[F-FT] RMS delay question/comment

That was my impression from one of your posts. Sorry if I misunderstood.
Reply to
Phil Stein
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For the Pro series of motors that incorporate an ejection charge, that modification is outlined in the reload instructions and is approved by the sanctioning organizations.
Anthony J. Cesaroni President/CEO Cesaroni Technology/Cesaroni Aerospace
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(905) 887-2370 x222 Toronto (410) 571-8292 Annapolis
Reply to
Anthony Cesaroni
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Which is exactly my thesis. I have two Aerotech RMS cases; a 24 mm which I use for MR and a 32mm that came with the Phoenix kit which is in the build queue. Following the current rules (which I do) I match the 24mm reloads as closely as possible to the rocket (usually my Estes Silver Streak) and add mass to the nosecone to tailor the flight profile so ejection comes as closely as possible to apogee.
And I'm OK with that.
But now that age, skill and income have all crossed a magic threshold I am ready to move on to HPR. Level 1 certainly, and in a year or so Level 2. In the HPR regime, I am NOT happy with having only a few, discrete delay times available. With the exception of the fuel grain and delay time every other single parameter affecting construction, prep, launch and recovery are up to my discretion and judgement as a rocket flying hobbiest.
And, I don't care to mess around with the fuel grain. CTI only offers two reloads for the 2 grain 38mm case. I have designed a rocket around those fixed impulse levels which (I hope) will fly pretty nicely. I'm happy :-)
But, even using the DAT it isn't possible to get the 11 second delay time my sims have indicated would be optimal. I'm not happy :-(
I'm particularly unhappy that the prohibition against modifying delay grains is an artifically imposed restriction, based on guidelines first adopted forty years ago which do not (and, to be fair, couldn't have at the time) recognize the revolutionary changes brought to the hobby when reloadable motor systems became available.
So, as Gary indicated, when and if RCS chooses to submit variable pyrotechnic delays to NAR/TRA for testing, we as consumers need to insure that the testing acknowledges fixed delay times in multiples of only 2 or 3 seconds is archaic.
If I correctly understand what others have posted CTI initially proposed infinitely variable delay times and TRA would not accept that and insisted on only a few fixed settings for the DAT. That was wrong. Its time for the testing committees to rewrite the procedures to accomodate the technology now available to us.
John
Reply to
John Bonnett
So have you/they developed a protocol compatible with existing NFPA somehow?
Jerry
Reply to
Jerry Irvine
If that occurs, we will all then notice it was NOT acceptable when CTI arrived, but...
MAGIC
It is acceptable when you (RCS/AT) arrive!
I just love magic.
Reply to
Jerry Irvine
God bless.
See,everyone IS watching todays threads.
Reply to
Jerry Irvine
Jerry,
The instructions are non denominational and respect the separation of church and state. :-)
Anthony J. Cesaroni President/CEO Cesaroni Technology/Cesaroni Aerospace
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(905) 887-2370 x222 Toronto (410) 571-8292 Annapolis
Reply to
Anthony Cesaroni
NAR and /or TRA obviously did since CTI and Loki have variable delays.
As some bonehead we all know likes to say - You fail to comprehend. You are retarded. etc etc
Reply to
Phil Stein
Time to take your meds - retard
Reply to
Phil Stein
Incremental.
Reply to
Jerry Irvine
They can be varied from their original state. If you set one to the next higher setting and the take a half or a quarter or whatever fraction of a click off from there, that's about as good as you'll get from anything.
To get the accuracy that John seems to bee looking for, electronics might be the way to go.
Reply to
Phil Stein
God bless the queen!
Or is that Queen.
Reply to
Jerry Irvine
We'll call you which ever one you prefer.
Reply to
Phil Stein
When we introduced the adjustable delay tool with the Pro38 motors, there were no procedures in place with any of the motor testing committees to handle the concept. Therefore a plan had to be developed on the spot. Obviously with finite adjustment as per the Pro38 tool, which has 4 delay reduction settings for a total of 5 possible delay times, one could simply require three tests of each delay. And that is exactly what was done in the first run of TMT tests, 15 of each reload were provided for test, from the G60 to the J360, i.e. 90 reloads.
Note that we did initially want "infinite" delay adjustment on the Pro38 line - however, this was apparently too much of a paradigm shift for the TMT committee at the time, and they wanted us to provide preset stops instead. Thus the genesis of the current design of the ProDat tool for the 38's, which also appears in relabelled form by another manufacturer. Had the issue been less contentious at the time, we might have had an infintely adjustable tool for 38's instead of the current design. However, quite frankly, who needs delay settings between integer values in seconds? Reality is not so precise. One second off is only 16 feet of altitude and 32 feet per second in velocity, which is no problem for any properly constructed rocket and recovery system. Also, the molds are really, really expensive and a new tool is just not worth it at this time.
