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DynaSoar

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I wanted to work on a design that I could test at each step as I scaled it up to HPR, keeping what worked, changing what was needed, and resulting in something capable of contest competition. I settled on a 3 tube cluster design, the entire airframe being the three tubes and nothing else. The fins attached to the tube joints so they'd have lots of area to bond to. The cross section of this design is 2/3 that of a single tube that could hold the 3-cluster MMT. To keep that cross-sectional benefit, it required some fancy balsa work. The end result so far is 3 similar airframes with 3 payload sections, using 3 different methods of 3-to-1 tube adapting.

These are, from left to right, Sandman, Mechtayu and Dreamcatcher.
 

DynaSoar

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The first one was Sandman, named for the very helpful rocketeer who turned the tube adapter for me, and painted to match the Sandman uniforms from Logan's Run.

The transition started as a BT50/70 adapter, with 3 sides sliced off, and with holes drilled into the bottom to fit the three BT50s. A small piece of said tube was glued in, and into which a length of coupler was inserted and glued. The couplers then mate to the main airframe tubes.

After fitting the parts, the adapter has hand carved (entirely by sanding) until it was a smooth, curved 3-to1 tube transition. Due to the tubes glued into the bottom, this design was the widest (ie largest cross section) of the three.

In all cases, one of the three mating points has the shock cord attached, the other two each connect to a chute. Each booster got a name tag of red painted on detailing tape.
 

DynaSoar

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It's Russian for "dream", specifically not the night time dream, but the "hope" or "desire" dream. The paint scheme is the Russian flag. I went this way because this design reminded me of Vostok. It was the cheap and dirty method of 3-to-1 tube mating: three conical nose cones with a 4th upside down and glued against the three. Lowest cross section of the three, but the hollow spot under the center cone looks like it will have some drag problems.
 

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The third design is Dreamcatcher, painted with the traditional Native American colors for the 4 races, the order of colors matching the American Indian Movement flag. The transition started out again as a BT50/70 adapter, but this time solid balsa bulkheads were glued to the bottom, and then everything sanded off until the smooth 3-to-1 transition came out. For this design I switched to epoxy, since the contact area might not be enough for wood glue. I also used epoxy on the tube and fin fillets (imagine 3 fillets, 3 feet long each) and basswood fins on the third airframe.
 

DynaSoar

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I decided that testintg required working with minimum weight, so I did up a nose cone to fit the airframes. This started out as a custom turned nose cone from Balsa Machining, an ogive 2.1 diameter by 10.5 length, one inch of length being cylindrical before the ogive started, and no shoulder at all. Again, solid balsa bulkheads were glued to teh bottom, and then the nose sanded into shape. Here it is on the Sandman airframe.
 

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Typical business end of an airframe. All three use E size engine hooks facing the center.
 

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To test the design up to high power levels required a booster stage. Here's the Dreamcatcher airframe with the plain nose, sitting on a 3-cluster booster stage that can fit any of the three. Side note: this airframe has no lugs. it's set up to fly from the tower I built.

HPR? Three Estes E9-0 boosters and three E9-6 sustainers, and this thing will be burning a total of 171 ns, 11 ns more than the "official" H engine power limit. Official certification rules say clusters can be up to 320 ns before being HPR, but then I'm testing the physics, not the cert rules.
 

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Having great belief in the ability of the design, I scaled down and did an 18mm version for LPR competition. Here's the airframe next to the 24mm plain nose.
 

Micromeister

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darn: your thread heading got my hopes up:( I just love night flight vehicles.. if flown under a full night launch FAA waiver of coarse.
Very nice designs Dyna:
would you expand some on the Physics your studying? Drag/transition effect?

Clustering is my second favorite type of flying, and Cluster/altitiude is my 3rd favorite competition, preceeded by Scale and PMC in that order:)

The Dreamcatcher transition is most elegant, very nicely done.
These all look like Excellant sport flying models.

Competition however? Looking at the 18mm model, I'm wondering what particular event you think this configuration my be competitive in? Do you plain on using a 24mm nose on the model?

Three motors Cluster altitlude event will be 3 - 1/2A (13mm motors) well, I guess it's possible to use 3 - 18mm 1/2A6-2 motors but the self imposed casing weight penelty would make this configuration pretty much useless. Add to that a huge diameter 24mm nose or shroud will drastically reduce possilble maximum altitude especially in this motor class.

