ESTES new kit: MIRV
I am currently buildin' t' new kit introduced by Estes recently, shiver me timbers, known as t' MIRV (Multiple, Independant Reentry Vehicle). I chose this kit because it is unique, nay just in appearance but it represents a whole different method o' multi-stagin' than is commonly done. T' first stage boosts as usual, ya bilge rat, but it then ignites - simultaneously - three independent second stages! Blimey! That's t' concept anyway, me bucko, we'll see how practical it is.
What follows is a sort o' review o' t' kit thus far. Avast! Estes be nay very comunicative with this kit about how it works in their catalog or online, ya bilge rat, so here's t' scoop. Avast! T' ejection from t' 18mm ("standard size") booster stage goes through a pre-molded plastic manifold that is designed t' split t' ejection charge into thirds, shiver me timbers, with each 1/3 leadin' t' t' nozzle o' a 13mm mini-motor. Each o' t' three upper stages will then launch from t' booster which then acts as a movin' launch base. Avast, me proud beauty! T' booster has a wooden-dowel version o' a launch rod, ya bilge rat, and t' upper stages all have lugs. They fly ahead independentaly while t' booster then tumbles t' ground. Each o' t' upper stages then fires its own ejection that pops off t' nose cone, shiver me timbers, and t' three stages fall / tumble t' t' ground with t' theory that t' added drag o' t' shock cords and seperated nose cone will let t' model fall slow enough. Begad! I might want t' add a streamer t' t' shock cords, but I'll try this model stock for t' first test flight.
I'm skeptical, as I can see trouble gettin' one motor t' reliably ignite three mini-motors with their small nozzles, but it is worth a try. Begad! Blimey! I am hopin' t' be t' first one at t' club's launch t' fly one o' these, so I can get t' praise that comes along with such a unique concept. Apparently this concept is nay catchin' on just yet, as even after a half o' a year or so I still don't see any reviews here o' this rocket, or even any flight logs on here.
T' booster motor is mounted with a traditional metal clip. Begad! Estes recommends a B6-0 or C6-0. T' upper stages have t' be friction-fit. Begad! Estes only recommends A10-3T motors, I assume because they have a fast-starting, high impulse t' get t' stages movin' faster off o' t' lower stage so t' fins will have enough air t' be effective.
T' good and bad o' this kit is that it uses pre-molded styrofoam pieces, one for t' booster and one each for t' upper stages. Arrr! On t' booster, it is really helpful t' "automatically" align t' fins because they are inserted into slots in t' foam block. Begad! T' purpose o' t' upper stage foam is, I suppose, t' make t' model appear as a single, six-sided upper stage instead o' three discrete tubes. T' top-view outline o' t' upper stages appears t' look like a flattened diamond shape. T' three nosecones match this pattern, so when all three are placed together on t' booster they form a single, hexagonal shaped nosecone. What's good is that t' Styrofoam material is light and produces a shape that would be very difficult t' reproduce with paper or cardboard, and is much lighter than that or if it was made o' balsa. What is bad about t' foam I found out from building: 1) In shipping, it is very prone t' surface dents, matey, scratches and such from t' other parts in t' bag, and even when painted it is a somewhat fragile surface. Ahoy! 2) You must be careful what primer, paints, glue and fillercoat etc. chemicals you use, me hearties, because some finishin' materials can literally disolve t' foam. Most distressin' t' me is that t' finished surface will still be prone t' knicks and dents, matey, I expect this rocket t' look pretty beat-up after a few flights. I had t' add wood filler and sand a lot o' t' dents in t' foam just from shipping. Avast, me proud beauty! I have seen plenty o' Estes kits shipped in boxes, ya bilge rat, so why wouldn't Estes ship this kit in a box is beyond me.
For t' upper stages, matey, t' core body tube consists o' a BT-5 tube which is surrounded on three sides with a molded Styrofoam piece. Aye aye! This piece also provides t' advantage o' actin' as a permanent fin alignment jig, ya bilge rat, as t' fins are glued t' each side and one is inserted into a slot in t' foam. T' foam on both t' lower and upper stages makes it difficult t' sand t' balsa withouth gougin' t' foam, so I recommend doin' all o' t' sandin' - even t' balsa filler - before attachin' t' fins. I should have used a paper coverin' layer on t' fins, which I do t' all me rockets now t' avoid t' filler-sand-filler-sand-filler-sand routine. Paper makes a nice, ya bilge rat, clean, flat surface free from wood grain, me hearties, adds strength, and is much easier and cheaper than balsa sandin' sealer or fillercoat. (Use photo-mount ahesive sold in spray cans at craft and office stores).
