TLP Nike Ajax Upgrade / Multi-Stage

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Feb 9, 2009
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So I'm moving on to my first more advanced project since becoming a BAR. Having built literally dozens of Estes and Centuri kits in the old days, and then quite a few "upscale" kits since returning, it didn't take me long to get to the point of wanting to do something "more."

This project is essentially an upgrade build of the TLP kit. I have to agree with the majority of the on-line reviews about the quality of the componentry included in the kit, generally speaking they are not top-grade parts, and for the asking price ($55 or so), I'd expect more, especially after getting kits from outfits like Hawk's, Q-Modeling, and similar.

About the only good thing in the kit are the plans, some of the detail parts and the balsa stock isn't as bad as it's made out to be!

So far, I've replaced the body tubes, engine mount (3x 4" vs. 3x 3"), and will replace the parachutes with more solidly built nylon examples.

For the multi-stage aspect of the project, I plan to follow the general guidelines as set forward in This Review.

I'll take pictures as I get going, but for now have a couple of questions (based on an image from that build):


Using the interstage as the "nose cone" for the first stage makes a lot of sense. I can even see how the whole thing can go together - at least using the components included in the kit.

The kit uses a BT-50 "keel" to hold the two stages together. This is held in place by two CR-5080s in the booster and two CR-5060 in the sustainer. The reducer is just a paper wrap that connects the BT50 "keel" with the BT60 sustainer tube.

If you use a BT80 coupler, the CRs and a balsa plug in the BT50, you can essentially make the base for the interstage "nose" cone.

From there a single CR5060 is used to anchor the wide point of the reducer, and a BT60 coupler goes on top to slide into the sustainer stage.

At least that's how I see this thing going together.

Question becomes, how to best anchor the BT60 coupler to the top of the interstage so that it's firm and can handle the load of the friction mounted (and likely friction mounted at that) sustainer stage?

I can see pooling epoxy at the bottom, but want to see if there are any other ideas here.

Some (actually most) of the replacement parts should be here this week, so I look forward to taking folks through a build thread here, not only to share my experiences, but to get commentary along the way. While I'm an experienced builder of standard and even mid-power kits, I know I still have lots to learn when it comes to electronics, higher power, and more advanced concepts like the staging here!

BTW - this will be "proof of concept" for a 1/5.3 scale high power version. In working through the scaling, I figured out that the LOC 75mm (3") and 54mm (2.26") tubes worked out PERFECTLY to scale for the proportions of the real thing. That model will finish out at a touch under 74" tall, and will fly on 2 38mm mounts.... But we'll save that for another thread.


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Hi you might want to have a look at my build thread on this rocket on the previous page of this category. Ted
I did review that thread, you provided some interesting thoughts about the interstage. One difference for my project is that I will be using standard timer electronics to fire the sustainer - as suggested by the article that I linked to.

Some of the upgrade parts arrived today, I'll take pictures as I go.
Instead of creating another new thread here, I figured I'd just ask here since it's related to this project.

Can anyone recommend a source for getting custom CRs and similar parts made? I've contacted Semroc and Flis to see if they will, but on the chance that they don't, I'm looking for further recommendations.

I need to make some odd-sized CRs for the interstage for this model:

1x BT80 Coupler ID Bulkhead with a pilot hole for a screw eye
2x BT50 OD – BT80 Coupler ID CRs
1x BT50 OD – BT80 OD CR
1x BT50 OD – BT60 OD CR
2x BT50 OD – BT60 Coupler ID CRs
1x BT60 Coupler ID Bulkhead

Since this isn't just BTXX OD - BTXX ID that's why I need the special parts, and since these will all be load bearing (or most will) I need them to pretty good tolerance, and thus don't want to sand down normal CRs.

And barring anyone that does custom parts, how about a precise measurement for the following:

BT60 Coupler ID
BT80 Coupler ID

The couplers that I have are Semroc, so I don't know if that makes a difference.

