Nike Cajun 2 stage MPR

[rharshberger]

The Nike-Cajun was a replacement for and nearly identical to the Nike-Deacon, and it bears a pretty close resemblance to the Nike-Apache as well (all sustainers were less than .75" diameter difference and used similar sustainer fins afaik).

From the Left: Booster Airframe (BMS T188-34), Sustainer airframe (BMS T20-34) the wrap on the fin section is already in place and papered. The wrap is a piece of 1/16" balsa wrapped around the airframe, the paper is applied before wrapping and keeps the balsa from trying to split as its rolled around the airframe, the TBII glue used is allowed to soak the balsa for about 30 seconds which seems about right for wrapping, the angled transition section of the wrap was done with the balsa flat prior to application. Also pictured are the payload section which is also wrapped (sorry no pics of either wrap process), the BNC-20BB (BMS once again), and the coupler for the Electronics Bay and the 24mm MMT for the Booster (BMS T50-34, sustainer is 18mm MD).

2nd from Left: Inside parts of the booster and interstage, centering rings 1/8" plywood, baffle plate/chute shelf/ recovery anchor plate. The baffle plate is where I mount an eyebolt for the kevlar recovery harness, the eyebolts extra length is cut off and the bolt section is peened over the nut rivet style which locks the eyebolt in place and allows it to rotate too. The coupler (BMS C188-4) has the transition wrap of balsa applied to the upper section where it meets the interstage, the interstage section has two tee nuts installed for the 8-32 all thread that will run through the bay. The small CR is for the interstage coupler of T20 airframe tubing, which has been reinforced with 2 more shorter sections split and glued around it on the outside of it ( I had to redo this piece as the T20 piece dried non-concentric with the axis of the booster so the rocket when assembled was crooked, thank goodness I caught it before adding the interstage transition (made of posterboard hardened with CA).

3rd from Left and Center: different view of interstge coupler, in the first picture (top view) the reinforcements can be seen, the second picture is actually pre-assembly dri-fit.

Center and 3rd from Right: Interstage Transition shroud test fit, for some reason no matter how much I try there is always a small crease or wrinkle forms in these smaller cardstock/posterboard transistions.

2nd from Right: Fins prior to skinning, the fins are 1/8" baltic birch aka 3mm, and all four wieghed less than 1oz fully built.

Far Right: Fins with skins applied, the center fins have the center pieces of basswood applied and shaped for taper from root to tip, the outer two fins have the balsa skins applied. After drying the will be sanded to profile, the basswood and ply being harder than the balsa allow easy shaping since they take much more effort to remove too much material.

 

[rharshberger]

Interstage Coupler Electonics Bay:

I must be a glutten for punishment, smaller AvBays can be tough to get everything to fit into.

The bay is only 3.75" long internally and about 1.75" diameter, the Eggtimer Quantum is the airstart electronic of choice here, and will do double duty as Booster apogee deployment (I try and avoid motor eject as primary ejection source whenever possible), the opposite side of the sled has a 300mah Turnigy Nano-Tech LiPo from HobbyKing, this has proven to be a good choice of battery for this altimeter in most situations. The center two pictures of the Av-Bay are actually the same orientation but the Eggtimer Quantum and battery have been switched to opposite positions, it provided more space for the Quantum which makes it easier to pass the zip ties through the holes in the sled and secure the battery. Last four pictures are the parachute bay side of the coupler with eyebolt, charge well ( 1/2" aluminum with 3/8" bore, should hold about 1 gram of BP if needed), well nut for wire pass through, and the nuts to secure the bulkhead. The aluminum sled is way overbuilt for this application, its made from 1/8" thick by 1-1/8" wide flat stock, with the lightening holes it weight about 26 grams-ish, and the Quantum and battery add something like another 37-40 grams.

