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Appropiate Nose Cone material?

posted Nov 29, 2015 06:49:26 by Commander
In the current edition of the NAR's Sport Rocketry magazine (November/December 2015, Vol. 57, No. 6) is an advertisement. I have seen mention of a certain ad on another forum which said thread was concerned about the size of a particular rocket, but that is not the one that caught my attention.

There is an ad for a certain Black Brant II rocket kit which states the nose cone is Fiberglass Filament Wound, conical with an Aluminum Tip.

Aluminum Tip??? Am I the only one concerned about the effect that tip might have on human flesh? Is there no rule in high power rocketry against having structural parts made from metal?

Even if we hadn't just suffered a fatality in the rocketry world, I would have questioned this, but now it strikes me as reason for even greater concern. Far too many High Power people think that they are justified by the high cost of their rockets to use building techniques and materials to make their rockets like tanks.

If such building practices continue, I feel it should be made mandatory for the Organizations licensing these individuals to require a self destruct device be built into the rockets and the triggering key be given to the RSO.

Commander
Starport Sagitta
NAR No.97971
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7 replies
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luke-strawwalker said Dec 01, 2015 06:22:49
That's another reason that I don't want HPR activities within 5 miles of our farms, me, my family, or my property. I've seen too many times already the "hold my beer and watch this" mentality from HPR people and lots of other stupidity... so this doesn't surprise me one bit... yeah, I think the rule reads "no SUBSTANTIAL metal parts" but the thing is, when you get right down to it, most composite materials are stronger than steel (which is WAY stronger than aluminum!) and when you figure up the actual yield strength of the materials and joules of energy imparted for a given impact speed, and the PSI of pressure exerted and penetrating ability of certain shapes, regardless of what material it's impacting...

It's probably about time to start SERIOUSLY looking at these sorts of issues... most of the MRSC and HPRSC restrictions on materials date back to the "basement bomber" type days of the 50's (October Sky comes to mind) where kids were building rockets and motors out of steel pipes and such and were lobbing them indiscriminately into the sky, without recovery devices in many/most cases, and presenting a real possibility of skewering someone or something on the ground... or having home-made motors blowing up and sending white-hot shrapnel in all directions... It made perfect sense back then, to make a "no metals" rule (which stood quite firmly until reloadable motors came about, relying on metallic reusable casings to provide the backbone of the motor instead of a wound paper or expendable composite casing). At that point, the rules had to be 'relaxed' to allow for reloadable motors, with the understanding that the casings were designed to fail in a controlled manner (blowing off the end closures) rather than explosively rupturing and sending out shrapnel in the event of a motor cato.

I don't know when or where it became "acceptable" to use aluminum fins, fin cans, and nosecones. IMHO, AFAIC, it's NOT acceptable and never would be at any launch taking place on MY property... I've read stuff about these guys trying to launch minimum diameter rockets to multiple Mach 2 or better, and purporting that aluminum nosecones or fins are *required* for that application to resist the high aerodynamic heating at those speeds, etc... but I'm not sure that's legitimate, and at any rate, *I* for one would be saying, "that's all well and good, but you're NOT launching that HERE! Take it to one of those big desert launches so that if something goes wrong 1) there's plenty of NOTHING to land in, therefore less risk of perforating anyone else or anybody else's property, and 2) it's far away from ME (and the rest of the club, neighbors, etc. IMHO such "complex rockets" that *require* the use of metallic parts should be labeled "experimental" designs and have a higher risk/hazard associated with them than "standard" hobby rocketry kits/flights, and should be flown only at "experimental" launches conducted in venues sufficient to ensure the safety of those involved (usually due to remoteness).