With the increased confidence in the concept that developed after certification testing and subsequent consumer use in the field, a reduced number of firings have been used more recently, typically with three at full delay, three at minimum delay, and intermediate spot checks. The fact is that (a) if you have your full delay length properly dialed in, AND (b) you have the coasting burn rate properly characterized, AND (c) your delay adjustment tool is properly designed with respect to the coasting burn rate, then you can actually pretty much test the top and bottom ends of the delay spectrum and have confidence in the intermediate settings. If the full delay meets specifications, and the full delay reduction setting does as well, every setting in between will be accurate within those bounds. Assuming the full delay time is on spec, the full delay reduction setting has the potential for the largest error. Each incremental setting in between will have proportionally less error as you get closer and closer to the full delay time, i.e. small delay reduction settings. However, it is perfectly rational to expect the certifying committee to spot check the intermediate delays.
As anyone who manufacturers motors with delays will know all too well, dialing in delay times is a bit of a pig. No matter how good your formulating skills and manufacturing methodology and quality control, typical cast composite delay systems vary all the time. Luckily, they tend to stay reasonably consistent within a window of error that presents no tangible risk to the vehicle in practical use. But for example [and I've done this before to get a handle on the variablity] when I cut a number of delay columns for a particular motor and fine-tune them to precise length tolerances with sandpaper (i.e. +- 0.002" or so across the center of the column), and use matched weight grain sets in the motors, I still see variability. There are myriad small variables not to mention chaos theory to contend with.
With the Pro54 system of "infinite" adjustability between bounds, it would literally take forever to test every delay three times... so the above system was used for those. The full delay was tested three times, the shortest delay was tested three times, and intermediate settings were spot checked. Jack Kane from NAR S&T was present for the first certification run of a Pro54 motor - the J210 - and was perfectly comfortable with the procedure and the rationale behind it.
I would tend to think that the first time a manufacturer brings an adjustable delay motor to market, they may be subject to a few more tests than perhaps strictly necessary, in order to put the system to the test. After that, with a confidence level established in the minds of the certifying commitee they might relax total number of firing requirements for later motor tests. That, however, is strictly for the certifying body to decide. It is what we had to do, and we had no major issue with the process.
Mike Dennett Cesaroni Technology Incorporated
Reply to
Mike Dennett
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Allow me to quibble, please. The sims for my 5.5x Streak show that with a ten second delay (achieveable with the DAT) motor ejection occurs before apogee, at a velocity of 36 FPS introducing the possibility of a zipper. If an 11 second delay were available, the ejection comes within a foot of apogee at a velocity of 5 FPS. Guess which one I like better :-)
What is really troublesome to me is the concept that the TMT committee has trouble over a 'paradigm shift' and as a result MY choices are restricted so they can feel "all warm and fuzzy". I have other issues with Tripoli which I won't go into here but I believe we need to move away from having NAR and TRA setting all the rules.
I think the time has come for a truely independent testing and certification authority whose testing results would be acknowledged and accepted by all the national rocketry associations in the US. NAR and TRA each have their own agendas. For myself, I say a pox on both their houses when they artifically restrict our abilities to build and fly rockets which are *fully* optimized. When I design a rocket which requires an 11 second delay when flown with a 260 N motor I should be able to adjust the delay grain, legally, in the same way I can use 1.1 grams of BP for the ejection charge, not having to choose between 1 gram or 1.5 grams because a 'national organization' can't make a 'paradigm shift' to accomodate newer, more versatile motor technologies.
Even though I shudder at the thought, perhaps an international FAI standard would be a better solution. AIUI the CAR has accepted infinitely adjustable delays ?
As for the testing process its self, I think three rounds for each motor would suffice. Test at: 1) full delay with no modification, 2) miminum delay possible following the manufacturer's modification instructions and 3) at a randomly selected value, again following the manufacturer's modifications. If all the results are within percent of the published values the motor and delay adjustment process are certified.
Thanks, Mike I appreciate the background information you provided.
John
Reply to
John Bonnett
As it suddenly downs on me why your instructions have you drill the propellant end instead of the ejection end: that's what's exposed before motor assembly, so that's the side you have access to. The other side has the pre-installed ejection charge already in place.
