Thales Starstreak build

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DrewW

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Oh yeah, almost forgot....first dart is 100% complete. Three interchangeable nosecones all weighted differently so I can test stability of the free-spinning canard segment at 1.1 cal, then 0.78 cal, then if all appears well down to 0.39 cal.

For those who haven't read the whole thread, I'm inducing spin in the forward section of the missile whereas the aft should nominally fly without rotation. This should effective reduce the impact to CP from the canards and simultaneously add gyroscopic stability to the rocket. Both of these things independently should allow a rocket to be acceptably stable below the 1.0 caliber rule-of-thumb.

IMG_0070.JPG
 

BrendanH69

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Oh yeah, almost forgot....first dart is 100% complete. Three interchangeable nosecones all weighted differently so I can test stability of the free-spinning canard segment at 1.1 cal, then 0.78 cal, then if all appears well down to 0.39 cal.

For those who haven't read the whole thread, I'm inducing spin in the forward section of the missile whereas the aft should nominally fly without rotation.
I feel some "test runs" in the car coming on with your arm out a window, preferably as a passenger! Unless of course you've got that wind tunnel set up that you once mentioned!
 

BrendanH69

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How does the booster factor into the stability during boost of the 1st stage? (i feel like I messed that from earlier in the thread)
The aft most booster in the photo is a modelling of the real thing’s tube launch “blip motor”, which is intended to just get it moving and out of the tube/off the rail with some decent momentum before the main booster/sustainer (called the “Bus”) ignites and accelerates away.

See earlier post nos. 9, 14 and 88.

The OR file I’ve built up assumes that it is part of the flight. The file suggests it doesn’t appear to affect stability margin too badly, probably because of the decent fwd weight of the Darts/Dart Carrier/Fwd Transition assembly. Stability is still about 1 Cal with it, 1.7 Cal without it. My only concern in the OR stability data is any potential effect of using odd tricks to model it visually, i.e. a phantom body tube for the narrower fin-can section.

It’s flight is very short lived and is intended to separate very quickly, therefore hopefully it’s not going to have too long an impact on stability. Initially I’ve included it in my build for completeness and just for show, however I’ve built it with the intention to be flyable later on.
 

OverTheTop

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Great to see you thinking about seriously about safety on this slightly unconventional bird :) .

Is there some way magnetic retention might help you out with this, perhaps to prevent drag separation?

I like the idea of tilt lockout and it is really a necessity IMHO for multi-stage flights, although you only have B motors on the darts so it might be not as necessary to prevent you breaking your waiver cylinder.
 

BrendanH69

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Is there some way magnetic retention might help you out with this, perhaps to prevent drag separation?

I like the idea of tilt lockout and it is really a necessity IMHO for multi-stage flights, although you only have B motors on the darts so it might be not as necessary to prevent you breaking your waiver cylinder.
I agree, OTT. If I was the RSO, I'd feel more comfortable knowing some tilt safety was built into the safety controls for this project. Even with low power motors, three pieces of streamlined gorgeousness free falling pointy end first from 600ft is non-optimal for the humans and bovines that share our launch site!

I've not had any experience of a magnetic retention type solution. My initial concern was more about the jarring g-forces flinging the Dart free during descent after a tilt-abort rather than just drag separation of the Darts after main motor burn-out & a tilt-abort, but I can see that both are relevant here.

Would magnetic retention be strong enough to resist the G-forces as the carrier/AV bay is deployed for the main chute and then under the irregular forces it might experience as it tumbles/descends? I'll have to make sure I get some measurements during the test flights with the Darts physically locked in place and then take it from there.

More discussions and consultation with the club RSOs required!
 

BrendanH69

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Oh yeah, almost forgot....first dart is 100% complete. Three interchangeable nosecones all weighted differently so I can test stability of the free-spinning canard segment at 1.1 cal, then 0.78 cal, then if all appears well down to 0.39 cal.

