10" lightweight Atlas Missile

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burkefj

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Watching Aerostadt rebuild his 10" Atlas got me to finally think about doing one with a lightweight foam superstructure. I've had pretty good luck so far using foam for lightweight large rockets. I want to do a missile version however, not the mercury-atlas because I prefer missiles I guess. My target is to do it the same size as Bob's but have it weigh the same as only the nose weight he used for his model, 5#.

I'm hoping that 1/16" makrolon fins will be tough enough at this weight, they do weigh 2.5oz each so heavier than I would like.

So, I'll attach an early openrocket file(without the side fairings) but you'll get the idea.

10" diameter, 82 inches tall, 5# or so AUW is the target. I'll try my normal method of using a 29mm core tube with a 4" parachute bay at the top, the warhead section will fit into the 4" parachute bay via a coupler and will be the part that ejects. Altimeter on the side near the transition with wiring that routes up the 29mm tube into the parachute bay. I've got some bt-70 for the warhead.

Frank

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Ordered the stuffer tube and upper 4" centering rings and a pml 4" coupler, and some kevlar line, the rest I have or I'll do myself.

Did a first pass estimate of the rtf weight.

Part weight
Stringers 10.8
CR 4.2
Skin 5.6
Stuffer 5.1
ParachuteTube 4.8
Large plyCR 10.9
small ply cr 0.9
Fins 3.8
balast 0.0
motor 9.0
parachute 5.0
eye bolts 2.0
retainer 0.5
altimeter 2.0
glue 2.5
paint 0.0
kevlar+nomex 1.0
Nose 6.0

Total 74.1
 
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Did some shopping, got some chrome and silver trim monokote, some small eye bolts and a BT-70 balsa coupler for the warhead nose, I'll turn it to shape. Also did some looking for nozzle material. Found some kids drinking cups that looked like they might do the part, but on the way out I saw some krylon grey sandable primer on sale, the caps were sort of bell shaped and were already grey, they also were a nice flexible plastic and have a close to 29mm flange on the inside, I figure I'll slide the center one over the 29mm motor tube and hold it in place with adhesive and the outer two I'll use screws and washers to hold them in place. To keep weight light it will not be a cluster, just a single motor.
I used my silver sharpie to make some lines around the nozzle for effect just to see how it would look.

Frank

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Spent a few minutes during lunch with my belt sander and converted the balsa bt-70 coupler into my nose cone for the warhead...


Frank

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Here I show the 12" long parachute bay, 2.5" of that will be taken up by the centering rings attaching it to the 29mm stuffer tube, leaving me 10" of parachute space. I made a 1/2" wide reinforcing ring on the top of the bay to help prevent any zipper risk. I then made two ply plates for the nose cone/warhead. One was to center the warhead tube onto the bottom piece. I then made a depron transition, covered the tube in white trim monokote and attached them together. The balsa cone has a carbon rod that goes allmost the full length and ties the nose into the base plate, so if it hits hard it will prevent the tube from crushing. Once I get the couplers in from wildman, I'll add those to the base plate to complete the warhead/nose section.

Frank

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Fabulous project!

I remember that fondly. I still have the footage on my old .39 Productions VHS. The ring of G38 FJ motors around the center K1050's gave a super cool effect. And they were lit with bare Daveyfire e-matches which is interesting to know. but they used the old size that fit in them - they don't make that size anymore IIRC.
 
Did a few of the bits and pieces while I'm waiting for the stuffer tube. The ply 3/32" thrust plate and top plate which will have the rail guides mounted. Rail button ply mounting pieces(1/4" ply), Wiring harness to go from the altimeter bay about mid body, up through the stuffer tube into the parachute bay, the stuffer tube cap(deployment charge wire will pass through this cap and it will fit into the stuffer tube to cap it off and seal the tube and wiring from the deployment charge, and the altimeter capsule, this is velcro'd into the altimeter compartment in the rocket and sealed off by a magnetic door. It basically holds it from moving around and protects the altimeter in case of a hard landing. I used this in all of my foam rockets, some have the capsule built into the rocket, some have it removable. By making it removable I can mount the altimeter higher in the rocket and make the door smaller since I don't have to be able to fit my ham hands into the door to connect wiring, I can pull it out, work on it and then just stuff it back in.

