Deepest crater competition

Discussion in 'High Power Rocketry (HPR)' started by ArchitectOfSeven, Nov 18, 2018.

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  1. Nov 18, 2018 #1

    ArchitectOfSeven

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    Disclaimer: Please DO NOT try to make things crash or intentionally make craters! This crash was dangerous as hell and it was terrifying realizing that even the launch site's hardened bunkers would probably not have been enough to protect us from this. That said,...

    Just for kicks, what is the biggest crater you've ever made in HPR? A student group trying to send a two-stage monster to 170kft at FAR yesterday might have just taken the record and made a permanent scar in the desert to boot. Post pictures if you have them! IMG_0222.jpg
     
    Last edited: Nov 18, 2018
  2. Nov 18, 2018 #2

    ArchitectOfSeven

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    A little information on the rocket:
    Booster: minimum diameter 98mm solid.
    Sustainer: same as booster I think.

    It was made out of what looked like filament wound FG tubes and nose cone. Fin cans were carbon fiber. The whole thing was beautifully made as far as I could tell so there wasn't really an obvious failure mode that could be predicted before launch except for the usual things that kill multi-stage attempts. Boost phase went fine(ish) but it appeared to light the sustainer at a kind of sharp angle and for some reason made a full arcing u-turn, winding up heading straight down while under power(at least it looked like it). After burn out it probably took all of 5-10 seconds to find the ground and sent up a huge dust and smoke cloud, implying that it was carrying some fuel on impact which somehow detonated. The shockwave from the explosion was loud and easily felt from a few miles away.
     
  3. Nov 18, 2018 #3

    Wallace

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    A properly designed bunker should have at the very least alleviated that. Pretty scary...
     
  4. Nov 18, 2018 #4

    cwbullet

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    "Explosion?" What caused that? I hope it was all from Kinetic energy.
     
  5. Nov 18, 2018 #5

    rharshberger

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    Could be it was the airframe collapsing and the air pressure causing the "explosion", we recently had a scale recovery of a 7.5" V2, when the nose cone impacted the compression of the air inside the airframe ejected the tailcone back to the full extension of the recovery harness.
     
  6. Nov 18, 2018 #6

    tfish

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    lipo batteries?

    Tony
     
  7. Nov 18, 2018 #7

    cwbullet

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    Good enough. I get nervous when we use the word explosion.
     
  8. Nov 18, 2018 #8

    jsdemar

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    I agree with the compressed air explanation. I've seen this many times. I saw a large (10" dia?) rocket power itself into the ground under a P motor. The crater was much larger than the one shown above. The nosecone acted as a piston into the fiberglass airframe. Kinetic energy converted to compressed air, then bursting the airframe.

    If the rocket has very little free space inside, such as all motor and propellant, there is no crater. Just a tiny hole with a buried rocket. This was the case with an unlit N-motor second stage coming down from 40K ft at Black Rock. A 4" hole with little marks where the fins went in. I happened to see the florescent paint mark around the hole. It was a couple of feet under the playa. Had to light the motor in place as the rocket's owner watched with a beer in his hand. ;-)
     
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  9. Nov 18, 2018 #9

    3stoogesrocketry

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    Hmmm aluminum shrapnel around the crater . Post impact burning , I'm guessing that is why the dirt is blackened? Seems to be more to this story then we know .
     
  10. Nov 18, 2018 #10

    ArchitectOfSeven

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    It made a lot of black smoke on impact and I think a bit of a flash, not just the displaced dirt and you can see the blackened dirt as well. One of the pyro-ops that saw the picture and heard the impact said it probably was a detonation of some unburned AP fuel although batteries could have contributed too. I saw it put together and armed and I didn't see any payloads or anything besides for plywood av-bay. The aluminum shard would be remains of the motor case most likely. Also it was predicted to have a top speed of like Mach 3.5 so lots of KE I'm sure.
     
  11. Nov 18, 2018 #11

    ArchitectOfSeven

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    They are about 6-10in of reinforced concrete with steel plate on the bottom but that was a hell of a big the hole...
     
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  12. Nov 18, 2018 #12

    eggplant

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    I thought the waiver at FAR was 50k?
     