And since I'm suddenly curious, I keep seeing 1/32" per second quoted, but that only applies to AT delays, or at least some/most AT delays. Are the CTI delays also 1/32" per second, or is there some other burn rate.
It's been a LONG time, but IIRC the Rocketflite BP motors had delays that were either 1/8" or 1/16" per second, but it was definitely a faster burning delay than the typical AT composite.
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
Reply to
Bob Kaplow
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Which in turn causes me to wonder, if you drill a deep hole to shorten the delay to, say, 6 seconds, is there any danger the electric match will be inserted past the igniter pellet and fail to light the propellent ?
Pardon the dumb question, but it will be another two months before I actually touch an H143SS reload kit. Love the case, though :-)
John
Reply to
John Bonnett
Kind of like hte way reloads were first handled. You needed a second "RELOAD" Certification to use them. After a year or two that was dropped.
Any time new technology comes into the hobby, it is going to "stress test" some rules. Once the rules get fixed, the technology can flow.
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
Reply to
Bob Kaplow
The current TMT crew have no issue with an infinitely adjustable system, as I mentioned this was under prior rule, and was one individual's opinion on the situation. We were a little annoyed at the time, for sure, but have since gotten over it...
At this point both CAR and NAR have been involved in the testing of infinitely adjustable delay systems (Pro54) and all three agencies are okay with them. The only reason TMT wasn't involved in the testing was that by the time the 54's came out CAR had formed its own motor testing committee, so rather than ship motors stateside it was and still is far more practical to do it up here through CAR. That way, for example, certification testing can go on concurrently with our application for Competent Authority approval at the DOT, perhaps saving a month's delay in going to market. Besides, TMT has several motor manufacturers to deal with and it is a volunteer assignment, so in a sense CAR is also lightening the load for them. Jack Kane of NAR S&T was involved in the J210 certification testing since he was going to be in town anyways to discuss motor certification reciprocity and other issues with CAR personnel.
I don't think we have a big problem with certification of new technology at the moment, at least not from my perspective anyhow. IMHO the TMT staff over the last while have been very open minded and accomodating. After all, we just went through another "new" technology in that we certified cross-brand compatible reloads. They had no issues with the concept in general, although there was much discussion about procedures etc. which is to be expected with yet another "paradigm shift" being thrown at them. They got both opinion and flak from many sources, and there were of course some dissenting opinions offered as well as agreement, but in the end TMT waded through all that and decided there was no problem with the concept within the "jurisdiction" of a rocket association motor certifying committee. And the consumers of said products certainly seem to have no objection...
The problem with only testing one motor of any delay time as suggested is delay variability, see my prior post. One point tells you nothing, two points leave you guessing, three points is a minimum to infer any trends. It is very common for two of three to test really close to each other, while another sample sits close to the limits. If you test the full delay time and it is 14.1 seconds, then you test a -10 setting and the delay is 6.8 seconds, what can you infer from that? Nothing. Which one was off? Who knows? You need more data points, or what's the point of having a certification process at all? (some may chime in with agreement on that one, I am sure)
While it would be nice to only have to fire three examples total using three different delay settings, realistically that process would not be doing the consumer any favors at all. The system as it has been implemented so far [though it is not in stone] is IMHO a reasonable compromise between testing three of every possible setting, and not testing enough.
I suppose one way of separating the delay time from the certification process is to do it with an electronic timer, but integrate it with the motor in some manner or as an add-on module! Interestingly, note that there are no certification processes for avionics, so even inaccurate el-cheapo timers can make it onto the field in theory.
Hmmm..
Mike Dennett
But if my rockets zippered at that speed I'd work on fixing the zippering problem. Deployments 1-2 seconds from apogee are not uncommon.
Well, you could do so if the manufacturer of that motor provides instructions on how to do so, and has the adjustment process verified through certification testing. I can still see the certifying bodies being involved.
All agencies are cool with the concept.
See above. IMHO not enough data points for confidence. Convient and economical however? No argument.
No prob.
Reply to
Mike Dennett
I haven't seen you post any questions in the TRA list which TMT does monitor. If you are a member of TRA, I suggest subscribing to the list.
Concerning the 'paradigm shift, ' I don't know what you're talking about. TMT tests what is provided by the manufacturers. To my knowledge, no manufacturer has presented what you are looking for. Most of the manufacturers monitor this list intermittently. If I'm wrong about this hopefully they'll chime in and correct me.
Also, you are notlimited to NAR and TRA rules. You are free to go anywhere and do anything you want. Although I suggest that you keep it legal.
Reply to
Phil Stein

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