Using one of the ply plates as a template I cut out my foam centering rings, took about 10 minutes to do 12.

Frank

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Here are the initial templates for the centering rings and stringers, I haven't cut the center hole out since I don't have the stuffer tube yet to know the actual hole size. The stringers will slot/tab into the centering rings spaced 6" apart, they will not go all the way to the stuffer tube. Since my sheets are 39" long, i needed something divisible by 6" so I went with a section 36" long and a second one 12" long to give me the 48" length or the lower body tube, this will be able to be covered by a single 49" long 2mm skin section. One slot on the centering ring is double wide, because I'll use two stringers here next to each other which will give me a wide area to glue the skin joint to. I've found that it is really hard to have a perfectly straight stringer only 6mm wide to glue the skins to at the joint. I won't cut the transition centering ring/stringers till after I assemble the parachute bay/stuffer tube and measure the required size.

Frank

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Some more work after dinner, finished all the stringers and centering ring notches, and assembled the lower stack, I used a glass to show the final height of the parachute bay to give an idea of the finished height. Airframe weight now, without skin is 13.4 oz

I've added a supplemental centering ring between the bottom two, which the fin will slot into, this gives more gluing surface to support the fin attachment without requiring making a fin box, this has worked well in the past. So the fin tab will glue to the top, bottom, middle centering rings and the fin root to the stuffer tube. This is needed to reinforce the fin joint since you can't rely on strength of glue joint/fillts to the skin since it is only 2mm foam...(this is one of the differences in building this way, similar to rail guide attachment...anything you need a solid attachment that will take any load needs to be tied to the structure/stuffer tube)


Frank

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This is fun to watch. The low weights are amazing! The Master of Depron can really bang out these parts fast. I assume that the 2 mm depron is considerably more flexible than the 6 mm depron.
 
Yes, the 2mm is pretty flexible, but still not easy to wrap around anything smaller than 6" without heat and being smart in the design...Most of this you can cut out with just one or two passes of an exacto so pretty quick.

Frank
 
Did some work on the short side conduit/fairing, turned out ok. 3/4 oz covered. I'm not 100% happy with the way the covering went over the compound curves, but If you squint really hard it won't look too bad....

I was trying to see how to get a better fit of the parts to the fuse, the problem is that the skin is soft, so I don't want to sand against it, so I took a spare 7.5" loc coupler, slit it and slid it over the airframe, it conforms pretty well and gives me something hard to build/sand/test fit against.

Frank

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here is an updated parts weight list, I track the GOT, growth over time and update my simulation

Part weight
Stringers 11.0
CR 6.0
Skin 5.6
Stuffer 5.1
ParachuteTube 5.0
Large plyCR 7.5
small ply cr 1.0
Fins 3.8
balast 0.0
motor 9.0
parachute 4.5
eye bolts 1.6
retainer+nozzles 2.1
altimeter 2.5
glue 2.5
paint 0.0
wiring 1.5
kevlar+nomex 3.8
Nose 6.0

Total 78.5
 
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I can see a few differences in the Missile Versions some models seem to have equal long conduits, some are unequal, some are unequal but the short side is really short on some and on others a bit longer, E and F have the big equipment hump, F model has the side fairing skirts even with the bottom of the airframe, D and E extend down a bit..F models seem to have a skirt with two separate angles while the D is a straight taper..i wish I had some drawings or descriptions that better showed all the variations as it seems there were a bunch of different conduit shapes.



