Can someone explain what IS happening to this first rocket?

Discussion in 'Beginners & Educational Programs' started by rickster75, Jan 11, 2020.

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  1. Jan 15, 2020 #31

    Steve Shannon

    Steve Shannon

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    I’m not addressing the unstable flight; things like that should not happen but they do. That doesn’t mean we think it is acceptable, but it was absolutely not indicative of the safety awareness at the launch.
    Safe launch distances were observed at all times. Anytime you see a launch video it has almost certainly been taken from the flight line using a long lens which makes distances appear very compressed. That’s what you’re seeing. This was a very well laid out and managed range at LDRS 37. TCC did a good job.
     
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  2. Jan 15, 2020 #32

    ThirstyBarbarian

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    I agree Steve. They run a good launch. The pinwheel flight was at LDRS 37, which was really well done, and the one in the original post was a year before that. The club observes all safety rules and is well organized. And yes, there was no one standing too close to the pads, and it only looks that way due to an optical illusion caused by the cameras.

    I wish the rocketeer would ask to fly his more ambitious flights further away, or someone would ask that he do so. The cluster flight of J and F motors was flown at a proper distance per the Tripoli rules for complex flights of that impulse. But looking at the setup, you could tell it had a good chance of going awry, hence the jokes about it being a bad idea and “duck”. And I think he had tried a similar setup once before that also crashed. It seems like that’s the kind of thing that should get a bit of extra margin. I enjoy watching his flights, but they make me nervous.
     
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  3. Jan 15, 2020 #33

    Steve Shannon

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    I completely agree.
     
  4. Jan 15, 2020 #34

    heada

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    The safety minimums are just that, minimums. There is nothing stopping the RSO/LCO from putting such rockets farther away. In times past when I was acting as RSO for our club launches, I asked that a rocket fly farther away than the minimums require.

    RE the cluster pinwheel flight: I wasn't there, I don't know the club or the flyer.... but why was it allowed to fly if it was known that it had such a high chance of failure?
     
  5. Jan 15, 2020 #35

    Steve Shannon

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    That’s exactly how such things should be handled: move them out if they present additional risk; prohibit them if they are most likely to fail.
    I don’t know what the RSO and his/her staff’s discussion was pre-pinwheel. I think the board was meeting when it happened and we heard about it afterwards.
     
  6. Jan 15, 2020 #36

    John Taylor

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    This kind of thing should never happen. When it does it should be throughly investigated. If it happens to the same flyer a second time it should be a big red flag. Allowing a flyer to fly a flight that requires the statement "duck" should tell you something needs to be changed.
    We have to protect our hobby and everyone involved as a whole. The potential for injury or worse from this Flier is readily apparent.
    Why is this allowed to continue?
     
  7. Jan 15, 2020 #37

    ThirstyBarbarian

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    I don’t know anything about the decision process or whether there was a discussion afterward about changes going forward. The club is generally safe and responsible.

    Personally, I’d love to see one of these “pod” style outboard flights work. They fail due to non-simultaneous ignition, and the wide distance between motors. I’d like to build something similar and airstart the pods after the rocket is up to speed and moving away, which I think would be much safer.
     
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  8. Jan 16, 2020 #38

    Woody's Workshop

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    Looks like a theme for a new Reality TV Series....
    Rich Kids Gone Rocket Wild
    With this kind of publicity (no matter how much he donates) revoke his HP Cert so he can't buy anything that dangerous.
    Too many points and you loose your drivers license, kind of thing.
     
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  9. Jan 16, 2020 #39

    Steve Shannon

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    I understand the righteous indignation that occurs when a person finds a video on the internet that shows an exception to the safe flights in our hobby, but please consider this:
    These events happened 1.5 and 2.5 years ago. At the time I’m sure they were discussed at length by the local club and lessons were learned.
    We’re not going to start retroactively punishing people who almost certainly already learned from their mistakes.
    There will never be no incidents; people are always trying different things. If you truly want these things to never happen we will have to limit flights to 10:1 fineness, 3 fnc, single motor mount, single stage, only rockets which have previously flown and only by those who have never had a flight do something unexpected, which is nearly nobody.
    If you really don’t want the public to see these videos for fear of what it might mean to the hobby, don’t post them over and over. Or don’t keep commenting; don’t keep driving them into the feed.
    Or better learn from them for when you host a launch with 300 flyers and 600 flights.
     
  10. Jan 16, 2020 #40

    astronwolf

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    This is a discussion forum, and it doesn't matter that the incident happened a couple years ago and has already been "discussed at length by the local club." Did the local club make public the results of their inquiry and analysis of this incident? Most of the rocketry community was not there and never had the opportunity to discuss this incident "at length." So they will and should be allowed to discuss it as much as it pleases them to do so. And several years from now, it may be discussed again. I support the current discussion and will always support open discussion about any incident.
    That cat jumped out of the bag a long time ago. Anyone can spend an evening watching YouTube video after video of high power rocketry mishaps. So "not driving them into the feed" seems sort of pointless. Consider that anyone can be watching those videos "out in the wild" without any discussion or context. So I support any discussion of any incident, and I believe that discussion should be "at length," or even, "ad nauseam." Circling the wagons and keeping our mouths shut is in my opinion, the wrong approach.
     