For those who haven't read the whole thread, I'm inducing spin in the forward section of the missile whereas the aft should nominally fly without rotation. This should effective reduce the impact to CP from the canards and simultaneously add gyroscopic stability to the rocket. Both of these things independently should allow a rocket to be acceptably stable below the 1.0 caliber rule-of-thumb.
Looking forward to some test flight results!

Maybe need some roll pattern on the body sections too, as well as the fins?

For comparison, my two Dart flights were with the same unit. Canards were fixed, bevelled symmetrically both sides and were not inclined to the airstream. GLOW was 130g incl. the C6-5 motor. This included 5g more trim weight I added to the nose cone the night before in addition to the 38g of weight I had previously epoxied into the tip of the nose cone, so total added nose weight of 43g. Stability margin was 0.7 Calibres, with CoG verified against the OR calculations.
 

neil_w

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This is a really interesting build, fascinating scale subject.

Do all three darts launch at the same time? I was thinking how cool it would be if they sequenced about .25 - .5 seconds apart.
 

DrewW

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This is a really interesting build, fascinating scale subject.

Do all three darts launch at the same time? I was thinking how cool it would be if they sequenced about .25 - .5 seconds apart.
@neil_w man this whole thing wasn’t complicated enough?!? Alright fine I’ll time phase release after I figure out how to just release. I think I can use a burn through thread as a retention device ( simple, cheap, and requires motor ignition) to prevent drag separation, then it’s just on the electronics for sequencing which given the correct selection shouldn’t be an issue.

I should probably start reading up on competition scale scoring 🤔
 

DrewW

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By the way, here is my gen 2 tower. A few tweeks still needed, I forgot to check my clearances when it was separated into pieces so I have an interference fit I'm not too thrilled about at the moment, but an easy reprint overnight...ugh.

Integrated rail system for mini rail buttons. Currently the features as I've arranged them don't match a final scale version. I'm not sure I'll be able to reconcile that, but I probably still have options to look into.

IMG_0075.JPG


IMG_0073.JPG
 

BrendanH69

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I think I can use a burn through thread as a retention device ( simple, cheap, and requires motor ignition) to prevent drag separation
Interesting, and possibly the simplest solution!
Would this be literally a length of thread under tension holding the back of the Dart to the carrier, waiting to be melted/burned through by the ignition of the Dart's own BP motor? Have you used that before Drew?
 

DrewW

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Interesting, and possibly the simplest solution!
Would this be literally a length of thread under tension holding the back of the Dart to the carrier, waiting to be melted/burned through by the ignition of the Dart's own BP motor? Have you used that before Drew?
@BrendanH69 So I've never done it before, but was just reading about it in Tim Van Milligan's (of Apogee Rockets) book "Model Rocket Design and Construction". I believe the reference was for boost and rocket gliders, where the burn through thread (plain sewing thread) is used to hold the spring energy of a few rubber bands back until the ejection charge burns through the string, thereby releasing the glider elements to reconfigure for a properly trimmed glide. I could see using the same method in some fashion to prevent drag separation without fancy magnetic interlocks or having to deal with shear pins.
 

BrendanH69

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By the way, here is my gen 2 tower. A few tweeks still needed, I forgot to check my clearances when it was separated into pieces so I have an interference fit I'm not too thrilled about at the moment, but an easy reprint overnight...ugh.

Integrated rail system for mini rail buttons. Currently the features as I've arranged them don't match a final scale version. I'm not sure I'll be able to reconcile that, but I probably still have options to look into.
Hi Drew, speaking of clearances, don't forget to allow for sufficient Carrier rail guide & Dart body-tube stand-off to ensure the tips of all those spinning canards on your Darts don't clash.

Looking at my fixed canards in position in my Dart Carrier, I estimate I would have to increase the offset of each Dart's centreline from the Carrier centreline by another 20mm to avoid rotating canard tip clashes if they were spinning from launch. This would likely push them outside the OD of the Bus, making a problem for future tube launching.
This makes me suspect that either the OD of the Dart Carrier is actually smaller than how I've made it (but I don't think so judging by the photo below), or that the canards may not spin until after Dart release from the Carrier and perhaps the mini clutch (used for guidance/steering) in each Dart fwd section is "released" to permit rotation only upon deployment from the Carrier.

