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  #11  
Old 08-21-2008, 01:41 PM
snaquin snaquin is offline
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Quote:
Originally Posted by Green Dragon
2) there is a concept called a ''rack rocket' wherein motors just kick back out of a slotted / vented tube - I have flown 5 stage D12's in an Achilles rack rocket design ( see the Oct or Dec 1985 Tripolitan for plans )
Much fun, need to build another one

~ AL


AL

I had posted a link to an interesting article for another forum member a while back that was written by Ken Good called "The Rack Rocket Concept - The Quest For High Altitude".

The link is contained in this post

http://forums.rocketshoppe.com/show...69&postcount=22

A three stage rack rocket would be a fairly simple build.

.
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  #12  
Old 08-21-2008, 02:15 PM
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STRMan STRMan is offline
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All this talking about 3 stagers got me pining after a Centuri T-Bird. What a cool rocket to clone, I thought. Due to the weight of this model, and it's engines, the ONLY recommended engine to use in the first booster is a B-14. We know we won't see any of them any time soon. I wonder how long the rod would have to be to boost this on a B6-0 or C6-0 to get it up to a stable speed.


Last edited by STRMan : 08-21-2008 at 02:16 PM. Reason: sp
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  #13  
Old 08-21-2008, 02:46 PM
Ltvscout Ltvscout is offline
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Quote:
Originally Posted by STRMan
All this talking about 3 stagers got me pining after a Centuri T-Bird. What a cool rocket to clone, I thought.

Let's keep our fingers crossed that Carl can find a source for CPT-10. Then we can have Semroc kits of the long awaited Payloader II and the T-Bird!
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  #14  
Old 08-21-2008, 03:42 PM
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Shreadvector Shreadvector is offline
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Use a C11-0 or D12-0 in the booster, but verify the stability. I suspect the C11-0 will be OK.



Quote:
Originally Posted by STRMan
All this talking about 3 stagers got me pining after a Centuri T-Bird. What a cool rocket to clone, I thought. Due to the weight of this model, and it's engines, the ONLY recommended engine to use in the first booster is a B-14. We know we won't see any of them any time soon. I wonder how long the rod would have to be to boost this on a B6-0 or C6-0 to get it up to a stable speed.

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  #15  
Old 08-21-2008, 05:53 PM
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STRMan STRMan is offline
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Quote:
Originally Posted by Shreadvector
Use a C11-0 or D12-0 in the booster, but verify the stability. I suspect the C11-0 will be OK.


I can live with that. Just modify the lowest booster for a 24 mm mount. I'm completely embarrassed that slid by me. I was thinking this was a minimum diameter rocket, but I can see it is not right in the catalog. Thanks.
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  #16  
Old 08-21-2008, 06:00 PM
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Doug Sams Doug Sams is offline
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Quote:
Originally Posted by STRMan
All this talking about 3 stagers got me pining after a Centuri T-Bird. What a cool rocket to clone, I thought. Due to the weight of this model, and it's engines, the ONLY recommended engine to use in the first booster is a B-14. We know we won't see any of them any time soon. I wonder how long the rod would have to be to boost this on a B6-0 or C6-0 to get it up to a stable speed.[/IMG]
Fred's right - rig it to take a 24mm motor in the 1st stage (ala the Comanche).

I'd make a bunch of other changes in the passport stuff, too. It need not be that complicated or heavy. And I'm skeptical of its reliability as well. Why have vents if they don't open until after the stages begin to separate?

Doug

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  #17  
Old 08-21-2008, 06:26 PM
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Quote:
Originally Posted by Doug Sams
Fred's right - rig it to take a 24mm motor in the 1st stage (ala the Comanche).

I'd make a bunch of other changes in the passport stuff, too. It need not be that complicated or heavy. And I'm skeptical of its reliability as well. Why have vents if they don't open until after the stages begin to separate?

Doug

.


The passport staging always works perfectly on my Centuri Stiletto. I think the concept is that as the booster starts to separate from the sustainer, the hole become exposed, releasing some pressure. This slows down the separation of the booster long enough for the sustainer to ignite. In the passport staging setup, the engines are in direct contact with each other, so there is no place to have a vent anyway.

When I made an upscale of the Stiletto, I used traditional vent holes, as the engines were now gap staged about an inch apart.
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  #18  
Old 08-21-2008, 07:53 PM
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Doug Sams Doug Sams is offline
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Quote:
Originally Posted by STRMan
The passport staging always works perfectly on my Centuri Stiletto. I think the concept is that as the booster starts to separate from the sustainer, the hole become exposed, releasing some pressure. This slows down the separation of the booster long enough for the sustainer to ignite. In the passport staging setup, the engines are in direct contact with each other, so there is no place to have a vent anyway.
Looking at the plans for the T-Bird, there's a 1/4" gap between the 1st and 2nd stage motors. It does appear the 2nd stage motor abuts the sustainer.

I agree the vent opening will relieve the pressure and thus help slow the separation - or at least prevent it from gaining any more speed - but it still strikes me as klunky and suspect. That said, I haven't tried it, so I gues I shouldn't knock it

Doug

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  #19  
Old 08-21-2008, 08:15 PM
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Mark II Mark II is offline
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Quote:
Originally Posted by STRMan
"Those who fail to learn from history are doomed to repeat it" Sir Winston Churchill

Please elaborate my friend. Inquiring minds (well, at least one ) want to know.

Well, OK. I never actually saw anyone use this method, and I don't recall what it was called. I learned about it when it was discussed in a thread on the Oldrockets Yahoo! group a couple of years ago. This method of staging involved joining booster motors and a sustainer motor end to end in the same manner as in direct staging, but bonding them together with epoxy instead of joining them with tape. The permanently joined motors would all fit into one long motor tube, with the nozzle of the rearmost booster motor (1st stage motor) being positioned in the usual place at the aft end of the rocket (and not hanging off the back, as in CHAD staging), with the rest of the motor stack extending well up into the rocket. With the motors permanently attached to each other, none of them would drop off as they burned out. Instead, the next motor would fire right through the (supposedly) empty motor casing(s) of the previously burned motor(s).

Just thinking about this for a second, you can well imagine how anyone using this method is really begging to get a CATO. Sure, MOST of the BP propellant is gone once the motor is burned, and there is a wide open passage for the next motor's exhaust to blow through. But there is still a fair amount of burnt residue left in the spent motor's case, and apparently it is all too easy for the next motor's exhaust to dislodge a chunk of that residue and send it down to the nozzle where it will sometimes block the exit port. Blocked nozzle exit port = CATO, every time. And a burning stack of permanently joined BP motors that experiences a blockage in its nozzle's exit port becomes the equivalent of a pipe bomb.

Regarding rack staging: I have heard the term, but I have never gotten a handle on how it works. Is there a diagram somewhere of the setup that also illustrates the whole staging process?

Mark \\.
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  #20  
Old 08-21-2008, 08:42 PM
shockwaveriderz shockwaveriderz is offline
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Quote:
Originally Posted by snaquin
AL

I had posted a link to an interesting article for another forum member a while back that was written by Ken Good called "The Rack Rocket Concept - The Quest For High Altitude".

The link is contained in this post

http://forums.rocketshoppe.com/show...69&postcount=22

A three stage rack rocket would be a fairly simple build.

.


I agree with you Steve. Rack staging is much more effcient than nomal staging.... but a method needs to eb developed that allows the engine casings to fall with an attached deployed streamer for safety.

terry dean
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