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  #11  
Old 04-18-2012, 07:28 AM
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blackshire blackshire is offline
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Default *Scale* conical lifting body boost-gliders!

Below are links to information on two subjects for *scale* conical boost-gliders that would fulfill your needs (having low lift/drag ratios, so that they wouldn't glide beyond the boundaries of your flying field). Axisymmetric conical gliders such as these would fly best with an offset Center of Gravity (with the CG not in line with the centerline axis, but to one side). To more easily trim such models for good gliding characteristics, the trim ballast could be movable, capable of being slid forward and backward in a track and then being locked into position with a set screw.

As the Centuri Technical Information Report TIR-24 "Model Rocket Lifting Bodies" that Doug posted in Reply #3 above shows (see: http://sargrocket.org/Documents/Centuri/tir-24.pdf ), the offset CG gives a conical lifting body the proper pitch trim to provide aerodynamic lift for gliding, and it also provides the analog of dihedral in the wings of a conventional airplane (the triangular cross-sections of conical model rocket lifting bodies such as the X-24 Bug and the HL-20 provide actual dihedral). Also, space capsules that could/can maneuver during re-entry such as Gemini, Apollo, Soyuz, Zond, and Dragon also had/have offset centers of gravity to provide lift. Here are the links:

[1] The BGRV (Boost Glide Re-entry Vehicle, see: www.astronautix.com/craft/boohicle.htm and www.daviddarling.info/encyclopedia/B/BGRV.html ) was a test vehicle for a maneuverable ICBM re-entry vehicle that was launched aboard Atlas F missiles. The BGRV used thrusters and (I think, judging by the appearance of its aft end) movable hinged rectangular drag flaps. Several test flights in the late 1960s demonstrated its ability to suddenly maneuver to "fall short" as well as to strike targets out of the plane of (to either side of, that is) its ballistic trajectory.

[2] The Alpha Draco test vehicle (see: http://en.wikipedia.org/wiki/Alpha_Draco and www.robsv.com/cape/c10ad.html ) was a two-stage suborbital boost-glide re-entry test vehicle that validated the technology in 1959. It would make a nice scale model as a complete vehicle (booster + re-entry vehicle). In addition, here are links to documents on early maneuverable re-entry vehicles, including the BGRV and Alpha Draco (see: http://books.google.com/books?id=lN...d=0CB0Q6AEwADgU and https://docs.google.com/viewer?a=v&...Rmru6CerRhjgDRA )

I hope this information will be helpful.
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Last edited by blackshire : 04-18-2012 at 07:46 AM. Reason: This ol' hoss done forgot somethin'.
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  #12  
Old 04-18-2012, 10:45 AM
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Thanks, blackshire!

I have always favored the PRIME and X-24B - but they flew like polished bricks. In the NASA book on the Lifting Bodies, one pilot even states that if one of the lifting bodies and a brick were dropped at the same time, the lifting body would touch ground first.

I did not know about the Alpha Drago - pretty slick. Could almost be a nose for a Nike Smoke ... hmmmm ...

My "SCALE" lifting body of choice is the FMX-4 "Facetmobile"

One of the things I wanna try with the X-24 is staging. TIR-24 shows an X-24 being launched on a Little Joe. If the booster is under 10" it can be simply gap-staged. This would allow me to two of my favorite rocket things (Stage and Glide) at the SAME TIME! My Rubicon might work for this.

1: I gotta get building
2: I'll post pics
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  #13  
Old 04-18-2012, 11:39 AM
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Quote:
Originally Posted by Ironnerd
Thanks, blackshire!

I have always favored the PRIME and X-24B - but they flew like polished bricks. In the NASA book on the Lifting Bodies, one pilot even states that if one of the lifting bodies and a brick were dropped at the same time, the lifting body would touch ground first.
Did you mean the X-24A? In a "Popular Science" article at the time, John Manke (if memory serves) said that the long-nosed X-24B--to his pleasant surprise--had positive lift after separation, while the X-24A, M2-F2/M2-F3, and HL-10 all dropped like bombs after release from the B-52's wing pylon (I'd also read that comment regarding the brick).
Quote:
Originally Posted by Ironnerd
I did not know about the Alpha Drago - pretty slick. Could almost be a nose for a Nike Smoke ... hmmmm ...
For an Alpha Draco scale model, the glide trim ballast could be placed in one of the four conical fairings, and the gliding second stage could be built so that the upper stage's motor (or motor mount, which could use streamer recovery) would eject itself to lighten the glider.
Quote:
Originally Posted by Ironnerd
My "SCALE" lifting body of choice is the FMX-4 "Facetmobile"
I remember that 'un...like Vincent Burnelli's flying wings, the Facetmobile is very crash-resistant. Its stall speed is also quite impressive--just 33 miles per hour! With its large exposed area, it would lend itself to solar cell-charged Li-Po electric battery power, which some full-scale motorgliders are already using (without the solar charging).
Quote:
Originally Posted by Ironnerd
One of the things I wanna try with the X-24 is staging. TIR-24 shows an X-24 being launched on a Little Joe. If the booster is under 10" it can be simply gap-staged. This would allow me to two of my favorite rocket things (Stage and Glide) at the SAME TIME! My Rubicon might work for this.

1: I gotta get building
2: I'll post pics
Yes--a BT-5 "stuffer tube" could help direct the burning propellant particles from the first stage motor up into the second stage motor's nozzle.
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Last edited by blackshire : 04-18-2012 at 11:45 AM. Reason: This ol' hoss done forgot somethin'.
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  #14  
Old 04-18-2012, 07:38 PM
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Quote:
Originally Posted by blackshire
Did you mean the X-24A?


