Hi gang, Robert Kieffer here. John has summarized things nicely, but let me provide a bit of additional context.
I raised this issue with John while implementing an auto-suggest feature for motor delays in an app I'm building. Briefly, the idea is that after a user selects a motor, they are shown a list of the "official" delays available for that motor. E.g. If the user selects the "Estes C6", they would see delay options of 0, 3, 5, and 7 seconds. This is straight-forward for BP motors from Estes, obviously, but gets a little tricky for adjustable delays like those from Aerotech and Cesaroni where the options depend on the tool and method used to drill the motor. Hence the question(s) here. (For those interested, here's
the Github issue where John and I have been discussing this.)
tfish wrote:
Both Aerotech and Cesaroni don't seem too concerned about this. I'm not saying it's not good advice but I can't find any verbiage about this on their websites, nor does there appear to be anything built into their tools to prevent this. E.g. You can use the Aerotech tool to remove up to 8 seconds from their "S" (6-sec) and "M" (10 sec) delay grains.
Similarly, Cesaroni's PRO-38 DAT tool allows for removing up to 9 seconds of delay from their 24mm-38mm motors, many of which ship with delays <= 12 seconds.
(Aside: Is this issue already taken into account in how delay grains are designed? If a delay grain breaks down under a certain length, doesn't that happen to all grains once they've burned down to that point?)
Do you know of an official source for this requirement?
mtnmanak wrote:
The goal here is to reflect the delays that are
achievable with the official delay grains and delay drilling tools available. While it may not make sense to remove 8 seconds from an Aerotech "S" (6 sec) delay grain, there's nothing to prevent you from doing that. (Whether it's
wise to do so isn't an issue the thrustcurve DB should be concerned with, IMHO. John may feel differently, however.)
I will reluctantly point out that with core-burning motors you can actually have negative delay values. (The delay grain starts burning at motor ignition but delay times measured from motor burn out. BTW, someone should correct me if my understanding of how this works is incorrect.)
E.g. if you have a motor with a 4 second burn and a 6 second delay time, the delay grain actually burns for 10 seconds starting from motor ignition. If you shorten that grain by 8 seconds, you aren't actually drilling all the way through it. You're just setting it to burn through 2 seconds before motor burn out, resulting in an effective delay of -2 seconds.
... but I say "reluctantly" because the I don't know of any use cases where this worth considering. Hence, my suggestion is that delay times should always be >= 0 in the TC db.
dhbarr wrote:
I believe this is correct. I think John my have fumble-fingered that.