I do have a local laser source, so I can fall back to that, but since they don't know rockets, would need to provide just the measurements.


So after getting a better look at the Alway plans for the Nike Ajax, it became clear that this project was going to be a complete scratch build. I had already replaced many of the structural components from the TLP kit, now the details of the fins, etc. needed to be replaced as well. Also with the LONG tapered nose cone, it was clear that the kit provided nose cone wouldn't work.

So I started scaling everything out. I used the dimension of the booster tube diameter as the basis from which all other scale data were derived.

Booster diameter (actual) = 16.5"
BT80 BT used for booster = 2.600"
Scale Factor = 2.600"/16.5" = .158

So based on that scale factor, I derived the following:

Booster Diameter 16.500 2.600
Booster BT Length 130.063 20.550
Booster Transition Length 3.500 0.553
Booster Transition Top Diameter 17.500 2.765
Interstage Gap 5.437 0.859
Interstage Transition Length 18.813 2.972
Interstage Transition Bottom Diameter 9.000 1.422
Interstage Transition Top Diameter 12.000 1.896
Sustainer BT Length 156.844 24.781
Sustainer Diameter 12.000 1.896
Sustainer Transition Length 61.781 9.761
Sustainer Transition Top Diameter 7.000 1.106
Sustainer Nose Cone Length 14.000 2.212
Booster Fin Root Chord Length 37.120 5.865
Booster Fin Tip Chord Length 10.502 1.659
Booster Fin Semi-Span 26.480 4.184
Booster Fin Forward Sweep Length 13.310 2.103
Sustainer Main Fin Root Chord Length 74.500 11.771
Sustainer Main Fin Semi-Span 20.000 3.160
Sustainer Sm. Forward Fin Root Chord Length 10.375 1.639
Sustainer Sm. Forward Fin Semi-Span 3.000 0.474
Sustainer Lg. Forward Fin Root Chord Length 20.000 3.160
Sustainer Lg. Forward Fin Semi-Span 8.751 1.383
Sustainer Vane Length 154.969 24.485
Sustainer Vane Width 3.625 0.573
Sustainer Vane Thickness 0.000
Sustainer Vane Bevel Width 0.000
Nose Vane Length 54.031 8.537

The first number is the measurement of the prototype, while the second number is the scaled value based on the .158 scale factor.

This is where the first scaling question comes in - since the sustainer should have a diameter of 1.896" - which corresponds most closely to a ST18 tube. The kit's sustainer is based on a BT60 sustainer, so it's at touch more than a quarter inch too small in diameter.

I had originally figured up all my centering rings (and there are a LOT of them) based on a BT60 scaled sustainer, but I'm thinking about re-working those to get a closer to scale model.

BTW - this thing scales out to just short of 62" in length.

Since I'm a scale modeler first, I tend to go for maximum detail and scale effect, but I want to take practicality into account, as now I'm potentially going to be looking at a bunch of non-standard CRs mixing Estes sized tubes with Centuri sized tubes.

Since Carl had already said he'd make the CRs, I guess I can change those up based on the ST18 tube (vs. BT60).

Once I get that settled, I should be able to move forward rapidly with this project.

A different issue that I'm working through is the staging timer, and how to build that into the nose. Right now, I'm planning on building a transition around a ST11 tube to handle the majority of the "nose cone" (9.7" of it), that will reduce to 1.1" at the top, and be capped by a 2" ogive NC. I'd like to be able to use the inside of the ST11 tube as the electronics bay for the staging timer. Any recommendations for what will fit? I'm just getting up to speed on timers and similar.

I'm planning on using the same headphone jack disconnect for the igniter wires that have to run to the base of the sustainer. Having the staging timer in the NC also completely balances the model from a stablity standpoint.

Just trying to share some of the calculations that I've been working through.

Thanks for reading!