 

[rharshberger]

Assembled rocket, nearly ready for paint, shown here with the BT50 payload bay for the sustainer. I built the larger diameter payload bay for my JL3, the BT20 sized bay was just a bit too small, so now there are two payload bays for this rocket kind of like the real Cajun had different payload bays. Without motors or recovery installed (electronics installed) the rocket as pictured weighs 9.37oz (265.7 grams) and is just over 36" tall.
OR sims put the F35W to C6-7 pairing at 2761-ish feet with ignition of second stage at 4.25 seconds after F35W burn out (about 6 seconds from launch).

I will eventually need to confirm how the LDA plays into the Quantums airstart (that means reading the manual) as the Quantum iirc starts the timer from either LDA or launch (via calculating launch time from LDA velecity).

Hoping to fly this one either next month or in May probably on a E28T to A8-5 for a first flight.

 

[rharshberger]

Made a new charge well for the booster section today, I didn't like the short wide one (.5 diameter by .625" long, with .375 bore), and so made a .375" OD x .875" long with .25" bore charge well, it actually will hold a tiny bit more powder than the other charge well but I wanted a longer narrower charge well.

I also got color coats on most parts except the fins, booster is OD green, interstage flat white, sustainer and small payload bay are Testors Steel color, and BT50 payload bay for sustainer is Testors Model Master Fluorescent Orange. Fins will be the usual three red one yellow.

 

[OverTheTop]

Looking great!

Not sure what you have planned for the avionics on this. I did a 1:6 scale kit bash of a Nike Apache Cosmodrome Rocketry kit for this. Link here to the build thread.
https://forum.ausrocketry.com/viewtopic.php?f=6&t=3997
Tight for avionics, especially the skinny payload bay. You might find something useful.

 

[rharshberger]

Booster deployment and airstart will be handled by a Eggtimer Quantum. Due to space limitations the stage separation will be via motor separation.

 

[tim cubbedge]

Maybe I am missing something but what happens if the booster separates due to drag separation? Or will the sustainer motor light before drag separation?

 

[Charles_McG]

The Quantum times from launch, which it back calculates.

The drogue channel can be set to ‘nose over’ in airstart mode. The main channel will be your ignition.

 

[rharshberger]

Maybe I am missing something but what happens if the booster separates due to drag separation? Or will the sustainer motor light before drag separation?

There will not be drag separation, the sustainer is only 2-3 ozs with motor, recovery, and JL3 payload. Motor will light before separation, since its a Estes BP motor and the interstage will be lined not much damage should occur.

 

[rharshberger]

The Quantum times from launch, which it back calculates.

The drogue channel can be set to ‘nose over’ in airstart mode. The main channel will be your ignition.

Thats what I had thought and had sort of planned on. Looks like the maiden flight will be in two weeks.

Ignition of sustainer for first flight will be Launch +5 seconds (based on OR sim of stack being at or above 100 fps at ignition), ignition timing will be re-assesed after altimeter data is reviewed for second flight.

 

[Charles_McG]

I really like how you did the interstage. I’m thinking of doing a Paiute-Tomahawk, and have been thinking of a cardstock and foam interstage instead of getting another Sandman piece.


Sent from my iPhone using Rocketry Forum

 

[rharshberger]

Colors are done, chose a mish-mash of colors for visiblity and scale like purposes. Sustainer OD green (HS Camo brand, can was about 10-15 years old), all other colors are Testors. Sustainer airframe is Testors Steel (small square bottles), the payload bay is Testors Model Master Fluorescent Orange. Fins are Testors Model Master FS series Insignia Red and Insignia Yellow. Interstage is Testors Model Master Flat White. Once the rail buttons are re-installed and the booster recovery system install this rocket is ready to fly.

 

[BDB]

Colors are done, chose a mish-mash of colors for visiblity and scale like purposes. Sustainer OD green (HS Camo brand, can was about 10-15 years old), all other colors are Testors. Sustainer airframe is Testors Steel (small square bottles), the payload bay is Testors Model Master Fluorescent Orange. Fins are Testors Model Master FS series Insignia Red and Insignia Yellow. Interstage is Testors Model Master Flat White. Once the rail buttons are re-installed and the booster recovery system install this rocket is ready to fly.

