For the Pro series of motors that incorporate an ejection charge, that
modification is outlined in the reload instructions and is approved by the
Anthony J. Cesaroni
Cesaroni Technology/Cesaroni Aerospace
(905) 887-2370 x222 Toronto
(410) 571-8292 Annapolis
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
to the nosecone to tailor the flight profile so ejection comes as closely as
And I'm OK with that.
But now that age, skill and income have all crossed a magic threshold I am
to move on to HPR. Level 1 certainly, and in a year or so Level 2. In
regime, I am NOT happy with having only a few, discrete delay times
With the exception of the fuel grain and delay time every other single
affecting construction, prep, launch and recovery are up to my discretion
judgement as a rocket flying hobbiest.
And, I don't care to mess around with the fuel grain. CTI only offers two
for the 2 grain 38mm case. I have designed a rocket around those fixed
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
have indicated would be optimal. I'm not happy :-(
I'm particularly unhappy that the prohibition against modifying delay grains
artifically imposed restriction, based on guidelines first adopted forty
which do not (and, to be fair, couldn't have at the time) recognize the
changes brought to the hobby when reloadable motor systems became available.
So, as Gary indicated, when and if RCS chooses to submit variable
delays to NAR/TRA for testing, we as consumers need to insure that the
acknowledges fixed delay times in multiples of only 2 or 3 seconds is
If I correctly understand what others have posted CTI initially proposed
variable delay times and TRA would not accept that and insisted on only a
fixed settings for the DAT. That was wrong. Its time for the testing
to rewrite the procedures to accomodate the technology now available to us.
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
To get the accuracy that John seems to bee looking for, electronics
might be the way to go.
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
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
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.
Cesaroni Technology Incorporated
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
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
so they can feel "all warm and fuzzy". I have other issues with Tripoli
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
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
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
As for the testing process its self, I think three rounds for each motor
suffice. Test at: 1) full delay with no modification, 2) miminum delay
following the manufacturer's modification instructions and 3) at a randomly
selected value, again following the manufacturer's modifications. If all
results are within percent of the published values the
and delay adjustment process are certified.
Thanks, Mike I appreciate the background information you provided.
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!
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
touch an H143SS reload kit. Love the case, though :-)
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!
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.
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
All agencies are cool with the concept.
See above. IMHO not enough data points for confidence. Convient and
economical however? No argument.
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
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