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I can see from your work that my TLP Nike-Ajax is sport scale at best. I'm not happy about the shape of the supplied nosecone either but I can live with it.
Are you going to profile the fins? I didn't notice any data on fin thickness or profile. The booster fins are a diamond shape decreasing out to the tip chord. I didn't have info on the fins thickness so I arbitrarily made them 1/2" decreasing to 3/16". I wimped out on the sustainer and NC fins and made them flat with sharp bevels.and a long bevel on the rear of the sustainer fins to simulate flaps. The NC fins are are diamond profile decreasing to points but the sustainer fins look to be a more complex shape. I'm watching your build with interest. Ted
I'll probably do a degree of profiling, but not totally to scale, if you did scale thicknesses, many of the features would be difficult to achieve. So I'll figure out a way to represent most of the features, but they probably won't be to scale.

No when, I do the high power version, I'll definitely construct profiled fins, as at that scale, I can build out the structures more easily.

We'll just see once I get the basic shapes lasered - I'm going to have a couple of sets made, so I'll have some spares...

I'm interested in how your headphone jacks work for reliable separation. I wasn't confident that I could rig a reliable wire disconnect so I used a long wire from the"NC" of my booster to the base. I got a fair bit of blast damage to the interstage from the sustainer ignition. Are you planning to separate the sustainer before ignition? If yes, how?
For my next 2-stage project I'm planning to use an ignition system in the sustainer that will be activated by separation of the stages. If I could disconnect the NC with the battery in it from the wiring it would improve my design. Ted
I took the idea for the head phone jack from the original review that I linked to above. I'll use the timer, probably the same PerfectFlite that he did as it'll fit in my ST11 electronics bay.

As for the specifics of the headphone jack, I'm going to use a Koss jack, as they're VERY small, and the disconnect force required is small. I have the luxury of having a whole herd of EE types that work in my group here (we do all the retail experience device prototyping for AT&T), they helped with the recommendation for small size and light pull.

I got word from Carl at Semroc that my rings would be done in the next few days, so as soon as those arrive, I'll be off and running.


BTW - as for separation, I'm still working on that. I'm hopeful to figure out drag separation, so that the booster just falls away once the motors burn out, but in order to have the connection between the stages be strong enough, there will have to be a pretty firm fit between the stages.

Worse comes to worst, I'll use the ignition of the second stage to do the separation, and will coat the top of the interstage coupler and inside blast plate with foil, much like the builder did in the example that I linked to.

I could use external lugs to hold the booster and sustainer together, but there would be nothing scale about that. I also tried to figure out how to use the interstage support "fins" to act as lugs into the reducer at the rear of the sustainer. The problems there would be that the slots in the sustainer boat tail would have to be VERY precise in order to not bind, but still be rigid enough to support any lateral forces from "bending" the upper stage (sustainer) loose from the lower stage (booster).

So, the short version is, I'm still working on it...

The new tubes showed up on Friday (ST sized, closer to scale), and the CRs shipped today. I'm hopeful they'll be here on Wednesday, can't wait to get rolling.

Sent the fin plans off to be lasered as well!
So I'm finally getting some spare time to get started on this project, and the custom parts that I ordered are now showing....

Here's an overall image of the non-fin components:


The BT80 for the booster is already cut to length (20 9/16) is at the rear.

The ST18 for the sustainer is next to the back. It's one 18" tube joined with a 6 3/4" section for a 24.75" sustainer main airframe.

Next forward is a ST13. This will act as the keel that holds the whole thing together. I selected this as the bottom diameter of the sustainer boat tail is a scale match to the ST13 OD. There will be a short section that mounts inside the "interstage" nose cone for the booster (about 3.5") - with about 7/8" showing in what should be the gap between the boat tail and the booster cap. Not to scale, but there has to be some structure to this thing.

The final tube is a ST11. This will be used as the electronics bay, and was selected as it has the right diameter (again to scale) for the top of the conical transition that makes up the majority of the Nike Ajax "nose." There is a 9.75" taper before you get to the actual cone at the tip. This will be mounted via CRs to a shortened ST18 coupler.