1623647074844.png
 

BrendanH69

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@BrendanH69 So I've never done it before, but was just reading about it in Tim Van Milligan's (of Apogee Rockets) book "Model Rocket Design and Construction". I believe the reference was for boost and rocket gliders, where the burn through thread (plain sewing thread) is used to hold the spring energy of a few rubber bands back until the ejection charge burns through the string, thereby releasing the glider elements to reconfigure for a properly trimmed glide. I could see using the same method in some fashion to prevent drag separation without fancy magnetic interlocks or having to deal with shear pins.
This concept is growing on me as a safety option to discuss with the more senior club members.
Even if it needed to be stronger than cotton thread, tethers from each Dart could be fed back through the igniter "pass-through" holes at the base of the carrier to a single release mechanism inside the fwd transition or upper AV bay. Maybe even a BP cable cutter type device to sever them as part of the same Dart ignition circuit.
 

BrendanH69

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So I've never done it before, but was just reading about it in Tim Van Milligan's (of Apogee Rockets) book "Model Rocket Design and Construction".
Aaah, Tim! I've watched many of his educational videos and shopped in his on-line store many a time more than I care to mention! If it were up to me he should be given a knighthood for services to rocketry! Sir Tim Van Milligan! Got a nice ring to it.

Anyway I've been meaning to ask you, Drew - why the Starstreak and what has inspired to start this project?

For me, I grew up in Northern Ireland and was educated in Belfast in the mid to late 1980s where Short Bros. (now part of Thales) developed several air defence systems and the first version of Starstreak. Many of my university engineering classmates went on to work at Shorts and some were involved in early development and testing of Starstreak. So for me this is a bit of an homage to the technical skills, ingenuity and hi-tech capabilities of my countrymen and former classmates back in N.Ireland. It's also testing my build skills and a bit out of the ordinary too!
 

DrewW

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Hi Drew, speaking of clearances, don't forget to allow for sufficient Carrier rail guide & Dart body-tube stand-off to ensure the tips of all those spinning canards on your Darts don't clash.

Looking at my fixed canards in position in my Dart Carrier, I estimate I would have to increase the offset of each Dart's centreline from the Carrier centreline by another 20mm to avoid rotating canard tip clashes if they were spinning from launch. This would likely push them outside the OD of the Bus, making a problem for future tube launching.
This makes me suspect that either the OD of the Dart Carrier is actually smaller than how I've made it (but I don't think so judging by the photo below), or that the canards may not spin until after Dart release from the Carrier and perhaps the mini clutch (used for guidance/steering) in each Dart fwd section is "released" to permit rotation only upon deployment from the Carrier.

View attachment 468798
Great picture of the carrier @BrendanH69 !
So I'm also curious about the canard rotation/clutch system. From some of the photos of launch events, there never appears to be any blur about the canard segment which you would expect for a free rotating system, the canards are always crisp in the images....though under launch conditions they may be using high speed photography at 20,000 fps which would counter what I just said.

But from the lower bracket it appears the darts need to be throw away from the carrier, which may require booster fins to induce a roll event near burnout. This would create the outward force along with drag separation for the darts to clear the carrier.

As for the Carrier, it is wider at the bottom than at the top. The flat side in the image is a cut from one radius to another. I believe the black ring near the top of the carrier is the same OD as the diameter in the lower third.
 

DrewW

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Aaah, Tim! I've watched many of his educational videos and shopped in his on-line store many a time more than I care to mention! If it were up to me he should be given a knighthood for services to rocketry! Sir Tim Van Milligan! Got a nice ring to it.

Anyway I've been meaning to ask you, Drew - why the Starstreak and what has inspired to start this project?

