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WiK

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I just had a brainwave! :eek:

You know the Estes Operation Enduring Freedom Paveway... Well wouldnt it be cool to launch it, then have the EC blow off the stabilising fins so the normal fins stay, and have it free fall like a bomb to say 300ft, then have a small altimiter blow out a chute? (See the attatched badly drawn image for more info).


Would this be possible? Would you be able to have the stabilising fins sturdy enough to stay on and keep straight in flight and then be blown out by an ejection charge? Would there be a deploying altimeter small enough to fit in it? Would there be a strong enough chut to withstand that? Would this add too much weight? Is this too many questions? :p

Feel free to comment...


Phil
 

powderburner

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I am not sure which fins (or parts of fins) you have identified as 'stabilizing' versus 'normal' because the fins on the Estes model pretty well represent the actual hardware.

The real GBU weapons have folded aft fins because they must 'fit' onto a carrier aircraft. At weapon release, the GBU falls free of the aircraft for several feet before a lanyard triggers the opening of the aft fins. Those fins unfold and remain in that configuration until business is concluded.

There are two difficulties I can see with your plan to 'free-fall' the model rocket toward the ground: First, the 'chute opening will be a pretty severe condition, potentially leading to stripped parachutes, ripped shock cords or tethers, and zippered BTs. Second, accuracy of the timing of the main recovery system will become fairly critical to successful (safe) operation, because a small fraction of a second delay will earn you an immediate invitation to leave the range.

Interesting idea, but perhaps a bit dicey?
 

sandman

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The problem is...the Paveway is NOT a rocket...but a bomb!

This model just has a rocket motor in it for...well, 'cause Estes made it a rocket...or something...or a model of a...oh, nevermind!

sandman
 

PWALPOCO

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OKeis , Im the Newbie , so heres a newbie point.

WiK wants the rocket to land in a kind of nose first like a bomb.

Perhaps your idea would work on an bigger version of paveway where you could put in some concealed pods for a rear eject chute system , allowing the "bomb" to come down nose first ? Then the bomb could come down pretty well in the form it went up in .... just with trailing chutes ?

Ho hum ....

Paul
 

jflis

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actually, that is what I was thinking too

SEE??? All you other newbies out there?? CONTRIBUTE! :)

Building a rear ejection model would solve the parachute deployment problem (I *do* still agree that there is a concern with accuracy on the altimeter/timing, if you could even find one small enough...)

To do rear deployment you simply glue on the nose cone and *don't* glue in the motor mount (you would have to have some sort of a "motor mount block" that serves the same purpose as the engine block, though)

Upon ejection, the engine mount (with engine) kicks out the rear, pulling the parachute with it (no zippers :) )

jim
 

Zippy

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PWALPOCO and jflis's ideas for rear ejection are great. I would only add that you should use as small a parachute as you can get away with so it comes in relativly fast. Maybe a little beefing up of the rocket wouldn't hurt either. :D
 

WiK

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Well I just realised I forgot to attatch the picture... It is VERY badly drawn :)

When I say the Stabilising fins, I meant the ones that stick right out. I just searched "paveway bomb" on google images, and saw that they are on the original one aswell. Soo I wouldnt have to have the fins blow off. The rear ejection sounds good. The only thing now would be making sure it is stable when it free-falls, its stable and doesnt tumble.

What BT size is the main tube?

Paul, the idea is for it to free fall like the real bomb for a bit then deploy

gotta go
 

Zippy

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So you want it (judging by the diagram) to freefall nose down one hell of a long way before the chute deploys? I don't know if the flight profile your looking for is truly doable but I'd try a looooong ejection time and a relativly heavy nose weighted model built to take abuse.
EDIT: Oh yea, it will probably shred a stock chute so consider upgrading that. :)
 

WiK

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LOL! :D

I cant quite imagine an Estes plastic chute taking all that stress. I would certianly use a small chute that was designed to be used as a drouge in M/HPR rockets.

And talking about chutes, I remember seeing a video of a Brit launching a Thunderbird 3 on 3 D motors. The delays were wwaaayyy too long and the chute ejected at about 10 feet. It was an estes chute and it slowed it down enough for a safe landing. Maybe that was a fluke.

Pauls rear ejection would be more practical, but looses the whole idea I was going for (which is to have it drop on its own like the real bomb does, and then eject at the last moment).

Would I be able to use C6-0 booster motors in the rocket, and have an altimiter do a rear ejection? Because I dont think a 7 second delay would be long enough for it to fall properly.

Would a PerfectFlite MAWD fit in there?

Cheers,

Phil
 

powderburner

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We need someone to chime in here and inform us about the accuracy and consistency of the output signals from rocketry timers. If you want to scare the crowd with a dive-bomber attack, and then punch out a 'chute at the last moment, the timer will obviously be the critical link in this setup.

I suppose you could run some sims first, to get in the ball-park on the correct settings for the timer (timers? maybe redundancy would be called for here, for safety). Then you could get some empirical data by starting off with short times to eject relatively higher, until you see how well it works. Then you could start extending the time settings to let it come lower, a bit at a time.

Probably the biggest single problem you will run into is motor consistency. There is some level of variation in total impulse that is accepted at the factory, and it is a significant variation. How will you know which motor you are using (a 'hot' one, versus a 'dud' load?) for any given flight? This will determine how high you get, and how long it takes to descend, and will mess up your timing to eject at the last moment----I'm guessing this motor performance variability would be the real problem.
 

Zippy

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I think the PerfectFlite MAWD will fit into a BT-50, but I can't see putting a $100 altimeter in a $12 rocket. I'd love to see it happen though as long as some one else is doing it.
 

