the RSO open the rocket to check the chute. I'm pretty grateful for that, because that would mean re-packing the chute. In addition to the questions Bat-mite mentioned, I've been asked if the recovery system is installed and connected at both ends, a check of thrust to weight, and a fit check on the nose cone (obviously not needed if there are shear pins). For cert flights, it's pretty common to ask about CG/CP, as well as for any odd scratch builds.

    I'm interested in all first flights being a heads up flight and the first time using that particular motor being a first flight. That seems unusually strict to me, though it may be the easiest way to capture the difference between having a successful flight on a H133 Blue Streak and then wanting to fly a G33 Mellow.

    Our club also only RSOs motors G and above, so that may be different.
     
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  13. Jun 24, 2019 #13

    lakeroadster

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    The list I created is for the flyer. I used the checklist created by Timothy Van Milligan in his Model Rocket Design and Construction book as a guide.

    I don't fly at "events", so I created this list for myself to run through pre-launch, much of which can be done at home. That's why there are 3 columns... much of the data only needs to be checked once if the rocket will experience multiple flights in one day.
     
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  14. Jun 24, 2019 #14

    Bat-mite

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    Gotcha! I think it would be a great idea for clubs to have these available for fliers to grab and use if needed.
     
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  15. Jun 25, 2019 #15

    dr wogz

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    Having done some RSO work, my biggest gripe is too low of an impulse motor.

    Multiply the weight by 25 (or 17 or 20 for a really nice no wind day) that's what the impulse minimum should be.. The RSO table should have the safety margin charts or a calculator to do the math on hand.

    (I've seen a few ~1lb rockets on an Estes BP F15..)
     
  16. Jun 25, 2019 #16

    Nytrunner

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    Impulse or thrust?

    And what measure of weight?
     
  17. Jun 25, 2019 #17

    jqavins

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    Impulse (Ns, the letter) or thrust (N, the number)? Also, weight in ounces, I presume?

    (Oops, looks like Nytrunner was quicker on the trigger.)
     
  18. Jun 25, 2019 #18

    dr wogz

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    sorry, yes.. weight in lbs
    thrust Newtons (average thrust) yes, I should have said thrust, not impulse..

    So, multiply the weight (2lbs) by 25 to obtain the minimum average trust needed: 2 x 25 = 50. a motor with "50" after the letter would get it up safely..
     
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  19. Jun 25, 2019 #19

    Bat-mite

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    This is just the basic 5:1 ratio, but he is confusing average thrust with total impulse, I think. Weight is the total weight on the pad in pounds. Multiply by about 23 to get the minimum average thrust. So 6 lbs. requires 133 N of average thrust.

    Of course, we all know that average thrust is not a dependable measure, and it really comes down to speed off the rail in the first 1/4 second or so.
     
  20. Jun 25, 2019 #20

    Bat-mite

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    Sorry, crossed in the ether!
     
  21. Jun 25, 2019 #21

    Nytrunner

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    AH, now I have the understanding. Lbs to N (4.448) to 5x thrust/wgt is ~20
    That's an easy mental trick to use in a pinch. If the data is available, I prefer to use the 1st 1/4 second avg thrust.

    Speaking of available data, I really need to update my Lazy RSO's motor guide
     
  22. Jun 25, 2019 #22

    jqavins

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    OK, now here's a question that has long (but only occasionally) bugged me. All BP motors except the very small ones, and many APCP motors have much higher thrust averaged over the first 1/4 second or so than the thrust averaged over the full burn. So it follows that the 5:1 rule should only be applicable to one or the other period. We usually here the ratio applied to the thrust number in the motor designation, so the full burn time average. Doesn't that mean the ratio can be lower when only that early peak period is considered? 3:1? 2:1? I dunno.

    Of course, the right way to handle this is to calculate of simulate the speed off the guide as a function of guide length and weight, then determine the maximum safe weight for each motor. Oh, wait, the manufacturers do that and publish the maximum safe liftoff weights. So why use a rule of thumb when the answer is published?
     
  23. Jun 25, 2019 #23

    Nytrunner

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    Under what conditions is that the "Max liftoff" weight? Sometimes you can exceed that, sometimes you can't fly with that weight.
    Like most answers in rocketry, It Depends(TM), and the RSO is responsible for making the determination.

    Watched someone try and argue for 10 mins with an L3CC member because their draggy brick (not an oddroc, just a really ugly rocket) was "under the max liftoff weight" of the F22 and it should be allowed to fly right now (from the MP pads and during 10mph winds....)
     
  24. Jun 25, 2019 #24

    Bat-mite

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    Absolutely!

    Which is why thrustcurve.org is such a quick and handy tool for on-the-field calculations, and proof to an obstinate RSO.

    Because the 5:1 is easy to calculate without any knowledge of the motor characteristics, and the table can be printed as an easy guide to RSOs.

    Here is a couple of examples:

    upload_2019-6-25_11-57-49.png
    The Loki L930 gets you 1123 max thrust at the beginning, where you most need it. So that almost 200 N more than the average.

    The L780 spitfire only gets about 500 off the pad. So you lose 280 N when you most need it.

    upload_2019-6-25_12-1-8.png
     
  25. Jun 25, 2019 #25

    SDramstad

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    Then you have motors like aerotechs I59 with a peak thrust of over 35 lbsf and an average of around 13 lbsf. So either a 7 lb rocket or a 2.6 lb rocket......

    [​IMG]
     
    Last edited: Jun 25, 2019
  26. Jun 25, 2019 #26

    Scott Hala

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    As a returning rocket hobbyist, some of these items should be in my personal launch checklist.

    and if I might ask. Where can I get the graphs that SDramstad included?
     
  27. Jun 25, 2019 #27

    Nytrunner

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    Thrustcurve.org. !
     
  28. Jun 25, 2019 #28

    boatgeek

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    My understanding (and please correct me if I'm wrong*) is that motors with thrust curves like the Loki L780 are relatively rare. Motors with relatively constant thrust are pretty common, as are motors whose thrust tapers off in the burn. So for rules of thumb, using average thrust is conservative** in most cases for white, blue, red, and green. If your weight is close to the 5x thrust line, it would definitely be worth the RSO asking about it.

    * Thanks, Bat-mite for the corrections! A quick look at CTI 54mm motors as a representative sample shows that smoky and skidmark motors tend to have a short peak in thrust at ignition, followed by a dip, followed by rising through the burn.
    ** In the engineering sense, where error tends to give a safer result than your calculation.
     
    Last edited: Jun 25, 2019
  29. Jun 25, 2019 #29

    Bat-mite

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    It really depends on the propellant type. Sparkies and black smokey motors have lower initial thrust, while reds, whites and blues usually have a very high initial thrust.

    Greens are sort of flatlinish.
     
  30. Jun 25, 2019 #30

    jqavins

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    And BP motors nearly all look more or less like this:
    upload_2019-6-25_12-32-4.png
    For this particular motor (Estes C6) the average thrust is not 6 N but 4.74, while the average over the first 1/4 second is about 6.4 N (calculated from three eyeballed graph points, so pretty rough). That is only 1.35 times the average, and nearly the same as the '6' in the motor's name. So I've just disputed my own theory, at least where the C6 is concerned. If one uses the 1/4 second approximation for time to leave the rail, which is really rough.
     

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