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  #1  
Old 08-09-2009, 07:57 PM
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blackshire blackshire is offline
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Default *Tethered* rocket glider (a new concept)

Hello All,

A very fertile-minded Frenchman named Eric Brasseur has thought up, described in detail, and experimented with several unusual aerodynamic concepts (see: www.4p8.com/eric.brasseur/index.html#glider2 ). He has devised a most unusual aerodynamic decelerator device, called a "Linked Samara Decelerator" (see: www.4p8.com/eric.brasseur/ropar.html ), that can be used instead of a parachute to lower a load to the ground safely. A plank-type (un-swept, that is) tailless glider or a swept flying wing glider would be ideal for use as the main component of this device, and neither type of glider would even require vertical tail surfaces for this application!

The Linked Samara Decelerator is nothing more than a small, simple glider (it is of conventional configuration in his conception) that is linked to the load by means of a long cord that is affixed to one wingtip of the glider. This load/cord/glider arrangement looks like that of a tethered "round-the-pole" powered model airplane or a single-cable type U/C (U-Control) powered model airplane. For model rocket use, the glider (an un-swept plank tailless would be ideal) would fit inside the body tube and would be expelled at ejection. Since no components of the model would be jettisoned to fall separately, this would make it a rocket glider (RG) rather than a boost-glider (B/G).

The glider flies rapidly in circles around the load (the load also rotates in a smaller circle about the system's center of mass) as the system descends, which creates a virtual flat ring drag surface whose width is the same as the glider's wing span. This is analogous to the virtual rotor disc surface that is described by the rotating rotor blades of an autogyro, gyroplane, or helicopter. The Linked Samara Decelerator has a very low opening shock because it takes the glider a few seconds to "spin up." Also, the drag coefficient (and thus the descent rate) of the system can be varied by reeling in or paying out more of the line, which changes the glider's rotation radius and speed. The system can even be steered by utilizing movable control surfaces on the glider. Using a plank-type or swept flying wing glider would greatly simplify the Linked Samara Decelerator.

I hope this information will be helpful.
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Last edited by blackshire : 08-09-2009 at 08:03 PM. Reason: This ol' hoss done forgot somethin'.
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Old 08-10-2009, 08:10 AM
lessgravity lessgravity is offline
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This is a very interesting concept. I could see many ways to apply this to a rocket/glider recovery. This might be something that would be fun to test. When i get some time I may try to come up with an application.
The easiest application I can see is simply a glider using a boost pod as the load. Thus recovering in one piece.
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Old 08-10-2009, 12:12 PM
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It shouldn't be hard to make the engine pod on a "swing arm" that would act as a weight (with the engine still in it). It would come down just like a "helicopter seed" from a tree.
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Old 08-10-2009, 02:58 PM
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I think both of those approaches (a rigid "swing arm" as well as a flexible cord) are workable. Due to the similar masses of the typical glider and its pop pod, the system would rotate around a center of mass that would be near the geometric center of the system (like a double star system in which both components orbit about a point in space between them that is the star system's center of mass). This would actually be an advantage, because the whirling pop pod would also contribute to the system's drag as it descends.
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Old 08-24-2009, 12:21 PM
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As far as NAR competition rocket gliders I think this type of recovery would not be allowed unless the rotations were very slow and wide. For contests a glider must glide, not just go into a flat spin.

Novel, and interetersting, but more of a gyroc/heli descent than a glide.

kj
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Old 08-24-2009, 02:38 PM
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A flat spin is when an aircraft rotates around a point (its center of mass) that is located inside the aircraft. An aircraft in a flat spin isn't flying, but falling. In the Linked Samara Decelerator, the glider/cord/load system rotates about the system's center of mass, which is well outside of the glider's body. Its glider is gliding (not rotating in a flat spin and falling), and its direction is simply constrained by the cord and load.

Regarding this recovery system's status with respect to NAR competition, that never even entered my thoughts. Most of us will never (due to lack of interest and/or money, or our geographic location) fly in a NAR competition of any kind.
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Last edited by blackshire : 08-24-2009 at 02:45 PM. Reason: This ol' hoss done forgot somethin'.
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Old 08-24-2009, 05:16 PM
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I think it was brought up more as a nifty idea. If it works, I think it would be good to limit the amount of field it takes to come down. Might even work in a school yard.
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Old 08-24-2009, 07:19 PM
shockwaveriderz shockwaveriderz is offline
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sounds sorta like control line rocketry... I beleive at one time they even had control line jets.

Missiles and rockets like the Hellfire(Ithink) have a kinda "spool" that lets out fine control wires as it fires away from its launcher.... I don't see why you couldn't do that with a modle rocket or HPR. With kevlar, vectren fibers or .004" stainles steel wire it could be made to work.

Afterall, the Estes model rocket cars used a straight line tether..... they could have gone round and round in circles if staked from one end.....

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Old 08-24-2009, 08:53 PM
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Yes, I suggested the Linked Samara Decelerator merely as an interesting variation on the existing model rocket recovery systems. (A local radiosonde weather balloon "flyer/data collector" of my acquaintance, however, is interested in the potential of this system as a possible replacement for radiosonde parachutes for some applications.)

Many years ago, I once made a sort of rocket "monorail." I taped soda straws to 18 mm motors and fired them down a string stretched tightly across the yard between two fences. Not having to fight gravity as they normally do, those motors moved VERY fast!

Another interesting application for model rocket motors (especially plugged motors) would be as powerplants for "round-the-pole" tethered jet planes. Jetex powered tethered jet planes often reached speeds of up to 200 miles per hour, and flying them indoors (not something I'd recommend with rocket motors due to the smoke and flames) was a popular club activity in the 1950s.
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http://www.lulu.com/product/cd/what...of-2%29/6122050
http://www.lulu.com/product/cd/what...of-2%29/6126511
All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com.
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Last edited by blackshire : 08-24-2009 at 09:06 PM. Reason: This ol' hoss done forgot somethin'.
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  #10  
Old 08-25-2009, 04:10 PM
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Quote:
Originally Posted by blackshire
Regarding this recovery system's status with respect to NAR competition, that never even entered my thoughts. Most of us will never (due to lack of interest and/or money, or our geographic location) fly in a NAR competition of any kind.


But competitors often look outside of the usual for inspiration. One example of that is the backslider RG idea that eventually was granted a patent.

I can't tell you the number of times I've adapted or adopted techniques from other aeromodelling disciplines to rocket flying, sport or contest.

I guess a video of one of these systems in action would help determine if it's gliding, or just falling vertically with a a winged surface rotating around it. By it's description it reminds me a lot of a glider with a drop weight dethermalizer attached at a wing tip.

kj
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