Have you had a chance to flight test and track any of these designs? I'm sure you will see first hand how the various types of drag effect these designs.

For this motor class you may want to look at in-line body configurations. flight test have proven they out preform stacked tube models by a great margin. Here's a pic of a few of the 10 designs flight tested before NARAM-35 3x1/2A clu/alt. If I were flying 3x1/2A today it would be an even more elegant design. I'll post the 3x1/8A Micro-Maxx prototype in the next post.
Hope it's helpful.
Your group are very cool Cluster models though.
 

Micromeister

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Here's the Micro-Maxx version of the 3x 1/2A cluster/atitude 13mm model I'd be flying in competition today. Note the taperered pod in-line construction and 3 fin design which further reduces several points of drag. I've almost lost this model on 3 - 1/8A .21n/sec Micro-Maxx I motors. it's out of sight very quickly;) saved by the orange streamer..
 

DynaSoar

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Originally posted by Micromister
darn: your thread heading got my hopes up:( I just love night flight vehicles.. if flown under a full night launch FAA waiver of coarse.
Very nice designs Dyna:
would you expand some on the Physics your studying? Drag/transition effect?

Clustering is my second favorite type of flying, and Cluster/altitiude is my 3rd favorite competition, preceeded by Scale and PMC in that order:)

The Dreamcatcher transition is most elegant, very nicely done.
These all look like Excellant sport flying models.

Competition however? Looking at the 18mm model, I'm wondering what particular event you think this configuration my be competitive in? Do you plain on using a 24mm nose on the model?

Three motors Cluster altitlude event will be 3 - 1/2A (13mm motors) well, I guess it's possible to use 3 - 18mm 1/2A6-2 motors but the self imposed casing weight penelty would make this configuration pretty much useless. Add to that a huge diameter 24mm nose or shroud will drastically reduce possilble maximum altitude especially in this motor class.

Have you had a chance to flight test and track any of these designs? I'm sure you will see first hand how the various types of drag effect these designs.

For this motor class you may want to look at in-line body configurations. flight test have proven they out preform stacked tube models by a great margin. Here's a pic of a few of the 10 designs flight tested before NARAM-35 3x1/2A clu/alt. If I were flying 3x1/2A today it would be an even more elegant design. I'll post the 3x1/8A Micro-Maxx prototype in the next post.
Hope it's helpful.
Your group are very cool Cluster models though.
Well, the name came about because I named the first one for Sandman, who turned that transition for me and helped with the mating design. I just carried on with the night/sleep idea after that.

I *am* looking for some strong clear tubes for flying strobes for night flight. White LEDs are bright enough now and low power enough.

I'm also waiting on some thin-film solar panels to experiment with powering electronics off them.

I'm looking at which transition has the least drag (cross-section and drag characteristics), but also testing their integrity, including glues. Frinstance, would the 4-cones transition stand up to equivalent of H power, with a payload vibrating above it? Same with the various fins. I'll probably end up with some destructive testing, but I'm trying to squeeze all I can out of LPR techniques rather than just assuming mid and high power require extensive changes. Sure, I'm out voted by 20 years of HPR flyers. But I'm a scientist -- can't tell us nuthin, we got to see it ourselves.

I am looking at cluster altitude with the 18mm at least. Three AT D21's would put it in the E engine equivalent category. There's no cluster altitude records for Class C (adult) above engine class C. The trick will be getting it back. For the nose, I'll be doing the same carving down of a nose and gluing od blocks or couplers, for a BT60 size this time.

I'll defininitely look into in-line vs. stacked, thanks. I can't see why an inline would be better yet, but as I said, I rely on data. Perhaps stacked isn't optimal for contest. Still, competition is secondary here. The whole project began in order to scale up the design and test the various technologies in real comparisons. I want to build the best by finding out what's good enough rather than going for what's better is some respects, but probably not in others (ie. total weight of glue used of wood glue vs. epoxy. Sure epoxy is better, but do I end up using twice the weight and overbuild, when half the weight of yellow stuff would be adequate?).
 