Course, like I said, it's not just "substantial metallic" parts that pose a high risk, IMHO... I've seen regular "off the shelf" hard plastic ogive nosecones separate and impact and the results WOULD have been fatal had anyone been hit... and there's already been a LARGE number of near-misses, so really it's something of a miracle that we haven't already had a NUMBER of fatalities due to impacts from rockets... I once saw the remains of a large HPR plastic nosecone that separated at altitude and came in ballistic, overflying a crowd of several hundred and the parking lots behind us to land in the woods beyond-- it embedded itself about 6 inches in the ground, and the remaining 1-2 feet of nosecone length then turned "inside out" as it buckled and split... the only part of the cone that was intact and still had its paint was the first six inches back from the tip that had embedded itself into hard packed undisturbed clay soil and been supported by it during the impact-- it drove itself in that deep before the "yield strength" of the material was reached, and the rest of the impact energy went into buckling the heavy plastic, rolling it over onto itself, and splitting it near the shoulder area... Of course, the point is, IT EMBEDDED ITSELF INTO HARD SOIL SIX INCHES DEEP *BEFORE* THE YIELD STRENGTH WAS EXCEEDED; clearly the amount of energy imparted to the 'target' at impact was more than sufficient to kill a human being, or perforate straight through the sheet metal bodywork of a vehicle, house roof, etc... In this case, it was the SHAPE and the size/weight of the object (ogive nose cone) coupled with the material thickness and strength, and the energy from the altitude and velocity of the object at impact... Of course, had it been a "Big Bertha" shaped nosecone of equivalent weight and construction falling from the same altitude, the impact energy would have been the same, but it would have penetrated much less deeply (maybe an inch or two) before the yield strength of the material was reached... course, it might STILL have been able to impart fatal impact blunt force trauma to a human had they been impacted...

That's where I really see a "lack of respect" for the risks and dangers of launching larger, heavier, more complex rockets... I've seen guys lobbing "bigger, faster, more expensive" HPR rockets with no more care than the average 8 year old sending up an Alpha III or Big Bertha... Obviously the energies, mass, altitudes, and velocities involved are MUCH greater for the larger rockets than the smaller ones, but I've seen more than a few instances where I was thoroughly NOT impressed with the mindset or skillset of the person flying such a large rocket... and the same sort of juvenile giddiness at the resulting "spectacular destruction" when something went wrong... couple that with outright stupidity of things like needlessly overbuilding or using excessively strong non-frangible materials or design, or needlessly complicating the build (like using shear pins on a rocket flown at a field with a 2500 foot waiver, where no shear pins are required, but which cause a deployment failure that results in a large HPR rocket impacting off-site in a surrounding neighborhood and destroying an awning on a house, fortunately nobody was under it at the time!) Throw in things like "bowling ball lofting" and you've got plenty of stupidity to go around, IMHO...

That said, we cannot eliminate ALL possibility of injury or death, period, except one way-- NOT TO FLY AT ALL. Nobody's proposing that, including me. What I DO think we need to seriously look at is some of this "yahoo" type flights and behaviors and attitudes, and actually do some defining not only of activities but also of materials involved. What exactly constitutes a "substantial part" (which cannot be made of metal?) IMHO, a "nosecone" and a "fin" are "substantial parts" and therefore are disallowed to be made from metal, but yet THEY ARE BEING SOLD AND ADVERTISED... and I've read more than a couple build threads with folks using them or something like them. What about where the mechanical yield strength, weight, and other similar properties of composite materials are similar to the same specifications for those parts were they made from metal?? IOW, if you'd be "just as dead" getting hit by a spiral wound fiberglass cone as an aluminum cone, then we should be asking why EITHER are allowed?? If the probability of your limb being severed or slashed to the bone by a carbon fiber fin is similar to that of an airfoiled aluminum fin, then why are EITHER allowed?? What limits should be placed on design and material choices for certain parts, and what can be done to make them safer?? Can frangible joints or "fracture lines" be engineered into them (slits cut or pre-thinned areas specifically designed to shatter on impact and absorb the impact forces (like "crumple zones" engineered into cars) to minimize or prevent serious injury in the event of an incident, and what form/requirements should that take??

