tavarish palkovnik Posted Saturday at 03:22 PM Posted Saturday at 03:22 PM (edited) Could somebody help to solve one dilemma about Sidewinders Seems like there are three different propellant grain forms through history of Sidewinder motors -> -first one is internally burning star (most probably 8-point star) and this grain was in AIM-9B -second one is internally burning 6-point star with cylindrical exit and nozzle was submerged. This grain form was in motors of AIM-9C and 9D (CTPB based composite) also in AIM-9L but with double based propellant. And most probably in few more Sidewinders, I guess AIM-9M is in this group -this is third grain form Internally burning cylinder with slotted aft end (most likely 6 slots). This same grain form is in AIM-9X but in that motor nozzle is externally positioned and with jet vanes included. Question is…what Sidewinder before 9X model could have motor with such grain configuration? Nozzle is still submerged as in Mk36 series and I doubt this motor remained in 36 nomenclature. It is some AIM-9 between L and X but I don’t know which one it could be Edited 20 hours ago by tavarish palkovnik
nighthawk2174 Posted 19 hours ago Posted 19 hours ago On 9/20/2025 at 10:59 AM, tavarish palkovnik said: After Russian motors, now again a little bit about American ones. I’ve already worked something about AMRAAM motors and maybe it’s time to complete it and to make it in more decent way From top to bottom WPU-6/B, WPU-16/B and just for scale size comparison RDTT-542U. AMRAAM motors are actually very similar in concept (which I don’t like at all, by the way), propellant weights are known (in previous works I missed it and gave too much for both motors). Information about exact properties of propellants are of course not known but both are from same group of HTBP reduced smoke type. What I did is that I used now exactly same propellant properties for both motors, exact same nozzle geometry and erosion rate of it and just extracted outputs following grain geometry which is slightly different in these two motors. What is kind of strange is that first motor is classified as boost-sustain and second as all boost. While first one indeed has dual thrust curve, although with not so significant pressure (thrust) drop, second one is also with output which is actually not what would be normally called all boost motor. Why they classified it as all boost I don’t know, but it wouldn’t be first case. In what I’m pretty sure, is that geometry of grain as it is must give higher starting values then when motor is finishing its work. I like much more pressure data outputs than forces but people usually are interested in forces only. Although internet write all kind of numbers for these motors and some ridiculous values of specific impulse (probably because it is HTPB and not only that, it is American and recently new HTPB) these outputs of mine I find as quite fair and realistic. It is 12400kgs and 11100kgs of total impulses or average 240s sea level specific impulse which looks fair and square. Specific impulse wise HTPB is probably in the range of 242-248. There are patents from the late 90's early 2000's which change up the blend to get it higher but these would not be relevant for the 120B/C. 1498409585215997771-06238499 US6238499B1 - Solid rocket propellant - Google Patents
tavarish palkovnik Posted 19 hours ago Posted 19 hours ago 9 minutes ago, nighthawk2174 said: Specific impulse… Don’t forget these values in most cases are given for ratio 69:1 bar or 1000:14,5 in psi. Chamber pressure vs ambient pressure, with full expansion of gases, and without losses in divergent zone of nozzle Same as Russian motors and propellants, only in ratio 40:1 which is Russian standard
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