View attachment 341226

Looks great!

 

[rharshberger]

For a recent request for information, this interstage is not used here but I might be how I would do it for a larger more powerful rocket. Materials would be mostly FG or Birch ply whichever was most appropriate.


View attachment 5 to 3 interstage idea.ork

 

[FMarvinS]

Looks great Rich! Please post some launch photos when available.

Fred, L2
member ICBM,SC
KG4YGP

 

[rharshberger]

Looks like I get to type the flight report twice tonight.

Flew the Nike Cajun today, staging a F24W to a A8-5 using a Eggtimer Quantum to airstart the BP motor. The flight was mostly a success, mostly because all the parts were recovered when the sustainer shockcord burned through and snapped at upper stage ejection. At the same time the shockcord broke the nose cone tape sheared and the payload bay nosecone, JL3 and foam carrier for JL3 were ejected for the 1142' fall to the ground. We fly on a sod farm so all parts turned out to be very easy to locate, the nosecone with the foam carrier landed 30-ish feet from the sustainer at which point I am guessing the JL3 popped out of the foam carrier and landed within a foot or so of the fluorescent orange nosecone, no damage to any of the parts beyond the shock cord. The payload bay now empty, landed under streamer about a 100 yards away and the booster landed normally under an 18" chute about a 100 yards beyond that.

The flight staged at 795', but due to 7-10mph winds (or higher at that altitude) the rocket weather cocked a bit more than expected and the sustainer only got about another 250' of altitude to 1142', of course I got a bit of a razzing about using a A8-5, when a C6-5 would have been more interesting. Thank goodness I used the smaller motor. Attached below is the graph from the JL3. The Apogee for the Booster was less than a 100' higher than the staging altitude, so in the future I believe with a F24W booster motor I will modify the staging timer to be 4 seconds instead of 5. Definitely looking forward to getting a flight up with a F35W and one of the new Quest Q-jets in a 18mm D.

 

[BDB]

Looks like a great flight with a fortuitous recovery. What lock-out settings did you use on the quantum?

 

[Charles_McG]

I built mine to do I to G. Having now seen G-F, I'm thinking G-E or G-F is plenty. A8 was probably wise.

So now I have a G65 WLB and an I104 IMax that I don't quite know what I'll do with. The Ute-Tomahawk might get pushed higher up the build list.

 

[rharshberger]

Looks like a great flight with a fortuitous recovery. What lock-out settings did you use on the quantum?

I dont remember but I will check later, iirc the only lock was something like a 100' or 150' altitude check. LDA was set fairly low as well iirc. I l may have it all wrong though.

 

[Charles_McG]

I think getting all your parts back counts as a success.

I don’t think you can set the minimum altitude less than 300’, if you are using it. You allowed a nice long coast, so you were well above the minimum.

I’ve been trying (relatively) small booster motors and short coasts (to see better) and have run into that 300’ minimum minimum altitude.

 

[rharshberger]

I think getting all your parts back counts as a success.

I don’t think you can set the minimum altitude less than 300’, if you are using it. You allowed a nice long coast, so you were well above the minimum.

I’ve been trying (relatively) small booster motors and short coasts (to see better) and have run into that 300’ minimum minimum altitude.

You are probably right, I can pull up the airstart mode later and see what the settings are. Just for general information the igniter for the A8-5 was a chinese Ematch as I have heard CJ suggest in the past, worked like a charm.

 

[BDB]

You are probably right, I can pull up the airstart mode later and see what the settings are. Just for general information the igniter for the A8-5 was a chinese Ematch as I have heard CJ suggest in the past, worked like a charm.