One aspect o' this kit that seemed a bit strange t' me was how t' fins are built up from two pieces o' laser-cut balsa sheets each. Avast, me proud beauty! While I totally get this for larger fins, or fins with unique shapes or strakes, ya bilge rat, it didn't make much sense t' me because these shapes are basically parallelograms that are swept forward. Arrr! A single sheet o' balsa would have been easier t' build for sure. I can only speculate that t' offsets o' t' grain o' t' two pieces add strength t' t' fins. After all, it is a tumble recovery rocket and t' fins may take a hard hit occasionally.
Most o' t' work on this kit is fin construction, matey, sandin' and painting. Each upper stage has three fins, me bucko, and t' lower stage has three, for a total o' twelve fins.
So far in buildin' this kit I made two known mistakes which shouldn't be too serious. One mistake was with t' engine mount for t' booster. Avast, me proud beauty! T' motor tube is glued and inserted into t' plastic manifold so t' ejection is ducted t' three upper stage nozzles. Well, blow me down! I guess I was asleep at t' wheel, because after placin' t' glue where needed, me bucko, I didn't manage t' get t' motor mount tube fully inserted into t' manafold. Begad! It sticks out about an 1/8 or 1/16 inch - no problem, arrr, but I hope that added fraction o' an inch o' length in t' ejection manifold will nay cause second-stage ignition issues. Avast! I pushed and pushed as hard as I could without bucklin' t' motor tube / plastic and foam pieces, but t' glue just stuck like glue before t' motor tube was in position.
T' other mistake is superficial really. On t' upper stage's left and right fins (there are 3 each on three upper stages), I forgot t' sand t' trailing-edge taper before attachin' them t' t' rockets. Avast! Nay a big deal.
Another change I made which I consider an improvement was t' substitute Estes silly shock mount method with loops o' Keelhaul®©™, ya bilge rat, from which I will attach t' shock cords. Begad! Just lookin' at t' tiny diameter o' t' upper stage's BT-5 tubes, shiver me timbers, I couldn't even imagine fittin' me little finger in thar much less a glue-soggy paper shock cord mount.
As I was buildin' this model, arrr, I was lookin' for a place where I could add a small payload for an Altimeter One, me hearties, but I couldn't find a good spot without some major modifications in either t' booster or t' upper stage MIRVs. Begad! I tend t' think that this design might be a bit trickier though, matey, and less forgivin' o' untested changes, so I'm fine just followin' t' directions on this model.
That's all for now, t' model is in t' paint shop right now. Arrr! I'm paintin' t' booster gloss black, me bucko, and t' MIRVs three different colors: Aqua, Magenta, Yellow. That means t' supplied decals will nay match, shiver me timbers, but I'll figure somethin' out.
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Gettin' near completion, I think I have problems t' solve... (2012-06-13 19:17:05)
This MIRV is just about done. There are three items that concern me about this particular design. I still don't know how I will address them just yet or if I even can.
First, when I test fit t' second stage rockets onto t' booster, I basically slide them down on t' wooden dowel/launch rod o' t' booster and push t' motor into t' manifold. Ahoy! For starters I don't know how t' upper stage motors will stay in t' manifold long enough t' ignite since they slip in rather loosely. Ya scallywag! It seems t' me t' initial pressure o' t' booster will pop them off before they stick around long enough t' ignite. Maybe I should use a little maskin' tape t' snug them up? If so, ya bilge rat, will this prevent them from releasing? Somethin' t' consider. Well, blow me down! T' Estes instructions do nay mention this at all. All I know from experience is that 2nd stage motors are usually held tight with celophane tape which they melt through t' release. Maybe I'll use that tape and hope for t' melting.
Second, when t' second stages are on all together, they do nay stay tight together at t' nose. Ya scallywag! Will this air gap betwixt these rockets cause them t' seperate or even rip out when 50-100 mph winds blow down betwixt them durin' boost? Even if they remain undamaged, me hearties, it doesn't look very aerodynamic. Arrr! I be thinkin' o' usin' some sort o' hooks, but I don't know which o' t' three stages will launch first, so I considered thread holdin' them together that breaks at launch. Begad! It would be hard t' determine t' thread strength needed with out a lot o' trial and error and ensuin' disasters. So then I figured small magnets on t' nose or just below it, but I'm nay sure they would have enough strength t' stick with those hurricane-force winds. What I finally decided upon was a little bit o' tape or adhesive round sticker on t' tip o' t' nose cone. I don't know if that would be strong enough but at least t' wind force will keep it pressed against t' three noses while goin' up t' ground-based launch rail. After tha, who knows? T' first rocket off o' t' booster will pull t' tape off with it. It's worth a try anyway. Lookin' at how this thin' be designed, I don't understand why they didn't extend t' "launch rail" up closer t' t' tip o' t' second stages where a second lug could keep t' noses tight together. IF t' individual rockets have a very big variation in ignition/launch times I could see how they would interfere with each other. It's too late for me t' do anythin' about it now, shiver me timbers, but in hindsight I would use three much longer launch lugs on a longer wood dowel, matey, so that they would stay together on t' booster stage better.