Frank
 
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Devised a good way to make the skirt, used a flat base plate, tabbed into two end pieces, and a center support, the flat piece gave more surface area for the skin to glue on near the sides and helped hold it to shape...A couple of pictures, stuck the motor nozzles in place to see how they looked.

Nozzles are a bit small for scale, but they aren't too bad. I needed something very light and robust for landing and I think they'll do the part.

I can do a lot with markers for details that will look good from a distance without having to glue things on and add weight...little things poking out of the fuse like the vernier motors will tend to get pushed through the thin skin or break off if it lands on them, same for all the piping...it's hard to have a solid attachment for something really light that won't snap or push through when pushed on...and I really don't want to add any un-needed weight on the rear half.

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DId you see these pics Frank? https://www.siloworld.net/GD-A%20%20San%20Diego%20Aerospace/ATLAS%20F/577th%20SMS/577th__sms.htm

At the bottom of the page is links to all the sites that had the Atlas F (according to Wikipedia anyways) the 550th, 551st, 556th, 577th, 578th, and 579th Missle Squadrons, the 567.th at Fairchild AFB, Spokane Wa had the Atlas E model.

The page for the 579th has some interesting shots of the missle from directly behind showing the bottom area around the engine bells.
The page for the OSTF-2 has a good closeup of the base as well in a vertical stance.

Dig around the Siloworld site long enough and there are lots of great photos, its just a pain to figure out its layout.
 
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Rich those are nice sites, good closeups of the warhead, they are all the F model with that darn equipment hump, I have seen pictures of the atlas missile on the way to fairchild...Still seeing lots of variations inthe different side tunnels...Here are some pictures I found that seem to show D models with the MK IV, one with long pointed symmetric tunnels, two with unequal tunnels, but the short side is shorter than a mercury atlas type. At first I thought there was a secondary skirt above the first one but then realized that those are doors that close as the missile lifts off..I saw that in a video, it wasn't obvious before....

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Rich those are nice sites, good closeups of the warhead, they are all the F model with that darn equipment hump, I have seen pictures of an atlas missile on the way to fairchild...Still hoping to find some pics of a D model with the MK IV warhead if that existed, and some of the different side tunnels...Here are some pictures I found that seem to show D models with the MK IV, one with long pointed symmetric tunnels, two with unequal tunnels, I thought there was a secondary skirt above the first one but then realized that those are doors that close as the missile lifts off..I saw that in a video, it wasn't obvious before....

Dig deep enough on the Home page of that site and you will get all kinds of D models, space launchers and ICBMS both. Go to the bottom and click the HOME button, then scroll all the way to the bottom of that page and click the Atlas Missle Bases button, then scroll to the bottom of that page and you will get all the D,E,F bases and photos.

https://www.siloworld.net/ICBM/ATLAS/ATLAS.HTM bottom of page to get to other missle models

https://www.siloworld.net/MISSILE%20%20LAUNCHES/missile__launches.htm Cape Canaveral and Vandenburg Atlas missles and launches.This one is really neat in that it has lots of different payloads, not just warheads, Pioneer, Midas, Mercury and other payloads.
 
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You are right, there are a lot of great pictures, I focused on the D model launches, in those there are a bunch of different tunnel lengths/combinations/humps..Interesting.
 
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Rich those are nice sites, good closeups of the warhead, they are all the F model with that darn equipment hump, I have seen pictures of the atlas missile on the way to fairchild...Still seeing lots of variations inthe different side tunnels...Here are some pictures I found that seem to show D models with the MK IV, one with long pointed symmetric tunnels, two with unequal tunnels, but the short side is shorter than a mercury atlas type. At first I thought there was a secondary skirt above the first one but then realized that those are doors that close as the missile lifts off..I saw that in a video, it wasn't obvious before....

The middle photo, with the red tail section is sort of a bastardized display model-- It may be an Atlas A with a sustainer engine thrown in, or it's an Atlas B, with a warhead of a later model that didn't fly on either type. Only A and and some B models had the pointed tunnels of matching length.
 
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