For me, I grew up in Northern Ireland and was educated in Belfast in the mid to late 1980s where Short Bros. (now part of Thales) developed several air defence systems and the first version of Starstreak. Many of my university engineering classmates went on to work at Shorts and some were involved in early development and testing of Starstreak. So for me this is a bit of an homage to the technical skills, ingenuity and hi-tech capabilities of my countrymen and former classmates back in N.Ireland. It's also testing my build skills and a bit out of the ordinary too!
On my side, fair amount of interest in rockets and missiles from my time as an undergrad in the physics department. When COVID turned things upside down I took on building rockets with my kids; first air, then water, then Estes. After building the first 40 kits (between June and August) I started looking into other things, bigger (MPR & HPR) kits, then scratch building. Then came across an article about defense systems that included the Starstreak and was enamored by it's differentness, a real work of engineering. Started looking at who'd put one together and just kept seeing intent without follow through so I set the challenge for myself because its ugly, and elegant, and hard, and nobody else had done it.

I guess I just like things that are hard and different, because they're the most interesting challenges.
 

DrewW

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This concept is growing on me as a safety option to discuss with the more senior club members.
Even if it needed to be stronger than cotton thread, tethers from each Dart could be fed back through the igniter "pass-through" holes at the base of the carrier to a single release mechanism inside the fwd transition or upper AV bay. Maybe even a BP cable cutter type device to sever them as part of the same Dart ignition circuit.
@BrendanH69 I can confirm from personal experience of a failed scratch build, an Estes motor will burn through 100# Kevlar thread just fine. You could substitute anything less substantial (and easier to work with) and achieve the same result.
 

BrendanH69

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From the photo of the real thing you can see that there is a lanyard to each Dart running fwd from the three white plastic sabots. These appear to have pins and lock wire attaching to the section of each Dart just aft of the “canard-can”. At launch, these sabots quickly fall away and the lanyards release...something. It’s possible that these lanyards are either the firing sequence communications link from the operator to “fire up the gyros” as the Royal Ordnance video in post no.9 says, or they are a physical lock for the mini clutch steering system, or even both.

1623655702706.png



1623655777992.png



From the Royal Ordnance video in post no.9, the tube launch motor’s canted nozzles induce a 10hz rotation out of the tube. This then increases to 35hz, possibly under aerodynamic mechanisms as further nozzle canting in the Bus motor would have to be finely tuned and subtle given the very very very fast burn of that motor propellant. VMAX motors, eat your heart out!

In post no.86 the Thales video has lots of launch shots and slow motion video. Hard to determine, but I’d say that:
  • Sabot separation (and possible mini clutch release) is very early, before the Bus has even fully cleared the launch tube.
  • The video from about 42s in suggests that the even after sabot release, the canards appear to be only rotating at the same rate as the rest of the missile body assembly, at least until Bus motor ignition. Hard to tell as the footage isn’t long enough to say for sure whether the canards are spinning up.
  • If the canards do start spinning at sabot release, then I suspect that the high speed photography is masking the ability to determine this easily.

My best guess is that the Darts move away from the carrier into formation under a combined effect of the 35hz rotation and maybe a little extra kick they might get away from the carrier from the shear pin severing process at Bus motor burn out.
 

DrewW

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This is a really interesting build, fascinating scale subject.

Do all three darts launch at the same time? I was thinking how cool it would be if they sequenced about .25 - .5 seconds apart.
So interestingly, according to the NAR scale competition rules I would need to have a functioning BLIP motor to comply with rule 50.8 for scale, and rule 53.7 for sport scale. It also appears I would lose points in operating it as you suggest, for a non-mission representative deployment of stages.
 

neil_w

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Of course you are correct. I lost sight of the fact that this is a scale subject. Sorry for the digression.
 

