Interesting high lights of the NAR BoD Meeting and ...

Hey Phil,

Well I can assert that Kosdon is crazy at times ... at a Balls event, he was burning up excess AP right in the prep area ... this cloud of reagents was choking serveral people set up next and NEAR him. The guys is a VERY talented rocket scientist, and VERY eccentric! God Bless him! Andd yes, the "smackdown" was laid on him by the "gaspers" and Aero_Pac personel.

Now as for the other "big name" that I dare not mention less I get a lawyer calling me, he has EARNED his expulsion from TRA and RRS ... although I see he is active at the Mojave test range from time to time, but those people let anyone in who is will to pay :)

Lunarlos

Phil Ste> >

Thank you Brian, I was trying to figure out when I was almost killed...

Erik gates

-Kevin

Probably the last time you crossed your wife... 8-}

Yes, fortunately Myth Busters hasn't had any near-misses.

What happened to Bruce on Master Blasters is darned scary, and I'm thankful it wasn't worse!

-Kevin

kevin: well that more or less looks reasonable.

shockie B)

Yes it was. And it re-enforces what I've heard about ejection charge mishaps being the #1 cause of injury in HPR.

When I was preparing for my NAR L3 I questioned the NAR requirement to physically disconnect the ejection charge from the electronics until after the rocket is on the pad and ready to fly. I now understand it and agree with it. I don't know the full details of what happened on Master Blasters, but it seems to me that a proper safety disconnect (with the charges shunted when disconnected) would have prevented the initial problem.

Good on him. I have said it before and will say it again: "Hybrids look like a pain in the rear".

I can see it. I say let him back in just so we can kick him back out again.

Yep. I, and plenty of other TRA members, don't want malcontents continually blabbering in my inbox. They can come over here and piss and moan with Bob.

Korey Kline.

I got a recent copy of SNOAR News. In it, they describe how NAR contacted any of their members that were named in a SNOAR LDRS1 article for safety code violations. Some were expelled.

I'm no fan of Bruce Kelly. Apparently, there are more fans in TRA than non fans. That's the way it is. I'm not going to go whine & stomp my feet about it. I have better things to do.

I everything I hear about Bob is true, I don't see why he wouldn't be readmitted IF he asked to be.

Based on how much experience with them? Hybrids are no more a pain than assembling an Aerotech reloadable, maybe less depending on the brand (Hypertek, for example are the easiest).

Hi Dave,

You're right about the model floating down. I think Bob was pointing out that someone slammed the launch switch while that one fellow was still close to the model. I think that is not a good habit to get into even though the prospect of damage caused by this model is low. I would not want the person handling the launch panel to do something like this with a larger model.

Kurt Savegnago

We have a club member who will be making attempt number three at launching a Hypertech M on Saturday. Attempts #1 and #2 resulted in major damage to rocket all due to the motor. Our club had launched the Hypertech M four other times with no problems.

Attempt #1:

Motor was filled per normal. Grain shattered when fired and destroyed booster. An O-ring was not installed at the factory and nobody checked since there is no way for it to go missing. The other O-rings were checked by multiple persons. The resulting small leak froze the grain.

Attempt #2:

Try #1: We thought fill stem was seated, but it leaked at fill. No launch attempt.

Try #2: Tie straps broke during fill. Enough nitrous was in the tank to push rocket up the rail up 10 feet and back down. No damage to rocket.

Try #3: Motor leaked at fill. Previous trip up the rail dislodged the Kline valve O-ring. Motor has to be disassembled to fix.

Try #4: No leaks at fill. Rocket was launched. Flame started and melted tie straps. Flame went out and nitrous pressure pushed rocket up

25 feet or so. The rocket crashed to the ground and was damaged. We believe that all the work on the motor moved the igniter wire and we didn't get the actual fuel started.

Brian Elfert

I had heard about #1. IIRC Hypertek was notified and responded well.

#2 sounds like fairly typical learning curve on hybrids. Hitting the Kline valve correctly and knowing how it feels when properly seated takes a little experience. I'm really surprised to hear that two tie straps failed at once; those suckers are pretty strong.

I could do a quick search of launch reports and find similar stories using APCP. O-rings damaged, nozzles clogged, chuffing igniters, mysterious CATOs, etc.. I think the failure rate is similar, but hybrid failures get more attention because people tend to watch when they're going off.

Brian Elfert wrote:

What's wrong with just having the battery disconnected from the electronics until everything is set up and ready to go?

Chris

Brian,

just out of curiosity, was the igniter wire taped to the inside of the grain or the fillstem on this attempt please? CTI's instructions use the method of taping the wire to the grain, but I can see problems with the igniter coming loose during prep. Someone, though I can't recall who, is using the same method for M's as for the smaller stuff (J/K) and taping the wire to the fillstem, albeit with a longer folded over piece at the end to touch the inside of the grain. Apparently they haven't had a single problem since starting to use this method. I'll go digging to see if I can turn up the reference.

G.

Nothing. Things were being set up and being made ready to go when it happpened. I don't have the specifics of what happened. A shunt is about all you can do to prevent that from happening. It can greatly reduce the possibilty but not totally 100% eliminate it.

How many cumulative hours do I have to sit and wait on hybrid flyers to get rockets off the pads before I can make the comment "those things look like a pain in the rear"? Because they most certainly look like a pain in the rear to me.

Never seen anyone spend that kind of time at the pad for AP motors, unless they are WAY complex clusters.

The assembly is not the "pain in the rear" to which I refer.

There's always the possibility of "startup transients". During the fraction of a second between connecting the battery and the electronic components all seeing steady, full-on power, there is the possibility that digital outputs will be in an "undefined" state for a moment. In other words, the output MOSFETs may see a "fire" signal for a moment, even though they will be set to "off" as soon as the electronics finish coming up to full power.

NO electronic circuit is capable of switching from zero volts to some positive voltage instantaneously. Due to the fact that all circuits have some resistance, and there is always some capacitance between conductors (not to mention the effects of power "filtering" capacitors), there is always a "ramp-up" of power over some time interval. It is not always possible to guarantee (especially in digital circuits) that the outputs of circuits will be predictable and stable during that ramp-up time.

Disconnecting the charges entirely, and/or shunting them, is cheap insurance against this sort of momentary "glitch" during power-up.

In theory, there's no difference between theory and practice.

- Rick "In practice, there is." Dickinson

It's pretty damned easy to add a time constant to the fet gate control and guarantee it'll be less than the switching voltage by the time the processor is in control.

Has this effect ever actually been seen? I'd be staggered if the amount of energy transferred into an ematch in this case was even measurable without seriously good test gear nevermind anywhere near the guaranteed no-fire spec for commercial igniters.

Chris