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  11. Jan 16, 2020 #41

    DAllen

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    Astron...I think you missed this statement. I don't think anywhere in Steve's post he is saying we should not discuss these incidents. I think he is addressing post 36 where the insinuation is that we ought to start punishing or banning people for bad flights with the question, "Why is this allowed to continue?" And also addressing the recommendation that a "full investigation" be completed when it almost certainly has already happened.
     
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  12. Jan 16, 2020 #42

    Steve Shannon

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    I think you misunderstood my post. I support discussing these incidents (ad nauseum) for the purposes of determining what went wrong and how to avoid it.
     
  13. Jan 16, 2020 #43

    mikec

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    FWIW, the same flyer flew what looks like the same Blackhawk 98 on a similarly-sized motor (M2100G) and it was stable though a bit wiggly.

    IMO, the outboard pod rocket just isn't a great idea. I had a four-motor cluster rocket (project written up in Sport Rocketry) that was plagued by similar failure to simultaneously ignite the motors, though the motors were not so far outboard. Clusters should probably always be flown with caution; obviously they are always "complex" so they get extra distance, but even more can't hurt.
     
  14. Jan 16, 2020 #44

    Steve Shannon

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    Right! Outboards have way too much control authority unless they are low thrust, decorative only, with a high thrust central motor.
    Now it might be possible to devise a pad release mechanism that holds a rocket down unless all outboard motors light.
     
  15. Jan 16, 2020 #45

    Charles_McG

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    So, could 1 BPS Signal board control three vector mounts in parallel? Or would it require three whole vector control systems? :)
     
  16. Jan 16, 2020 #46

    Steve Shannon

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    Although my undergrad engineering degree specialty was in controls, most of my experience the last 25 years was in other things. So, take what i say with a huge grain of salt.
    I think I would try it in parallel first. Separate systems would possibly fight each other. However, the algorithms Joe uses probably don’t account for off axis thrust so it might not even work if a motor doesn’t fire.
     
  17. Jan 16, 2020 #47

    innkeeper

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    Isn't that what the RSO is for, though?
     
  18. Jan 16, 2020 #48

    Steve Shannon

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    Yes, and the wealth of the rocketeer should have nothing to do with the decision to allow a rocket to fly. Other than speculation here I’ve never heard that it did.
     
  19. Jan 16, 2020 #49

    ThirstyBarbarian

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    I doubt seriously that wealth had anything to do with it. My only reason for bringing up the fact he is a venture capitalist is that it might have something to what seems to me like a high-risk, high-reward approach to rocketry -- it's the same approach to business that venture capitalists use, so he may be used to that way of thinking. But honestly, I've never spoken to him about it, so it was totally unfair of me to speculate on how he thinks, and I regret even bringing it up now. And I also regret posting the pinwheel video now that I see where the discussion has gone.

    The club runs a safe launch. They have adapted to and complied with changing rules regarding complex flights. I'm not sure what the decision process was for this flight and what was decided later based on any analysis that might have occurred after the fact, but I never really expected to hear public results of an inquiry. It makes sense to me that the club would not necessarily make any big announcement about a new policy for these kinds of flights and instead, if you walked up to the RSO table with this rocket today, they would just assign it to a further pad based on a new policy without fanfare.
     
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  20. Jan 16, 2020 #50

    DAllen

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    Many many moons ago I helped with a 20' tall 12" project that had a central M and three L motors. The concern was that the M would take much longer to come to pressure than the Ls so a device was rigged on the pad so that once the rocket moved a rocker switch was depressed by one of the rail buttons and completed a 12v circuit out at the pad that lit the L's off of a car battery. Now before anyone says anything I am fairly certain that method violates a few now standing rules that were probably not in place way back when. I was but a young rocketry padewan then and was yet not wise to the ways of the TRA rules.

    I think the outboard situation we're discussing here could be handled much in the same way - but much safer (notice I said safER). I think this is a good application for a PF timer, Raven or a ET Neutron I think its called. Just light the central motor and either the timer or flight computer detects launch and then proceeds to light the outboards ASAP with a very hot initiator. Size the central motor so that if the outboards do not light it will lift everything high enough for a safe flight and if only one lights it might be going fast enough to not alter the trajectory too horribly.
     
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  21. Jan 16, 2020 #51

    RocketRev

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    OK, just for the fun of it, let's get back to the original question, "Can someone explain what it happening with this rocket?"

