More so than failure of the ejection to fire at all? Either could end up causing a recovery failure - so can other factors not involving the charge itself, such as mechanical issues with the airframe and parachute.
Lawn darts and core samples happen. (Often enough that there are terms for them, at least, like "cato" or "shred"... "oh, there's a word for when that happens!") It is the intent (and, hopefully, the effect) of the safety codes to ensure that such events are not actually "dangerous".
A bonus delay could cause ejection at or just above the ground, setting the ground cover on fire. "Ground Cover" could be a roof, it could be grass, it could be an umbrella, it could be someone's Jeri Curl, etc.
"Void" is not "illegal". Show me the law that makes it _illegal_ for TRA to require ATF permits or anything else over and above the minimum requirements of NFPA codes.
If you believe that TRA requirements are unnecessary, or excessive, or wrong-headed, fine. Just say so. You're welcome to your opinion. But don't say it's "illegal" when there is no law to support that claim.
I'd say that Estes motors are a lot more likely to start grass fires with a "ground level ejection" situation: their charges are more sparky (coarser BP?) and "fireworks-like", and generally located closer to the airframe separation point. (The difference in "ejection plume" was very noticeable at a night launch...)
Perhaps. Personally I'm much more worried about rockets that come off the pad at an angle for whatever reason and go "cruise missile". Of course, that's usually not a motor failure, but I do think it's the most likely thing to cause a serious injury.
In any case, lawndarts caused by motor ejection failures are quite rare in my experience. When it comes to large rockets, I've seen far more ejection failures from electronics than from "bonus delays".
I do see a lot of Estes modrocs eject after impact, but that's usually due to some kid using the wrong motor.
Jerry, If we were to do business, and I asked to see your driver's license before I'd accept your check, would that be considered "void"?
Seems if I buy a bag of chips and write a check, they'll ask for photo id (DL in most cases, unless you carry your passport every day)
Of course, some nutcase may claim "why do I have to prove I can drive before I can buy chips!"
In reality, it just a way to prove who/what you say you are, to conduct the business (a check, in this case)
Skippy, we can get you a "Certified RMR Nutcase" photo ID if you need one! (and a T-shirt too!) Hate to see you go without chips! You got to be doing something the 12 hours a day you post to RMR!
Without wanting to get involved in all the continuing arguments that go on here, in the 2001 AT catalogue PDF I have, all motors from the 54/2560 up (i.e. all 75 and 98 mm motors) are plugged. Are there any M motors which provide motor ejection? Would anyone really fly an L3 project and rely on motor ejection?
-- Niall Oswald ========= UKRA 1345 L0 EARS 1151 MARS
"Gravity assisted pieces of the rocket raining from the sky should be avoided. It is also financially undesirable."
Take a look at those standards. Both require the testing of ALL available delays for motor certification. When Tom took over TMT, he just ignored that rule and pencil whipped out all the extra certifications, test free.
There were cases where NAR failed to certify one or more motors of a particular type because the delays were wacked. Or where they forced the manufacturer to change the delay designations to match the test results. Look at the AT consumer reloads for the motors with asterisks on the label. The F39 comes to mind. AT sells them as -6, -9, and -12. S&T certified them as -3, -6, and -9 respectively.
Whatever M motor John tested, it was supposed to be a "L" which is 14 seconds. It tested WAY LONG. John said the only way he'd certify it was if it were relabeled as "XXL". Then all of a sudden, after Tom pencil whipped the certs the XXL delay was now cetified as an L. And the never tested S (who knows how long that delay was) was also certified.
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
At the time we're talking about, all AT motors, including M had motor ejection. If it's there, it has to be tested. Of course if it doesn't, it doesn't. And I'm sure that's a large part of the reason that they have dropped motor ejection on big honken motors: the cost of testing all the delay combinations was impractical.
The M motor I mentioned is not the only motor that had other delays certified without testing. It's just the one clear example I remember where John tested ONE motor, found the delay to be off, certified it as something else, and then after the fact had his certs changed to cover motors he didn't test. It happened for MANY motors throuought the HPR spectrum.