"Blowing up the rocket" isn't the answer... for one thing, it would violate the safety codes about carrying explosive devices not specifically designed as part of the motor or recovery deployment system. (the "no warheads" rule). The other thing is, in the case of these large/complex/heavy/high powered/high strength rockets for which the problem primarily exists, the risk isn't just the single large rocket falling out of the sky... in many cases, 'blowing up' the rocket into a mass of shards of hard/brittle/sharp/dangerous chunks of materials falling out of the sky would actually multiply the danger, rather than abate it... Remember a video a couple years back of some yahoo that put about 20 pounds of birdshot in a HPR nosecone for "ballast" to make some obscenely short, fat HPR rocket stable... and he had a motor cato a few hundred feet up and ended up showering the crowd and vehicles with lead pellets falling out of the sky?? I remember some rather interesting discussions about that one on some of the other forums (shortly before they were shut down as "divisive needless speculation")... I also remember some heated disagreement between some HPR folks about which was riskier-- having a solid mass of 20 pounds of epoxy and pellets all glued together coming down which MIGHT hit ONE person, or having 20 pounds of birdshot pellets coming down separately in a much larger debris cloud which would LIKELY hit MANY people, but with far less force... The same thing applies to "blowing up" wayward HPR rockets.

Personally, I think overall we need to take a closer look at exactly WHAT is being flown, WHY it's being flown, and WHERE it's being flown, and WHO is flying it (and their qualifications and attitude toward safety issues). I think some projects and rockets need a firm "no, not here" answer given, and if someone can't take it, too bad... there are venues for such projects that are better suited to the risks involved... but of course that flies in the face of "instant gratification" that most folks seem to have such dire need of, and while I've seen a lot of HPR guys that won't blink an eye at blowing several thousand bucks on a weekend of flying in rockets and motors, they whine like a two year old if they have to drive an extra hour to get to an appropriate flying field... Bet they'd REALLY scream being told their Mach II all aluminum tipped carbon fiber minimum diameter "space needle" project will have to be launched from Nevada rather than the local HPR field...

Later! OL JR :)
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Commander said Dec 02, 2015 00:16:26


Commander
Starport Sagitta
NAR No.97971
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TedMacklin said Dec 02, 2015 02:09:53
Make no mistake about it, both Tripoli and now the NAR have blurred the line between "model rocketry" and "amateur rocketry". These high power rockets are definitely NOT models...they are in fact real rockets and capable of causing real harm when things go wrong, up to and including death.

Calling these launch platforms "experimental" in no way negates the fact that they are inherently dangerous. Tripoli actually celebrates this fact every year with their LDRS event which stands for LARGE and DANGEROUS ROCKET SHIPS if I remember correctly.

I went to one of these at Argonina, KS in September of 2011. Had a family reunion of sorts at my nephew's house. It was quite a spectacular production with participants from all over the world. The redhead from Mythbusters was there as were all of the major vendors. Lots of big rockets, drag races with multiple fliers and a monster that went 31,000 feet. I've got a video of it somewhere.

Did I mention that winds were steady at 25 mph and gusting well over 40? So much for "the Rules".



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Commander said Dec 02, 2015 03:48:25
A lot of understandable distrust there Luke. If they were on my land I would be laying down the same rules.

The thing that scared the excrement out of me were these pictures which I tried to upload earlier. The pics were uploaded over ten years ago and the comments on the pages are mostly of the "how cool is that?" variety. I tend to think more along the lines of damn someone could get hurt. I remember reading a while ago about a demonstration I think G. Harry Stine would do. they would launch a rocket against a plate glass window and the window wouldn't break. How many of our newer rockets would pass that test?

Link to original webpage for pictures (pictures are copyrighted, I am using them under fair use for editorial purposes.)

Commander
Starport Sagitta
NAR No.97971
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Commander said Dec 02, 2015 04:05:02
I think you hit the nail right on the head Mack, High Power rocketry isn't really hobby rocketry anymore, it's amateur rocketry. While most of the participants aren't the old fashioned basement bombers, calling them hobby rocketeers is like calling some NASCAR drivers soap box derby participants. As far as I can tell, the only thing that would make them part of model rocketry is the replaceable nature of the engines.

