Is a Pro38 I540-15A real?

[RocketRoll]

In 2022, I bought a Pro38 I540 advertised as an I540-16A White Thunder. I'm silly for just noticing this now, but the packaging I received says it's an I540-15A White Thunder. The QR code instructions point me to instructions that list 15 seconds as the maximum delay time:



But my packaging and this table are the only places I see that state a max delay time of 15 seconds (vs. 16 seconds). The vendor website I bought it from (Apogee) says 16 seconds. The Pro38 website product lists 634I540-16A (and no 634I540-15A). Thrustcurve.org does not list a 15-second delay time as an option for this motor (it lists 16, 13, etc., seconds). Long story short, I cannot find ANY reference to a maximum delay time of 15 seconds anywhere except on the packaging and in the linked instructions.

Has anyone seen a discrepancy like this? Apogee is a large reputable company so I doubt this is "fake"... right? My rocket has an optimum delay time of 16.5 seconds in sims, so I'd really prefer 16 vs. 15 seconds.

 

[SDramstad]

With that long of a delay you really should stick an altimeter in there. Much more accurate.

 

[mikec]

When CAR certified it, it was called a -16A (see http://legacy.canadianrocketry.org/Motor.php?c=3&motor=634 I540WT-16A ) but delays only have to be accurate to within 20% so 15 or 16 are within the error bars. NFPA 1125 — 8.2.7(1)(b) No time delay shall be measured to have a variation greater than 1.5 seconds or 20 percent (whichever is greater, but not to exceed 3 seconds) from the labeled value.

 

[mrwalsh85]

I mean, if it's in your hands, it's probably real.

 

[Steve Shannon]

As @SDramstad and @mikec pointed out with a delay that long you should not expect timing precision. Delays just are not precise. They’re tested at a single elevation and the result is supposed to be adjusted to sea level pressure. They’re launched from a higher elevation usually, and to a much higher altitude hopefully. It’s simply not realistic to expect the timing to be very close.

 

[RocketRoll]

Interesting - I didn't know of that tolerance for the delay timing, but it makes sense. Still, it's curious that the packaging lists a different nominal delay than the rest of the online sources and database. But, I suppose I won't worry about it too much, since the labelled value of 15 seconds is within the ~20% tolerance.

 

[mikec]

Interesting - I didn't know of that tolerance for the delay timing, but it makes sense. Still, it's curious that the packaging lists a different nominal delay than the rest of the online sources and database. But, I suppose I won't worry about it too much, since the labelled value of 15 seconds is within the ~20% tolerance.

Agreed, this seems like an odd little detail. FWIW, last time I flew an I540 was at LDRS29 in 2010 and my log says I used a 15-second delay, so it's likely not a recent change.

So I think the chances of Apogee having had anything to do with this are nil. And no one is going to go to the trouble of producing a fake reload like they might a Rolex watch and getting the labeling a little wrong...

 

[tbonerocketeer]

Absolutely real, The delays have been published differently on packages and have differed from teh published sheets. It is real, treat it with the number on the pack.