Agreed. I forgot the X-24B fell slower than a brick


Quote:
Originally Posted by blackshire
For an Alpha Draco scale model, the glide trim ballast could be placed in one of the four conical fairings, and the gliding second stage could be built so that the upper stage's motor (or motor mount, which could use streamer recovery) would eject itself to lighten the glider.


This will require more study

Quote:
Originally Posted by blackshire
I remember that 'un...like Vincent Burnelli's flying wings, the Facetmobile is very crash-resistant. Its stall speed is also quite impressive--just 33 miles per hour! With its large exposed area, it would lend itself to solar cell-charged Li-Po electric battery power, which some full-scale motorgliders are already using (without the solar charging).


I was thinking the exact same thing - (great minds, etc...) the FMX-4 would be a great candidate for an electric plane (see also Sonex's Electric plane - very kewl)

Quote:
Originally Posted by blackshire
Yes--a BT-5 "stuffer tube" could help direct the burning propellant particles from the first stage motor up into the second stage motor's nozzle.


'Twould be a hoot! The stuffer tube would be required or the X-24 would just be blown off the booster. It would make for a very "Observer Friendly" flight.
But first I gotta get these little guys sussed out. I know the term "peak performance" is pretty relative in this instance, but I'm curious to see how much hang time I can get from a cone.
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  #15  
Old 04-18-2012, 10:10 PM
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Quote:
Originally Posted by gpoehlein
I used the Yankee nose cone (which is a pretty close approximation of the original) and 1/4" foam core for the fibre board bulkhead.
Greg,

I've used the Yankee cone as well. But it does weigh several more grams than the balsa cone. And that means a few more grams of weight aft to balance it out. The result is that you can end up with even more of a brick

Don @ Squirrel Works turned me on to this tidbit of knowledge. And I can't argue with it. That is, I have had more problems trying to trim my Yankee-coned bugs than the balsa ones. So, while it's only a few grams, this barely gliding glider needs all the lightening help you can give it.

Doug

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  #16  
Old 04-18-2012, 10:15 PM
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I seem to recall that the Centuri X-24 instructions suggested/recommended cutting the size of the fins down to improve boost performance. I did this as a kid after one of the fins tore on a cactus. I remember thinking the improvement was visibly noticeable both in boost and in glide.

Just a thought . . . .

EDIT: I just saw it in the tech report attached to another post.
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  #17  
Old 04-18-2012, 10:39 PM
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Quote:
Originally Posted by MarkB.
I seem to recall that the Centuri X-24 instructions suggested/recommended cutting the size of the fins down to improve boost performance. I remember doing this as a kid after one of the fins tore on a cactus. I remember thinking the improvement was visably noticable both in boost and in glide.

Just a thought . . . .



As I recall, the instructions said you could leave the Fins off, and build a booster for it, basically using it as a nose cone.
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  #18  
Old 04-19-2012, 05:40 AM
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I am using balsa nose cones from Semroc - they are inexpensive and add lightness.

I plan to build four (4) of these things and compair performance.

1: Basically Stock
2: Stubby Finned
3: Finless
4: Dunno yet.
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  #19  
Old 04-19-2012, 07:26 AM
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Quote:
Originally Posted by Ironnerd
I am using balsa nose cones from Semroc - they are inexpensive and add lightness.

I plan to build four (4) of these things and compair performance.

1: Basically Stock
2: Stubby Finned
3: Finless
4: Dunno yet.
Although I haven't tried it myself, the stubby-finned "Semi-Finless X-24 'Bug'" described and illustrated in TIR-24 "Model Rocket Lifting Bodies" (see: http://www.spacemodeling.org/jimz/tr/tir-24.pdf ) looks like it would perform well in both the powered ascent and gliding return portions of the flight. As the report says, "The addition of a little more rearward weight will coc.k the body's nose up to give longer, more gradual gliding returns." Also:

Eliminating most of the weight (as well as the drag) of the full-size fins by trimming them down for the semi-finless configuration would allow you to add that mass to the model's rear trim ballast instead, to coc.k the model's nose higher for better glide characteristics. (I apologize for having to mis-spell "coc.k" with an included period; the system's "dirty word detector" thinks I'm using that word in a vulgar manner--which I am not--and "blanks it out" with asterisks otherwise...*Sigh*) In addition:

A "triangular ring fin" (a ring fin whose perimeter follows the shape of the rear of the X-24's conical body) could be attached to the rear of the cone by three or more stubby (0.5" - 0.75" high) stand-off fins. If the chord of the ring fin is parallel to the model's direction of motion (if the chord *isn't* parallel to the cone's rearward sweep angle, in other words), its drag will be lower than that of a ring fin whose chord is parallel to the cone's rearward sweep angle.
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Last edited by blackshire : 04-19-2012 at 07:37 AM. Reason: This ol' hoss done forgot somethin'.
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  #20  
Old 04-19-2012, 08:02 AM
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Quote:
Originally Posted by blackshire
Although I haven't tried it myself, the stubby-finned "Semi-Finless X-24 'Bug'" described and illustrated in TIR-24 "Model Rocket Lifting Bodies" (see: http://www.spacemodeling.org/jimz/tr/tir-24.pdf ) looks like it would perform well in both the powered ascent and gliding return portions of the flight. As the report says, "The addition of a little more rearward weight will coc.k the body's nose up to give longer, more gradual gliding returns." ...



Does this mean that I will have to rework my X-24 patterns to include a stubby fin version?
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