  13. Nov 18, 2018 #13

    Nytrunner

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    Can "unburned AP fuel" actually detonate in extreme conditions? I thought the whole reason we won the ATF lawsuit was because it couldnt.....
     
  14. Nov 18, 2018 #14

    3stoogesrocketry

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    The only way this could happen , was if the motor was still under power as it plowed ground . This would cause the case to rupture , possibly producing the aluminum to shrapnel. But the OP said it was unpowered for about 10 seconds before impact.
     
  15. Nov 18, 2018 #15

    ArchitectOfSeven

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    They had obtained a special waiver for the launch. It usually is 50k.
    Well, it would react very quickly given enough pressure/compression but it doesn't achieve those conditions on its own in an uncontained state. No it isn't explosive but that doesn't mean much when it's in a high enough pressure and temperature environment.
     
  16. Nov 18, 2018 #16

    ArchitectOfSeven

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    Thats what it looked like, yet there was still a smoky cloud on impact. I was recording but the camera lost it at staging and after that I was way more concerned about everyone's safety then filming.
     
  17. Nov 18, 2018 #17

    rharshberger

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    The black on the ground could be from the soot products being ejected from the motor as it was destroyed in the "explosion", it would also create a cloud.
     
  18. Nov 18, 2018 #18

    grouch

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    None of this is cool and this thread needs to be closed. Seriously, the colleges are going to get our little hobby taken away from us one day.
     
  19. Nov 18, 2018 #19

    ArchitectOfSeven

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    Everything they did appeared to be by the book and there was no obvious lapse in attention to detail and safety. You have to know that a lot of people, not just college teams are interested in pushing the limits of hobby class rocketry and that always comes with risks. I'm sure this exact sort of thing has happened many times at BALLS and is exactly why big stuff is launched in unpopulated areas and with great attention to safety. Yeah it wasn't cool but it happened and is a stark reminder that HPR can involve tremendous amounts of energy.
     
  20. Nov 18, 2018 #20

    grouch

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    The people at Balls are generally smart enough not to air their dirty laundry to the world though.
     
  21. Nov 18, 2018 #21

    ArchitectOfSeven

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    It was a public access day. No NDAs were required and I thought some people here might find it interesting. Also I've never seen anything like it and wondered if others have had similar experiences.
     
  22. Nov 18, 2018 #22

    Steve Shannon

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    One of the papers I found while the lawsuit was in progress was a NASA report which documented their efforts to make solid rocket motors with APCP detonate in case they needed to self destruct. They couldn’t. They ended up adding HE to their motors.
    So when someone says APCP detonated, I’m skeptical. Are there additives that would support this? I don’t know, but simply repeating something like that is damaging to our hobby.
     
  23. Nov 18, 2018 #23

    hartlch

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    Maybe the impact set of whatever they were using for deployment charges.
     
  24. Nov 18, 2018 #24

    Steve Shannon

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    An unburned motor certainly could have catoed. My gripe is with the term “detonate”.
     
  25. Nov 18, 2018 #25

    ArchitectOfSeven

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    Fair enough. I just wonder what else you would call it if it rapidly combusted during the extreme compression period of impact?
     
  26. Nov 18, 2018 #26

    grouch

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    Rapid combustion and detonation are two different things.
     
  27. Nov 18, 2018 #27

    MattJL

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    Impressive crater... not impressive that it's coming from a university team, though. Really hope the size of the thing is a side effect of the soil or just a fluke, but the potential for bad PR is high.
     
  28. Nov 18, 2018 #28

    3stoogesrocketry

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    It is referred to a Deflagration.



     
  29. Nov 18, 2018 #29

    manixFan

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    I've seen plenty of very dangerous impacts of high powered model aircraft, including one where someone got hurt when they were clipped by a wing at high speed. Just because things like this happen doesn't mean someone is going to come take our hobby away from us. What grounds would they use? There are many far more dangerous hobbies out there that continue unabated even after serious safety incidents.

    Clearly we have to exercise all due caution but worrying that threads like these are going to get our hobby closed down seems like a gross over reaction.


    Tony
     
  30. Nov 18, 2018 #30

    cwbullet

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    I am going to ask this bluntly: what is the purpose of this thread? I agree we should watch the term explosion and detonate.
     
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