Speaking of the nose cone, you can see the semroc ST11 cone in the foreground, as well as in this photo:


That cone matches as closely as I could find (without going totally custom). It is almost dead on the length (2.1") for scale, and has the right ogive shape.

And then here are the mass of CRs that will be required:


If I arranged them properly, those go from bottom to top, and will be used for centering tubes within couplers, tops of transitions, and even some details (there is a raised ring at the top of the sustainer boat tail for example).

The rings were purchased from Semroc, and were custom made to spec.

So the cutting has started, the fins have been drawn in CAD and should be lasered this week. I'll keep the construction photos coming as I start to build out some of the sub assemblies.

One of the only debates that I'm still having is whether or not I'm going to use the original TLP clustered 24mm mount (via a nice Sunward mount kit that was much nicer than what came in the original TLP kit), or just switch up to a single 29mm mount. The 29 is more scale (single rocket and what not), but the cluster is more practical for sport flying....


So I had a busy August - made a little progress, and had intended to post this sooner - I have the main coupling sections pieced together - but am trying to find a reliable way to make the transition templates that I require for this project. Rocksim does a nice job of allowing for templates, but then has terrible support for printing those out.

Here are two images of the interstage. This will end up being the "nose cone" for the booster:



The coupler is a 2" section of a BT80 HTC, with a ST13 body tube mounted by two CRs - the booster transition will be added to the top of the HTC - it will be 1/2" long. There will be a HTC13 at the front (the end of the ST13 that protrudes from the BT80 coupler) that will connect the booster and sustainer.

The rear CR is flush with the back of the HTC, the hole will be covered by a smaller bulkhead. The forward CR is set inside the HTC in order to allow for a good glue filet on both sides of the CR. The structural CRs that are shown are all 1/8" lite ply. The CRs that will be used as the mounts for the transitions are 4-ply paper board.

This will be the nose cone & electronics bay for the sustainer:



The tube is a ST11, and the coupler is a 1" HTC18, it will act as the shoulder for the entire "nose cone" assembly. Same process was used with the CRs, the rear CR is flush mounted, while the forward CR (which as of these pictures had not yet been glued) is inset to allow for better filets. There is a similar bulkhead that will be used to cover the base end of the assembly, but it is still being measured and fitted as it will have to be removed to allow access to the electronics bay and wiring (staging timer, which will ride inside the ST11).

Sorry if this still looks basic, or is too detailed in showing my process - it's the first time I've done a build thread. I hope it'll get more interesting.

Wow, it really has been a while since I updated this - fortunately I'm making build progress again!

I spent most of the fall, and right up until Christmas break getting all the custom fins and reducers designed, drawn in CAD, and finally burned by a laser...

That stuff is all done, and I actually have parts, and further progress to show.

More once I get the pictures loaded up!
As promised here are some pictures - first we'll start with the components that I have been working on over the last few months - since I only get to be at the laser cutter a couple of times a month, it was slow work, but after a lot of refining, it all came together.

First some of the fins:

Here are the booster fins - these are cut from 3/16" balsa stock. You'll note some fins for the Scud-B cut from the same sheet - that's my next project. These were setup as first pass cuts, obviously any future sheets will be more compact, and won't have the SCUD fins.


Here are the sustainer fins - the main fins are the most prominent:


Here is a close-up of the forward fins for the sustainer - these had to be designed with the angle of the forward reducer in mind. The forward third (give or take) is a conical reducer - and not a straight tube ending in a more traditional nose cone (one of the first things that caused me to dismiss the TLP kit). Note the grid on my work mat vs. the shape of the fins:


Next up is are the supports for the interstage - these were the toughest to design as the had to fit to the custom reducers, and custom ring that was to become the booster cap - note these were v1 of the supports, we just made v2 today, which I'll show in my next post (as I actually have them assembled).


Now we move on to the custom reducers - these were all laser cut, and designed to fit the tubes on hand. As an added measure we added (where appropriate) laser marked lines that show where to attach the fins. The medium sized are the sustainer boat tail, the long/large piece is the sustainer cone, and the thin piece is for the booster cap.