    It is possible that the combination of an off-center/canted nose cone and an off-center/canted thrust vector could very well have caused the skywriting seen in this video. I had a buddy convince me to fly two of his 29mm "research" motors as outboards in a heavily modified, dual deployment, LOC-IROC that I built in the middle 90's and flew very regularly till just a couple of years ago. Clearly his motor skills needed some maturing. The central motor was a 38mm Aerotech J-570. But the flight was seriously canted off vertical. The high speed pics that I have clearly show that one of the outboards burned in about 1 second while the other outboard burned about like a road-flare. The flame and smoke characteristics of the two outboard motors were also completely different. The rocket did safely recover, but it was a close thing. Well over 3 dozen single motor flights in this rocket after that flight without any mishaps.

    It is also possible that something let loose inside the air-frame causing the rapid regression, minimalization, if not negation and or even reversal of the CP to CG ratio which could very easily have caused the sky-writing to take place. Yeah, been there done that at the last Kansas LDRS. Oddly enough with the same LOC-IROC. Unfortunately its last flight. I flew it in motor-ejection of recovery system mode and I think that the whole recovery harness scooted back under the very high thrust motor causing CP/CG negation and it went suddenly about 110 degrees sideways about 100 feet off the pad and then straight into the ground. Its the best explanation I've heard that fits the results of the flight. I still don't like it, but what other explanation is there?

    And it is also possible that a combination of the two caused the sky-writing effects that we see in the video.

    Unfortunately, there are just too many other questions that need answers before we can come up with any kind of definitive explanation as to "what happened" to the rocket in the video. Several possibilities have been noted. Watching frame by frame, it certainly does appear that the nose cone/coupler is not seated in a manner that most of us would consider "all the way" into the air-frame. I've RSO'd rockets and passed them without the nose cone being in the air-frame at all, just hanging there on the recovery harness. So I would give the RSO a pass on the nose cone unless we suddenly learn a whole lot more. Now, if it flew that way, I'd be talking with the Pad-Manager as well as the flier. Off center-thrust vectoring rocket in a single motor? I've not flown or handled the M-1075 Dark Matter motor. Does anybody know if this motor uses one of Aerotech's Medusa nozzles? The reason that I ask is because the Medusa nozzle is an up to 7 opening variable geometry nozzle designed to allow for using the same nozzle on various different thrust characterized motors/propellants by varying the number of nozzles that are drilled open. If the multiple nozzles were not drilled correctly or one side plugged early this could also cause the off center thrust vector seen in the video.

    Another possible explanation is that the rocket lost a fin going up. Did anybody here see the rocket after the flight? Were all the fins intact? Just wondering.

    Well that's all the speculation that I have for now, but I'd really like to know about the design of the nozzle on the M-1075 Dark Matter motor: Medusa or standard single throat?

    Brad
     
  22. Jan 17, 2020 #52

    Steve Shannon

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    You’re right, Brad. Sliding mass of parachute within the rocket is possible. Of course it’s easy to say later that all chutes should be slid aft-ward as much as possible before checking CG.
    Often a person doesn’t put shear pins in before the preflight inspection because the inspector may ask to see how your shock cords are anchored.
    I have had styrene shear pins shear due to the resilience of a tight chute before, but usually only half an inch or so.
     
  23. Jan 17, 2020 #53

    mikec

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  24. Jan 17, 2020 #54

    gldknght

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    If there was a guy around here that did something like this more than once, I would not allow him to fly with us, period! Way too much risk. We clear the area around our launch pad of flammable materials per the safety codes, but no way we can clear that much area.
     
    Last edited: Jan 17, 2020
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  25. Jan 17, 2020 #55

    samb

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    If it please the court I ask that this session of the He-man Steve Jurvetson Haters Club be adjourned. I hope some of y'all get a chance to RSO at a big high power launch. Sometimes the best laid plans ...
     
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  26. Jan 17, 2020 #56

    Uncle Toby

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    I agree. I am in no position to pass judgement on a flyer based on less than a minute of video.
    That said, let us address the wider issue of our public relations with the outside world. The journalist in me believes we should stop this endless defensiveness about the sport we love. It doesn't make us look good. In fact, it makes us look as if we have something to hide. So yes, let the YT videos roll. It's better advertising for us than it is an indictment.
    Finally, in defense of the flyer whose machine started this thread, I say this: Take no chances, make no advances. Maybe doesn't specifically apply here, but it certainly applies in general to rocketry.
     
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  27. Jan 17, 2020 #57

    Steve Shannon

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    Well said. And for those who are interested, Steve Jurvetson has an excellent TED Talk on Rocketry:
     
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  28. Jan 18, 2020 #58

    RocketRev

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    Steve S, thanks for the video. Delightful. Whatever else you might think about Steve J, his "joy of rockets" video is evangelism for rocketry. Yes, it shows a lot of catastrophes, but they do make for great photography. But it takes those willing to practice enough to get good at getting those very difficult shots. I just re-posted the video on my own Facebook page for those who may not "get it" about this hobby of ours.

    And thanks MikeC for info on the M-1075 Dark Matter nozzle. I usually learn more by asking questions and listening to the answers than about any other way. But hey, that just me. This is not original with me, but God gave us one mouth, but TWO ears! Maybe we should listen more than we talk. And I say that as a pastor who preaches almost every Sunday.

    Brad
     
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