DavRedf

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Hi Wik
just measured the BT on my paveway 1.285" no idea what BT that is but it is plenty big enough for an altimeter or any other payload.
David
 

PWALPOCO

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Well the reason I was thinking of having it come nose down on the chute was because I recall Woodys Fireflash coming down on only a partially opened chute and with BT absent.

The nose in the fireflash is quite weighty , and as it came down on just that , the BT seperated .... it fell more or less like a rear ejected chute nose first. There wasnt any spiralling or drift , it fell pretty fast and straight. Mimicking that would mean no complicated timers etc but wouldnt be the same as the profile you wanted.

Another easy way might be (Im a unqualified noob , dont trust me !) .... artificially make the paveway heavier and place a long delay on it. It wont climb so high and will be falling longer so the thing would be closer to earth before deploying the chute. So a "heavy" paveway on a Cx-y with a big delay might help ?

Only thing after that may be the timer/altimiter/jedi mind trick option ......

Paul
 

WiK

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Well I was thinking of getting a MAWD anyway. I want a loggin altimiter with the functions of the MAWD, and I was gonna get the version of the MAWD without the deployment, but someone pointed out if I spent the extra money now, I wouldnt have to buy *another* altimiter when I needed deployment.

Then again a timer sounds a better option. Theyre not too expensieve are they?


Anyone got a ROCKSIM V 5 compattible sim of the paveway? Im no rocksim wizard :)

Thats some interesting points about the motor burn times Powder.


Thanks for the input everyone! :D
 

edwardw

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Why not do this to determine timing. Go and buy two rocket. Use one with the engine you want to fly it, but make it a 0 delay that way you just go up and then come right back down and core sample with your test rocket. Then if you have a video camera capture the sequence then determine the delay you want. I think that this is nicer than a $100 altimeter. And once you know the time, maybe you can even set up a timer....Just a thought though.

Edward
 

slim_t

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I think I'd just go with the rear ejection and use a C6-7 or B6-6. You could add weight to get the desired effect. Of course it would take alot of simming or trial and error to get it right, and you wouldn't want to test in the presence of a crowd, but I don't think you really want to risk slamming into the ground by deploying 20 ft above the ground, do you? I think you could get what you want and still deploy 100 ft up. A 6 or 7 second delay can be plenty of time to turn and come down a good bit before ejection if the rocket's weighted right. Actually those B6-6's can be a bit scary even in a light rocket.
Just my 2 cents.

You know, this might even be more fun with the Cluster Bomb, blowing out those little bombs at about 100 ft up, like the real thing.

Heads Up!!! :p

Tim
 

stevem

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jflis- perhaps Fliskits could come up with a kit that uses rear ejection as you described.

I for one am always looking for kits that are out of the ordinary.
 

rokitflite

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OK, how about this... Scrap the recovery system all together, glue the nose cone on. Using some huge pieces of foam rubber make a quarter scale model of an Iraqi chemical weapons plant. Use this as a spot landing target. When the rocket hits it it will bounce off! You can bomb it again and again for a truly scale flight! OR if you are worried where the rocket will go after it bounces off, make the plant out of a huge Jello mold so the bomb will stick in it! (wild cherry flavor might work best)...

Actually, never mind. This is a bad idea.
 

WiK

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LMAO!!!! :D:D:D Thats an "interesting" idea! And if ya miss with the Paveway, get out the Cluster Bomb on a 7 sec delay and drop a load of bomblets on it :)
 

Missileman

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OK here's an idea, maybe stupid but and idea none the less.
Rear eject the motor with mounts on a separate chute but have this ejection pull out a clear streamer of enough size for safe recovery.
This will give you a nose down attitude and the clear streamer will look like a vapor trail.
Just a thought.;)
 

PWALPOCO

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Yeah I like that ,

I guess you could get away with just rear ejecting streamers ? That way it could get to apogee then do a rear ejected streamer recovery.....

Onto the foam "Baby Milk Factory" but thats another story ......

Paul
 

WiK

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That sounds like a very good idea Missileman :) I might try that to start off with!
 

Missileman

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I can expand on how to do this also as I have a rear ejected model.
Build your motor mount as normal but do not glue into body tube.
You will need a thrust ring inside your body tube where your fwd cr will sit.(this can be a short piece of coupler)
You will need a length of kevlar cord (doesn't have to be real long as you will be separating MM and main body at ejection)
Tie a knot in cord and place under thrust ring when you glue it in (this gives you a secure ancor point)
Tie streamer to other end of cord.
Tie another cord to center area of motor mount between CRs (this cord attaches to a small chute to recover motor assembly, bright chute recommended)
Make a small slot in edge of fwd cr for streamer cord to pass through and beef up fwd ring.
Pack motor chute in zigzag pattern and place next to motor tube between CRs. Do the same with streamer on opposite side of motor tube.
Slide tube into rocket, load and launch.:D
Packing your laundry this way does 2 things
1 ensures proper deployment
2 protects chute and streamer from ejection charge (no wadding needed)
Make sure you glue nosecone on!!!

Hope this helps
Have fun
Jim
 

Neil

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Well, if you decide to go with a chute, use a ripstop nylon one. Estes stuff shreds like THAT. I was pulling on the shroud lines of one of my chutes as hard as I could, and then I went into my room... I noticed an Estes chute sittin in a box... I pulled on a shroud... POP. Another one. POP. Another and another and another....:eek: pop pop pop. So THAT is why my estes chutes never lasted 2 flights....:eek: Im positive one of my (or anyone elses, as long as they have the shroud lines sewn on really well) could take a deployment like that. :cool: :D Any nylon chute can take it, but I will reccomend my own because I am the one writing this!;) :p

This is a very... We... shall we say "interesting" idea....:eek: ;) :p
 
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