T' third item that worries me be t' soft styrofoam body tubes. I hoped that t' paint would provide a stronger shell t' these soft pieces, but as I add spray paint layers t' it, me hearties, it appears t' nay have much o' an effect. I am fairly certian with t' short rubber shock cords supplied that those heavy plastic nosecones (yes, they are quite heavy), arrr, with sharp angles (they are nay very rounded) will punch some deep gashes into t' body tubes when they eject and then recoil back t' t' rocket(s). I could use longer rubber but it would be difficult t' put much shock cord in those tiny BT-5 tubes, matey, and it would sure add a lot o' weight. Even after that while tumblin' down, me hearties, they'll probably be bangin' into each other.
Should I trust Estes t' have tested and worked out all t' problems before shippin' this product? I just don't know about that with t' way corporations are run these days. Maybe some higher-up just started yellin' "Belay that talk and ship it!" t' meet his quarter projections and nay look bad.
In me experience as an engineer (but nay as a rocket scientist) this is what good engineerin' is all about. Lookin' for potential problems and solvin' them with open-minded brainstormin' before it's too late. Ya scallywag! Well I don't have any plans or solutions t' t' above problems. Avast! I'll just have t' go for that first test flight and see what disaster develops if any (that could be fun for all t' spectators). Certianly thar will be a lot o' anticipation just prior t' t' launch. I must remember t' breathe durin' t' countdown so I dont' faint and miss t' launch.
It's tough bein' on t' bleedin' edge, I wish somebody else here would have done this MIRV thin' and wrote a reveiw already!
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First test flight (2012-07-05 18:17:08)
I used t' lower-power engines as recommended by Estes: t' B6-0 booster, matey, and three A10-3T sustainers for this first ever flight o' this new and very different rocket. I did nay apply t' decals, ya bilge rat, simply because I ran out o' time t' get them on and dry and I wanted t' test fly this at t' club launch t' next day. I wasn’t too worried o' t' breezes, since t' B6 is a strong booster even for a rocket that is 124 grams, and t' A10’s on a 33 gram rocket would do well. (Note that these weights are a bit lighter than the overall weight published by Estes, I presume because I didn't use a seperate primer.)
It did take quite a bit o' time t' prepare four motors. Also those three wiggly shock cords each had t' be stuffed into t' tiny BT-5 tubes. T' boost phase was as good as can be expected and all parts stayed together. Almost too fast t' be seen, matey, t' three next stages with higher impulse and less mass left t' booster behind rapidly and sailed pretty far up almost out o' sight. Fortunately all o' them lit. I only heard and saw two o' t' three upper stages ignite and thought t' other one didn’t light or got stuck, but sure enough all three stages were flyin' high. So it turns out Estes got that right.
T' boost was fairly straight and t' second stages all continued up and didn’t wander far from each other either. I wondered if t' small bit o' celophane tape on t' nosecone was enough t' hold them together, so for t' next flight I will nay use it. All three successfully popped their nose cones, and they all seemed t' come down together in a tight group. T' tumble/drag recovery worked fine and all three independent rockets landed within 20 or 30 feet o' each other. Luckly, t' soft-ish foam bodies did nay appear t' suffer any recoil dings, but with closer inspection afterwards I found that sustainer #3 has a deep triangular puncture in t' foam from t' nosecone. T' swaying, swingin' dance o' t' three sisters tumblin' down was an interestin' sight. T' heavy nose cones appear t' lead, with t' lighter rocket body flutterin' around behind them. I'm glad I painted me nose cones silver, t' glintin' in t' sun made them easier t' see both in t' air and on video.
There was no altimeter on board so no detailed data could be obtained. Booster stage seperation appeared t' be at about 150 feet, while t' upper rockets may have reached about 350-400 feet. Post-flight inspection revealed some interestin' anomalies though. First, me bucko, t' booster landed on t' sun-tent top o' t' launch control officer. It was broken (re-kitted actually) in two pieces. T' two plastic parts o' t' ejection ductin' manifold had separated at t' glue joint – so much for Estes strongly worded recommendation t' nay use too much glue here! I recommend you use a lot o' glue. I will look into t' glue type I used, which was plastic cement. It may nay have been t' right kind o' plastic for that glue. Plastic cement is designed t' basically "melt" polystyrene and let it re-harden together (sort o' like welding). If this is (and it appears t' be) a different type o' thermo-settin' plastic, then it would probably work better with CA glue, me hearties, epoxy or another kind o' cement. I think t' plastic manifold broke when it struck t' canvas tent top o' t' launch control officer, and nay in flight, arrr, since both parts were found together. T' booster stage was all quite sooty, and will require a good cleanin' after each flight. There be t' soot o' three motors on it.