Here's the question for Ray: Let's assume for the moment that Jerry Irvine gets all his paperwork in place, and comes out with a BruceKicker J666 motor. He offers it for sale in delays of -5, -10, -15, and -20. TMT tests only ONE J666-20 and finds that its really a -33. Would you trust the rest of the delays to be what they are labeled without ever having any of them tested? Would you even certify the whole set of J motors based on ONE SINGLE FIRING? Would you put the J666-10 into your camera rocket knowing that if the delay is off by the same amount your rocket will prang and your camera will be trashed? Or would you insist that the J666-10 and the other delays all be tested before you use them in your rocket?
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
Ah, thanks for clarifying that. I'm not sure what the deal is over here, since UKRA don't certify motors (which is hardly surprising given the cost of the whole business. UKRA has something like 230 members, so motor testing would be out of the question).
Surely without testing several examples of each delay, all the user can go on is what the manufacturer says the delay is. If you have a motor which comes with 5 different delays, then maybe 25 firings are required, which means an absolute fortunes worth of motors and testing time. Would there be a way to test the delay alone, which would make things a lot cheaper?
-- Niall Oswald ========= UKRA 1345 L0 EARS 1151 MARS
"Gravity assisted pieces of the rocket raining from the sky should be avoided. It is also financially undesirable."
Unfortunately, the delay design in typical composite motors ignites the delay grain along with the propellant... since the burning rate of the delay grain is affected by the pressure in the motor, it follows that motors with different thrust curves can require different delay grain lengths to give the same effective delay (measured from burnout to ejection) - thus, it's not generally possible to do a representative delay test without an actual motor run.
That's a great question, Niall. I was wondering the same thing. On idea I had was to use a forward closure with multiple delay wells. If you could somehow prove that 3 (or 4 or 5) wells arranged in a circle around the position normally occupied by the single well would all behave more or less the same, then you could test all 3 (or 4 or 5) delays at once.
The whole key is being able to use the special closure and claim equivalence.
Also, I'd like to think that, if the curves (data) are close enough for the first three motor burns, then further burns are not needed.
So, there, I've cut your 25 burns down to 3 :)
BTW: Does anyone know how CTI tests the infinitely variable delays of the Pro54's? Now that's a lot of testing :)
I wondered as much (re the motor pressure issue), whichever way it looks like a long and expensive process to get accurate representative data. I suppose it depends how much you're willing to trust the manufacturer, if the delay was factory guaranteed then it wouldnt be such an issue.
Just looking down the I motor TMT list, some of them differ quite a bit from the manufacturers' rating - for example the I435T is an I517 according to TMT! (Peak thrust over 700N - I hope Richard Parkin flies his Cirrus Dart on the one he's got stashed when I'm at the same launch!)
-- Niall Oswald ========= UKRA 1345 L0 EARS 1151 MARS
"Gravity assisted pieces of the rocket raining from the sky should be avoided. It is also financially undesirable."
"Gravity assisted pieces of the rocket raining from the sky should be avoided. It is also financially undesirable."
Hmm, I didnt think of that one - sounds an interesting idea anyhow. Could pose some major issues with getting it to work I should imagine though!
However it would be nice to know what sort of variance to expect - you might test that theoretical J666-20 and get, say 20.5 seconds first time, but then fire another two and get 18.1 and 24.3. If you only fired one you wouldnt be able to say with any authority that the delay was 20 seconds, but if you fire several then (assuming they are regular production motors) then an idea of the likely variation can be gained, and any really bad things (like massively varying times for example) could be brought to the user's attention.
I wondered that too! I think an idea of the linearity of the scale could be gained from tests at a few settings though, but again you'd have to fire so many motors(which should flown be in rockets!!) that it would be extremely expensive.
-- Niall Oswald ========= UKRA 1345 L0 EARS 1151 MARS
That's nothing compared to the amount of motors consumed in the presently-required testing for DOT shipping classification and approval, which includes things like tossing them on a campfire by the box-load, in order to observe that, yes, they do in fact catch fire and burn up just fine, no problem (instead of maybe trying to actually explode or something).
The motors which are used for delay testing are at least static-fired on a test stand, and burned in the intended manner... the same test runs can be used to record thrust curves.
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