Deepest crater competition

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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
 
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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.
 

Wallace

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A properly designed bunker should have at the very least alleviated that. Pretty scary...
 

cwbullet

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"Explosion?" What caused that? I hope it was all from Kinetic energy.
 

rharshberger

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"Explosion?" What caused that? I hope it was all from Kinetic energy.
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.
 

cwbullet

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Good enough. I get nervous when we use the word explosion.
 

jsdemar

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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.
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. ;-)
 

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 .
 

ArchitectOfSeven

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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 .
lipo batteries?

Tony
"Explosion?" What caused that? I hope it was all from Kinetic energy.
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.
 

eggplant

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I thought the waiver at FAR was 50k?
 

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.....
 

3stoogesrocketry

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

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.
 

ArchitectOfSeven

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I thought the waiver at FAR was 50k?
They had obtained a special waiver for the launch. It usually is 50k.
Can "unburned AP fuel" actually detonate in extreme conditions? I thought the whole reason we won the ATF lawsuit was because it couldnt.....
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.
 

ArchitectOfSeven

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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.
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.
 

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.
 

ArchitectOfSeven

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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.
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.
 

ArchitectOfSeven

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The people at Balls are generally smart enough not to air their dirty laundry to the world though.
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.
 

Steve Shannon

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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.
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.
 

hartlch

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Maybe the impact set of whatever they were using for deployment charges.
 

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.
 

manixFan

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The people at Balls are generally smart enough not to air their dirty laundry to the world though.
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
 

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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