I don't know if the next two pictures will show the laser markings where the fins attach, but that was the purpose of the next two photos:



Back with a little build progress later...
So, as promised, here's some actual progress, vs. just raw parts!

Let's start with the completion of the booster cap:



The forward section of the booster actually flares out on the actual Nike Ajax. While the booster airframe is 16" in diameter, the booster cap flares out to 17.5" in diameter. So I setup a custom cut reducer to represent this. We also have a couple of custom centering rings to act as the frame and mounts for the reducer.

Once the reducer was framed, and glued, the inside surfaces of the reducer were coated with epoxy to add strength to the walls.


Once the cap sub-assembly was completed, it was glued on to the booster "nose" cone assembly that was shown in previous posts. While the ST13 that protrudes through the center is actually not scale, that tube has to be there for a couple of reasons - to add stability to the lengthy model (basically act as a keel holding the whole thing together), and then - if it weren't going to be staged, there would have to be a duct for the ejection gases to eject the recover system. So regardless of the flight profile of this rocket, that's the one exception to scale that has to be made.

The final detail is the top plate of the booster, this was done by adding another ply CR to the top of the cap assebly - matching the outer (scale 17.5") diameter.

The next step was to roll the other reducers.



Here you see the in-progress rolling, and the finished product. Using the age old technique of curling the reducers over a piece of doweling, the reducers were pre-curled, and formed up beautifully. Even those with the laser-cut alignment marks didn't score. So the concept worked perfectly.


Here's the longer nose cone reducer as well.

I'll break this into smaller chunks, so I don't get timed out by the forum.

Hope you enjoy!

Moving along - let's look at finishing the interstage/booster cap...


Here are the components for the interstage supports - as I noted in the components post, these are actually the final refinement. The interstage supports - the main struts that connect the booster cap and sustainer cup - had to be very carefully designed so that they matched to the angle of the sustainer cup, and the height of cup above the booster cap. Once those were complete, and fit perfectly, I then designed the cross-braces. The outer brace matches to the outer profile of the support, and features a laser-scored line where the part should bend to match to the support. This allows for consistent fitting from one part to the next.

The inner braces align flush at the bottom and form a small notch at the top - this notch acts as the vertical alignment for the sustainer cup on the interstage supports.




So here are the completed sub-assemblies. Everything lined up just as planned. Once these were dry, it was a simple matter of using the laser-cut alignment marks and the notch on the top of the inner brace to even align these around the sustainer cup.


Fortunately all that refinement paid off, and everything lined up perfectly. This assembly was set aside to dry.

Now we come to one of the first questions that I'm still dealing with on this project - so I'll turn to those of you that have a little more experience in electronically staged rockets.


There is a ST13 coupler that will act as one of the two supports that will hold the sustainer in place during the boost phase of the flight. This goes back to the need for the ST13 running up through the booster cap - where on the real thing, there's open space.

I envision the sustainer acting like a boosted dart and separating from the booster at the moment of booster burn out. With the large draggy booster cap, and all the interstage supports, I can see the separation working - particularly if I have very little attaching the booster and sustainer.

However, therein lies the risk - how much do I need to brace the sustainer during the boost phase such that it stays in alignment with the booster, and doesn't try to shear off (I know careful fin alignment, and all that).

There are two support mechanisms that I have designed in. First the sustainer cup - the reducer that was attached to the interstage supports will "cup" the boat tail of the sustainer - just like the real thing (albeit without the mechanical attachments).

This will work to a certain extent, but will still be prone to allowing lateral movement by the sustainer during boost.

Thus the reason for including a tube coupler inside the cup. So the question becomes - where to position the coupler - do I go 50/50, or allow a little more to protrude forward into the aft of the sustainer, allowing for more grab during boost - but more friction to prevent separation at burnout. Or do I push it back with only 25% protruding into the aft of the sustainer. That will provide a little lateral support during boost, and less friction at separation.