I don't know at what level the cut off point should be. whether the two G limit in the safety code is a good point or whether that is even too much. What I do know is that we can't stay as fortunate as we have for these 50 years. We have passed one unfortunate milestone that truthfully may not have occurred if all the safety code were followed. (still waiting for news from the NAR...). If we allow those with Tim Allen fever to continue to dominate, well it won't be good.

All that being said, I just want to say that I am not against high power rocketry. I do think that a majority of the participants are safety conscious and try there best, I just think it is a time for a parting of ways, so to speak.
Commander
Starport Sagitta
NAR No.97971
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TedMacklin said Dec 02, 2015 04:55:52
I am also not against high power rocketry or those who are drawn to it. I fully understand the allure. The fire, smoke and roar of these is breathtaking. But I think that when large crowds are present the risk increases especially when there are inexperienced spectators present. The same thing applies to highways: more people of varying skills and traveling at varying speeds is a recipe for disaster.

The pictures you posted of that large rocket embedded into the seat of that car/truck should be handed to every person at any high power launch...just before they park the car and tell the kids to go play. Would you let your kids run around the infield at a sprint car race? I think not.

And while I'm on my rant, drag races should be between two dragsters and not between two (and usually more) rockets. One rocket in the sky at a time is plenty until successful deployment can be seen.

I think it is far safer to build your own rocket motors than it is to fly them in a crowd.
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luke-strawwalker said Dec 03, 2015 15:12:26
I hear ya, Ted...

When I got back into rocketry around 2003-4, I attended a number of high power launches around Texas... It was something novel and I found it quite interesting at the time... the typical "oh wow!" factor... and I agree, on a superficial level, it is quite impressive... the size, the sound, etc... BUT, I was soon taken aback by the lax attitude toward safety and the "hold my beer and watch this" and "no harm, no foul" mentality. Not EVERYONE was that way, to be sure, but everyone seemed to be very tolerant of it... and I've seen plenty of attitude just like it from folks on the forums and other websites and stuff that certainly reinforces that perception. I've seen a lot of "rules are for other people" sort of attitudes (similar to the 25-40 mph winds not "stopping the fun" like Macklin mentioned) and other such stupidity. I saw a guy I was talking to nearly take a roughly 2 foot long, 4 inch diameter heavy plastic nosecone to the side of the head as he was assembling a motor in a lawnchair when the altimeter set off the charge a guy at the next table was working on... Had the guy in front of me been sitting about a foot back from where he was, he'd probably have been killed right in front of me, because the charge kicked the nosecone another ten feet away, dragging a huge parachute wadded up behind it, and clattered to the ground. The recoil from the ejection charge going off was like a mortar, and sent the av bay and recovery section backward with recoil, snapping the altimeter board and protruding sled off when it impacted the guy who was prepping it in the gut. The tube then slammed into him and knocked the wind out of him. As he was being given first aid, when they pulled his shirt up, he had a perfect "circle with a slash across it" mark on his belly where it hit him, like a "Ghostbuster's" sign... Later as we were preparing to leave that same launch, a two stager failed to airstart and came in ballistic, and impacted on the other side of the parking area... All this was 'laughed off' as "a typical day on the range"... I've also seen a big 6 inch diameter nosecone, with weight in it to stabilize a short, fat HPR rocket, come in ballistic after overflying a crowd of several hundred or more and the parking lot behind it... it would have undoubtedly been a fatality had anyone been struck.

The real miracle is that it hasn't happened before now. When you throw in instances where people have ZERO common sense and do things "just because they read about them and thought it was cool" (like, say, for instance, designing a HPR to use shear pins, despite the fact the launch site being flown from has a 2500 foot waiver and the air pressure change that could cause a premature separation from tube pressurization wouldn't be a problem flying at the low altitudes of the waiver... and then subsequently either doing insufficient testing or improper preparation and then having the rocket actually fly "off site" and crash through an awning on the back porch of a house in the surrounding neighborhoods... (which calls into question the wisdom of the club in flying HPR on a site surrounded on all sides by urban sprawl right up to the fences, which means anything going "over the fence" is GOING to land on someone's house, car, patio, etc...) Then there's the abject stupidity of things like "bowling ball lofting" and mass drag races and other such stupidity which simply multiplies the dangers from the ever present risks...

