AIM-54 Phoenix scale nosecone

augendoc

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All of the kits of the AIM-54 Phoenix that I have seen have a tangent-ogive nosecone of variable ratio. If you look at actual photos and also Peter Alway’s drawing in “Various US Rockets of the Cold War” the nosecone is definitely not a standard ogive or tangent ogive nosecone. Peter’s drawing is more like a 2:1 secant ogive from the tip to the chine, and straight from the chine to the coupling with the body tube. The pics of the real missile show the chine to be faired or rounded over to about a 1” radius. Short of turning this nosecone on a lathe by hand, does anyone know what the actual nosecone parameters would be, and if that shape is available commercially?
 

augendoc

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ERRATA: the Peter Alway booklet containing the info on the AIM-54 Phoenix is titled “Selected US Navy Missiles of the Cold War.”
 

MarsFire

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This kit has the correct nosecone and fin profile with "fin brackets" and motor nozzle. A bit on the pricy side but very nice looking. I have always liked the older (waterslide decals) Estes kit. It looks great in the air and has a sweet whistle as it boosts but is let down a bit by the obviously too long nosecone.


Andrew
 

augendoc

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Thanks for the link. That's a nice looking kit. I especially like the fin fairings. The nosecone, alas, is not quit scale and is still too long, though better than most other kits on the market. Per Peter Alway's drawing the length of the curvy part of the nosecone is very close to 2x the diameter. There is some parallax in the eBay photo but I am getting a quick and dirty measurement of 1:2.34 for the curvy part.
 

ShadowSpire48

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I got close when I printed a new nose cone for my Madcow 2.2" Phoenix
 

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MarsFire

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I have the kit so I took a quick measure. Now I admit its pretty hard to tell EXACTLY where the "curvy" part ends and I wasn't using calipers but 5.5 inches looks pretty darn close. Remember this kit is sized for LOC 2.56 tubing with an OD of 2.630 inches. That comes out to 1:2.091. Pretty close.


Andrew
 

CTimm

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Maybe this will help.
 

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augendoc

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Nice pic, thanks. From the pic the ratio of that nose cone is just about exactly 2x diameter from the projected tip to the soft shoulder. I wonder if the part forward of the shoulder is really a secant-ogive or maybe a haack cone. From a scale model perspective It doesn't much matter as the two are probably very similar. There's got be an engineer out there that worked on this thing and probably knows. Or maybe I could ask the Iranians...
 

PeterAlway

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I don't have my source material immediately available, but I think I got the bulk of the information from some Navy drawings that Jim Ball sent me ten or twenty years ago. Over at Ye Olde Rocketry Forum, there is some discussion of Phoenix source material, and some scans of what is probably the same drawings that Jim Ball sent me many years ago. I don't know the exact profile of that curve--it is some form of secant ogive, where there is a corner at the base of the curved profile, but I don't know if that curved section is a circular arc, a parabola, a Sears-Haak profile, or some other mathematical optimization. I wouldn't put money on those official drawings having the exact profile, because that is not the exact purpose of those drawings. I pretty much eyeballed the curvature in my drawing, though I might have used some sort of measurement from a photo or drawing for the diameter of the cone at the mid-length point to try to get some accuracy. But to be honest, it's been at least four years, and probably more, since I did the basic artwork on that drawing.

There might be a tangent ogive for a larger body tube that you could saw off to approximate the shape. That depends on getting lucky about a nosecone with the right diameter and length, but there's a shot.
 
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