Again, I'm turning to those of you that have had some experience in this realm.

Obviously I can ignite the sustainer right at burnout using the timer - booster burn times are predictable - but then that increases the damage to the interstage at ignition.

I am planning on foiling the inside of the sustainer cup, the tube coupler, etc. and figure that a little flame damage during each flight is unavoidable (and with careful construction will be of minimal concern) However, ignition, while everything is still attached comes with a pressure component that I can see causing more damage than if I can facilitate separation at burnout.

Alas there's still time to get it all refined before everything gets glued together.

Here's what the resulting booster cap/interstage sub assebly will look like:


The base pieces of the supports will be epoxied to the booster cap with plenty of strong fileting around all of the key joints.

Finally a couple of other sub assemblies


Here is the nose cone assembly. This is the reducer set over the nose cone core (as previously built in this thread). The ST11 at the center will act as the electronics bay for the staging timer. More on this once I get further into the electronics.


Here is the booster engine mount - I had originally set my sites on the 3x 24mm x 95mm mounts - similar to the TLP kit that got this whole process started. Three E9s perform nicely in Rocksim for this thing, but at this point I'm debating whether to move to a single 29mm mount allowing for a greater variety of booster engines.


And finally, we have the aft sustainer components. At center is the ST13 core that will first act as the mate to the booster stage, and second as the core to the sustainer boat tail (that is at the right of the photo). The right tube, is the after portion of the sustainer main tube. Since you can only buy ST18s in 18" lengths, there has to be a second section of ST18 to make up the full 24.875" length of the main sustainer tube. So this is the aft 6.875".

Assembling in this fashion has the added benefit of allowing for easier installation and covering of the ignition wiring assembly prior to running the wire to the front of the sustainer tube to the attachment point for the electronics.

Obviously a lot more on that once I get to that point - which is really about the next step in the process.

I think that about covers it for this round - I look forward to your comments.

Have some electronics questions that I posted in the Electronics Section

If you're so inclined, and have some experience with staging timers, have a look.


So I'm back at work on this project (actually, there's been a little progress in the interim) after finishing up my HPR project. I have all the sub-assemblies largely read to roll (still have a bit more fin shaping to finish up), and then it's off to the races.

The only barrier that I'm still facing, is my wiring for the staging timer/e-bay.

Right now I'm planning on using one of Adrian's Ravens for the controller - to achieve three purposes:

1) Staging firing - on burn-out of the booster (actually slightly after)
2) Apogee separation of the sustainer (backup deploy should the sustainer engine not fire)
3) Main Deploy - the more I looked at this thing, the clearer it became that it was going to get on up there, and, frankly, I didn't want to lose it to a long drift after main deploy at apogee.

So now, I've designed a more traditional mid-ship e-bay, instead of using the nose. This allows me a bit more room - 1.8" dia. by 3.5" long should be more than enough space for the Raven - and actually a few other products.

But that leads to a few questions:

1) When I run the leads back down to the motor area from the headphone jack, do I just put stripped leads down there, and twist them to the igniter wires? How do y'all hook up your electronically staged igniters? I know some run long leads from the igniter itself right to the ports on the timer/ignition circuit, but I don't see a way to disconnect that seeing as the timer is going to be in a e-bay.

2) Anyone have a design for a smaller ebay using more standard parts? Right now I'm thinking of a short (1.75") section of airframe tube with two HTC's doubled inside (3.5" long total). I can make a fixed bulkhead on the lower end, and I can make a bulkhead for the top, but I'm not aware of a good way to make that top bulkhead removable - without significantly weighting up the rocket. So if anyone can help with that, it would be most helpful.

3) With the Raven, is there any threat to not detecting apogee? Seems like that one is toward the top of the reliability meter... Any other good choice that can handle: 1) Staging and then 2) Dual Deploy.

I'm sure there will be some follow-on questions, but let's get started with those. Hope to have some pictures to show of the latest progress shortly!