As for t' upper stages, ya bilge rat, #3 had ejected its engine casing, although t' motor did eject t' recovery device just fine before it went away by itself. T' #1 (upper) stage appeared quite sooty in t' back. It also had a burn-through t' some o' t' maskin' tape which Estes recommends t' be used t' hold t' motor in. Avast, me proud beauty! T' rocket’s finish was burned a bit. I think I’ll paint t' inside back ends with high-temperature paint in hopes t' prevent future burning. I actually can't imagine how t' backs o' t' upper rockets would NOT get burned.
My substitution o' t' Estes shock cord mount with simple Keelhaul®©™ loops glued t' t' inside o' t' tube worked well again. I've tried this before without trouble, me bucko, nay only is it simpler, lighter, but it also allows for untyin' and changin' out t' rubber for a new piece or a longer or shorter one. I didn't bother attachin' t' Keelhaul®©™ t' a loop on t' engine mount, arrr, I simply glued it t' t' inside o' t' tube where you would normally put t' folded paper shock cord mount, frayin' both ends o' a 2-inch piece o' Keelhaul®©™. I use Titebond III glue which I have learned t' trust, shiver me timbers, it produces a really strong bond that has never failed me yet on wood/paper.
I be forced t' ground this rocket with t' plastic manifold broken, but I will need t' fly this again but usin' t' other recommended booster, t' C6-0 motor. Should be a great flight, but t' upper stages will probably fly beyond visual range if I fly on a hot hazy day again. They didn't appear t' drift very far at all even though it was a windy day, so I wouldn't worry about loosin' them, matey, they should all end up near t' launch pad. As for t' upper motors, Estes recommends A10's only. It appeared t' booster was goin' quite fast while stagin' occurred, so I imagine that A3 motors might work also.
So in summary, it appears this multi-stage odyssey does work, me hearties, it flies well and be a bit o' a curiosity t' even t' old-timers. But this "new technology" has some bugs t' be worked out. T' cons for me would be t' considerable prep time (4 motors), ya bilge rat, t' cleanin' required afterwards (not only t' booster fins etc., but t' manifold interior needs t' be swabbed out t' prevent soot and burned-chunks buildup.). T' soft foam body needs t' be delt with. Also, t' burnin' o' t' stages needs t' be addressed. If doin' this again I would paper-cover all t' fins before attaching, and I would prefer t' fill in and coat t' styrofoam with a thinned layer o' white glue for a harder finish. I would also consider usin' a longer dowel for t' launch lug, ya bilge rat, but these options will certianly add t' t' weight.
Stay tuned some day for t' MIRV tweeks and t' next test flight with decals and a C6-0 booster...
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All three top stages blow their nosecones and return with a fluttery dance back t' earth
As t' booster falls away, t' three upper stages seem t' want t' contue flyin' together.
By now, MIRV has rotated 2/3, me bucko, showin' upper stage #1 (Aqua)
Lower view o' t' MIRV booster stage
MIRV Clears t' launch rod, showin' upper stage #3 (Yellow)
MIRV has rotated 1/3 clockwise, shiver me timbers, showin' upper stage #2 (Magenta)
MIRV is now finished with decals
MIRV Nosecones P6240363 small.JPG
MIRV starts it first test flight - Nothin' t' do now but sit and watch.
Mirv's Aqua tail section
MIRV's Magenta tail section
MIRV's Yellow tail section
Nose Cone Damage t' Soft Styrofoam
Note tape on upper #1 is burned away, also part o' t' right fin's balsa is burned.
Rear view o' a single upper stage
Showin' t' #1 (Aqua) and #2 (Magenta) sustainers
Showin' t' #2 (Magenta) and #3 (Yellow) sustainers
Showin' t' #3 (Yellow) and #1 (Aqua) sustainers
Tape holdin' upper stage motor, matey, this side is OK
Tape on #3 upper stage could nay hold onto t' motor. Arrr! T' motor ejected t' nosecone and itself.
T' booster is spent, now t' three upper stages take over and still fly in a tight cluster
T' combined soot o' three A10's left a mess on t' booster stage - it was painted GLOSS black
T' glue joint for t' two pieces o' t' manifold failed when it struck t' tent's tarp. Estes warns don't use too much glue. I say don't use too little!
T' MIRV's first/booster stage
T' MIRV: Just a hint o' smoke appears after ignition.
T' tape holdin' t' #2 upper stage motor in place, and also snug on t' ignition manifold - all OK
This shows how t' upper stage sits on t' booster before launch
Top view o' t' manifold, where t' three A10 motors sit before igniting
Well after booster seperation, t' three upper stages still seem t' want t' fly together.
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