Micromeister

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For night flying payload tubes you can buy clear and/or red tubes for both Estes and Quest I seem to recall them in BT-5, 20, 50 and even BT-60. I buy 48" long Clear Polyethylene mailing tubes in sizes from .28" to 2.55 ID. which is a very nice Bt-80 match.
We've been flying strobes, Leds and other devices in modes from micro-Maxx to 5 D12 clustered an d G80 powered models since about 1990. alway with a full FAA waiver. No model rocket can be flown between sunset and sunrise. our 1LB exemption does not apply to flying after sunset not dark.

As I mentioned I've been doing an ongoing R&D on Cluster/Altitude project since Perp for Naram-35 in 1992. expeiments and flight testing all along the way. may of the designs were simply outragious, but the were all evaluated and flight tested with multiple flights, tracked and closed within 5% to be included in the data. I'm not sure which types of drag your looking at but as many a 4 different specifice drag factors are involved. Actually in-line appears to provide better lineal flow then the stacked method. I'm not quite folloing your asertion on transition strength.. I do not fly APCP unless forced. I'd rether cluster D12's then fly a single G motor, OBTW HPR isn't even close to 20 years old 13 oir 14 at the very oldest, I look forward to seeing what your experiments come up with, thou I'm still a little fuzzy on exactly what your trying to test.

You mentioned in one of the pervious posts your "downscale" to 18mm was for cluster altitude competition.. I can only assume from your answer you don't have a U S sport rocket Code (The Pink book).
Cluster altitude is a progressive total impulse and number of motors event ending a 6xC because 7 D12 oe D21's will exceed the 125g model rocket propellant limit. The events as they stand
are 2x1/8A Micro-Maxx (proposed), 2x1/4A, 3x1/2A, 4xA, 5xB and 6XC so 3 D21's has no contest impulse motor combination level in which to fly. I can for sure let you know 6xC cluster altutide has been flown and recoverd from 2185 feet within 20 yards of the launch site. I don't think 3 D21's would be much of a problem.
As far as stacked to in-line I'd think altitude is the way you'd judge optimal configuration. which has nothing to do with competition, but everything to do with aerodynamics.including finish, streamlineing, Optimal mass motor selection and of course good tracking. I you plan on using scientific method look at your parameters closely before being data collection.
Hope this helps a little.

PS
A while back we had a pretty indepth thread on Night Launch vehicles in the low power section If you do a search on Night Launch it should come up... It's loaded with info on LED and other Night Illumination Tracking Equipment (N.I.T.E.)systems.
 

Stymye

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hey Dyna,
I like the simple ,yet high visability paint jobs
that should help out any observers with tracking !

Micro ,you never cease to impress me with your knowlwdge across the board, concering so many aspects of rocketry!

great thread and lots of pics
I must say that at first, I was expecting to see a bunch of
"lit up" rocket pics but ,it turned out to be just as interesting anyway
 

Micromeister

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Stymye:
you know if ya stay at anything long enough even a blind horse gets on the trail once in a while;)

Heres another group of Cluster/altitude models these are left to right 13mm with the blue one on the far right a 10.5mm that briefly set a Team nat'l record at 371m (1217feet). Man I miss those 10.5mm motors:D
 

Micromeister

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Dyna:
Heres a close up of the 4 tube transition and pods, May help explain the "slippery" tapered pod theory. the brown stuff on the center tube and elsewhere is mud from the recovery field. Sorry I should have cleaned it up before taking that pic.
 

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Belching burning BP from all three tubes, wearing its payload section. Sadly, yet another chute problem (3 in a row) bought it down on hard ground and snapped a fin a 1/3 of the 3-to-1 transition. But MAN did she fly.
 

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Dreamcatcher 2 is ready to fly.

This time the airframe is heavy wall, foil lined 24mm tube. The fins are carbon covered 1/16th 3-ply birch with JB Weld fillets the lower 12", to handle the motor and ejection heat (90 minute epoxy the remainer). Motor blocks are set to 7" to handle Ellis Mountain's long 24mm G37s. Positive motor retention is by a single threaded rod embedded in JB Weld between the tubes, with a washer and nut threaded on after the motors are inserted. Weight before motors is 14 ounces, subsonic average cD = 0.512.

Flight testing will be done on E9-8s since I know how it should act on these. Projected altitude is 2000'.

Projected altitude on Ellis G37s (total impulse 331.5 Nsec; 3.6% I)is 8490', speed Mach 1.2 (max Q at Mach 1.05, cD 0.71).
 
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