That's why I'm GLAD there are NO HPR venues within 65 miles of me... and the next closest, which is IMHO the only really SUITABLE field currently in use (as the other is surrounded by homes/businesses/urban sprawl on all sides) is about a 2.5 hour drive away... NO WAY would I ever allow HPR on my property, given the things I've seen and read about, pictures like the one posted before... etc. One of the scariest I ever saw was a picture from a desert launch where a guy was riding a dirt bike or something and a HPR came in ballistic and impacted the REAR TIRE of his bike, and totally crushed and mangled the rim and tire and fender... I mean DESTROYED it... Now anybody who's ever seen a dirt bike KNOWS that the rear tire is what, a FOOT or two behind the rider's back... I have NO doubt whatsoever that would have been a fatality had the rider been hit directly. IOW, he missed being killed by a foot and SHEER LUCK! A split second either way, a foot off either way, and he'd have been dead, period. Yet this sort of thing only elicits comments like "COOL!" and "WOW!" from 95% of the HPR crowd. And when you start to mention safety procedures or changes or requirements to add things like shunts or pull pins to open circuits, to avoid incidents like the one I mentioned earlier with the tabletop charge deployment that happened right in front of me, you're INSTANTLY attacked from about three sides by "yahoos" that insist you're just a "nervous Nellie" trying to "spoil their fun".

Certainly doesn't inspire confidence...

I'm not "against" HPR, per se, I'm just against the way that, from my experience, MOST of the HPR community conducts business, their attitudes towards it, and their attitude toward safety. IMHO about probably 3/4 of the people flying HPR SHOULDN'T BE... not without a MAJOR attitude revision...

And, yeah, probably 90% of HPR is actually, in honest terms, "amateur rocketry". IOW, it should be conducted as amateur rocketry, not "model rocketry". When you have a rocket weighing from 20-several hundred pounds, relying on complex electronics for deployment, constructed out of heavy weight components like sonotube, lumber, heavy fiberglassed or carbon fiber composites, using rocket motors with sufficient power to lift things like snowmobiles to some altitude (more abject stupidity), etc., those things pose a LARGE HAZARD if everything doesn't happen EXACTLY as planned... With your typical model rocket, or even large midpower rocket, the risk is MUCH lower... not that its ZERO, but much lower... and the consequences are, in most cases, less severe... I'm not denying that a wayward MPR could potentially kill, if conditions were right, or that property couldn't be damaged, but the risks are less...

So what should the "definition" of model rocketry be?? IMHO, if you cannot get your jollies with up to TWO G motors in a single rocket, you need to find another hobby... Like big, huge rockets?? You CAN do that, without building 200 pound monstrosities requiring enough rocket power to orbit a small car... John Pursley, former "American Spacemodeling" magazine editor and experienced rocketeer, showed us a few years back some of his work using ultra-lightweight construction methods, mostly using 1/64 lite ply and depron foam... he was making a Saturn IB rocket that would use depron foam to make the cluster of tanks, which were in the 3-4 inch diameter range, for the first stage, and a lite-ply upper stage in the 1-2 foot diameter range... That would put the entire Saturn IB in the 6-8 foot tall range... If that's not big enough for you, IMHO you need to find a different hobby... What was cool was, John DOES NOT fly HPR... All his "super size" rockets are designed to fly as MODEL ROCKETS under the vehicle weight, propellant weight, and impulse restrictions... THAT is the kind of rocketry that *I* find impressive.. IMHO a trained chimp can build a 50 pound rocket out of sonotube slathered with fiberglass, and any idiot with a credit card can buy a motor big enough to shove into their anti-tank round to get it "outta sight" for "fast-n-loud" flights showering the ground with white hot metal particles (more abject stupidity) but it takes real BRAINS, real SKILL, to build a rocket that large that can fly on "model rocket" motors and be "strong enough" to survive, without being an antitank round...

Later! OL JR :)
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