That’s what I’m using in my C11 sustainer motor too. E-matches are quickly becoming my favorite way to light a BP motor.

 

[rharshberger]

Evidently the Quantum does not save setting when the mode is switched to the opposite mode. However the settings I used were

LDA: 150
Launch Samples: Default 20
Descent Samples: Default 4


Drogue Timer: Nose Over
Drogue Min Alt: Off
Drogue Alt Chk: @Timer
Drogue Min Vel: Off
Drogue Vel Chk: @Timer
Drogue Pulse Width: 2 Sec
Drogue Use BW: NO

Main Timer: 5.0
Main Min Alt: OFF
Main Alt Chk: @Timer
Main Min Vel: OFF
Main Vel Chk: @Timer
Main Use BW: No

 

[BDB]

Evidently the Quantum does not save setting when the mode is switched to the opposite mode. However the settings I used were

LDA: 150
Launch Samples: Default 20
Descent Samples: Default 4


Drogue Timer: Nose Over
Drogue Min Alt: Off
Drogue Alt Chk: @Timer
Drogue Min Vel: Off
Drogue Vel Chk: @Timer
Drogue Pulse Width: 2 Sec
Drogue Use BW: NO

Main Timer: 5.0
Main Min Alt: OFF
Main Alt Chk: @Timer
Main Min Vel: OFF
Main Vel Chk: @Timer
Main Use BW: No

It looks like you didn’t use velocity or altitude safety lockouts. Am I reading that right? I wonder if the launch detect altitude can function as a defacto safety lockout?

 

[Charles_McG]

It looks like you didn’t use velocity or altitude safety lockouts. Am I reading that right? I wonder if the launch detect altitude can function as a defacto safety lockout?

If it was so unstable it didn’t get to LDA, maybe. But I’d set it higher in that case.

Consider, though, that this is LPR black powder to black powder. If it were direct staged, there would be no safety lockout, and nobody would have a problem with it. (It wouldn’t have a coast either.)

Mine is bigger. And in 4 flights, I’ve been asked once about lockouts, and that was by the pad assistant, not the RSO.

Went back and re-read. Not bp in the booster. But still, A8 BT20 sustainer.

 

[rharshberger]

Lockouts were disabled for the first flight only to determine how the actual flight compared to the simulation data. I was fairly comfortable with the simulation data, but now I need to pull all the information together to determine actual staging velocity. Visual tracking was easy as it was a very clear day with light wind. Weathercocking was a slight issue

 

[Charles_McG]

I see Quest 18mm D16s are certified now

 

[rharshberger]

I see Quest 18mm D16s are certified now

Yep, and this rocket might be a prime candidate for them...

 

[BDB]

If it was so unstable it didn’t get to LDA, maybe. But I’d set it higher in that case.

Consider, though, that this is LPR black powder to black powder. If it were direct staged, there would be no safety lockout, and nobody would have a problem with it. (It wouldn’t have a coast either.)

This is a good point that I hadn’t really considered before. When my daughter fliers her Estes Mammoth with a booster F15–>F15), it has more total impulse than my electronic staged test rocket (F50–>C11). I’m probably over-thinking all of this.

 

[rharshberger]

Well, heres a update on flight #2, the velocity lock was engaged ( because I feel that there need to be altitude lockouts lower than 300' the alt check was disabled). Staging did occur but rocket was horizontal away from flightline when it occurred, even with the timer set to one second less than previous flight on the same booster motor ( an F24W). The Quantum also did not fire the deployment charge at apogee and booster came in ballistic, possibly rebuildable, but I probably wont. Aluminum sled angles and all threads bent, one terminal block, the beeper and one other part were shorn off the board ( verticle 3 pronged thing between main drogue terminals). I will be contacting Cerving, for parts to see if I can fix it to recover data from flight. The JLCR's op rod was also bent but after straightening it worked fine, but I do need to contact John Beans for a replacement.
Will post photo this evening when I get home.