DrewW

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Of course you are correct. I lost sight of the fact that this is a scale subject. Sorry for the digression.
Ultimately interesting because it actually caused me to read the rules and scoring. I’ve never gone the competition route before, but this would as you say make an interesting subject for scale
 

BrendanH69

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So interestingly, according to the NAR scale competition rules I would need to have a functioning BLIP motor to comply with rule 50.8 for scale, and rule 53.7 for sport scale. It also appears I would lose points in operating it as you suggest, for a non-mission representative deployment of stages.
Soo. .. I'm maybe not completely wasting my time building my Blip/tube launch motor! :p

However.... how does one score/judge a scale project for which there are no accurate/published reference drawings?🤔
 

PeterAlway

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Soo. .. I'm maybe not completely wasting my time building my Blip/tube launch motor! :p

However.... how does one score/judge a scale project for which there are no accurate/published reference drawings?🤔
This year's NARAM is Sport Scale. That event just requires photos (or a drawing) that clearly shows the overall shape of the rocket. No measurements needed. You will also need a legit source that explains how the triple upper stage system works (not the technicalities of how, but just what separates and how it would look) if you want the bonus Mission Points for staging. You don't have to create your own drawings, you just need to provide the same pictures you used to build it.

I'll point out that I'm finding it difficult on a superficial scan of this thread to figure out what's missile, what's sabot, and what's launcher, so you will want to make that clear. You don't need tons of detail photos, but you do need clarity, because the geometry of this contraption is not easy at first glance.
 

DrewW

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This year's NARAM is Sport Scale. That event just requires photos (or a drawing) that clearly shows the overall shape of the rocket. No measurements needed. You will also need a legit source that explains how the triple upper stage system works (not the technicalities of how, but just what separates and how it would look) if you want the bonus Mission Points for staging. You don't have to create your own drawings, you just need to provide the same pictures you used to build it.

I'll point out that I'm finding it difficult on a superficial scan of this thread to figure out what's missile, what's sabot, and what's launcher, so you will want to make that clear. You don't need tons of detail photos, but you do need clarity, because the geometry of this contraption is not easy at first glance.
Thanks for the input @PeterAlway . I've never taken part in the competitions before and really just started as a project for personal enjoyment and challenge. That said, any info on where this would face issues in judging and where the kinks need to be worked out are much appreciated.
 

PeterAlway

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Thanks for the input @PeterAlway . I've never taken part in the competitions before and really just started as a project for personal enjoyment and challenge. That said, any info on where this would face issues in judging and where the kinks need to be worked out are much appreciated.
I went back to the first two pages of the thread, and the photos on this thread contain everyting you'd need for Sport Scale data. Your do need to be careful to select and organize just a few (probably no more than 4 or 5, maybe fewer) of them for the judges. You have to give the judges a hard copy of your data (so get printouts ahead of time). Try to keep it under 3-4 pages if you can. Your model will be judged, not your Google-image Fu. Simple data is good, even for a complex model! Your judge wants to understand what your prototype looks like in 15 seconds. Then when the judge gets down to judging, they want to be able to answer the question "Does this model look like the real rocket?" in a couple of minutes without having to leaf through a whole book repeatedly.

Be sure to include one clear overall photo of the version and color scheme that you are modeling. Your model has to include the first stage to qualify.

If you want to include more photos to clarify details like the dart section, use photos of the same version/paint scheme. If you have to use closeups of a different paint scheme, or a closeup without a stage, make a note on the printout of the photo.

Don't worry at all about Ez2cDave's uncredited post of Vladimir Minakov's Nike Hercules drawing. You absolutely do *not* need to construct drawings like that to enter Sport Scale.
 

BrendanH69

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Thanks for the input @PeterAlway . I've never taken part in the competitions before and really just started as a project for personal enjoyment and challenge. That said, any info on where this would face issues in judging and where the kinks need to be worked out are much appreciated.
Interesting to hear. +1 on what Drew said.
 

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Don't worry at all about Ez2cDave's uncredited post of Vladimir Minakov's Nike Hercules drawing. You absolutely do *not* need to construct drawings like that to enter Sport Scale.
Peter, that would be the "late" Vladimir Minakov ( I doubt he's offended that I forgot to cite him ). Since ROTW 5 is coming out in the, hopefully, near future, are you planning to generate high-quality drawings, like those, for all prototypes, for Precision Scale ?

Dave F.
 
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