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LPR w/ strap-on boosters!

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dtomko

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Wingarcher,
That's an intriguing plan. I would be concerned, however, about methods that use the ejection gasses from the sustainer to push out the boosters. There's going to be a lot of scorching on the boosters and maybe internal damage to the sustainer if there are only two holes to vent the gasses.
The more I think about rear ejection, the less I like it! Attaching the strap ons is much easier if you pop off the noses. That way there's less worry about the strap ons coming off under thrust because the rear attachment can be simpler and sturdier.
The most impressive system would have the strap ons fall off while the core is still boosting, but if you have a shorter delay in the strap ons and they fall off while the core is still climbing, that would also look nice.
DT
 

dtomko

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Jason,
Looking good! I'm wondering if you might want to make the lower hooks a little shorter to minimize the chance of the boosters snagging?
Drew
 

teflonrocketry1

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Here is my best attempt at a RockSim file for your design. I have not had the time to create the custom motor files for the flights so assume two C11's approximates a D12 core and Two D12's approximate an E9 core motor. I think the model is too heavy and wide for flights with just a C11 in the core.

Bruce S. Levison, NAR #69055
 

jetra2

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I knew it looked pretty sweet from when I first imagined it - now that picture confirms it! That is AWESOME! I still can't open the Rsim file, but I'm not surprised - it's a V7 file, I only have the demo. :(

Thanks Bruce!

Jason
 

teflonrocketry1

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Attached is a 2D picture showing the CP and Static Margin.

Bruce S. Levison, NAR #69055
 

teflonrocketry1

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Attached are some approximate data flights as described above.

Bruce S. Levison, NAR #69055
 

prowlerguy

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Here is a link that describes a different approach to seperating strap-ons. They used an R/C servo to seperate, then a wind-up timer to deploy the SRB chutes. Perhaps you could use a piston in the strapon to un-hook the booster and start the timer, then use the timer to deploy the chute/streamer via mechanical means.

https://members.aol.com/narshuttle/modeldetails.htm
 

Rocketmaniac

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Originally posted by prowlerguy
Here is a link that describes a different approach to seperating strap-ons. They used an R/C servo to seperate, then a wind-up timer to deploy the SRB chutes.https://members.aol.com/narshuttle/modeldetails.htm

Wow..... What a site!!!....... A lot of work went into that shuttle.....

Hey Sandman, can you make SRB "aft fairings" like in this pic?
 

havoc821

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I had an idea for strap ons that might be easier that I wil try one day on my Eye in the Sky 5. You would have a launch lug glued to the side of the strap on. On the rocket, you would have a small rod attached about an 1/8" or so from the side of the rocket body. The rod is bent at the top and glued. The thrust from the motor keeps the strap ons on and when the motor burns out on the strap ons, the boosters are coughts in the airstream and pulled off. Pic included.
 

slim_t

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Originally posted by havoc821
I had an idea for strap ons that might be easier....
Nice simple idea, but how would you keep the boosters on while on the pad?

Tim
 

MetMan

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This is the problem with fall away SRBs. While they look cooler, they are more problematic. The best way for this configuration is to use a "burn string" that either burns away upon engine ignition or at the end of a booster motor burn.

This way, the SRB stays in place if the motor doesn't light. That's the theory anyway. I'v got a photo of a 2.6" rocket with 3 SRBs lifting off, only one of the boosters is taking off solo! I'll post it this weekend if I get the chance...

MetMan
 

havoc821

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I could build some sort of special stand or somthing to keep the strap ons on the rod. If all else fails, I could just use stand offs that are equal length so both strap ons would be held the same distance up the rod that is on the side of the rocket. When the motors are lit (hoping they all light at the same time) they just stay in place because of the thrust. When the motors burn out, they just fall off. I don't see too much a problem with this. If I ever get a BT55 nosecone and at least 6" of BT55 tubing, I can start construction on the Eye in the Sky 5. I will attach a RockSim file, but it will not have strap ons because RS5 won't let you have outboards and I don't have enough money to get version 7. I don't even have enough money to get a BT55 nosecone or that 6"of BT55 tubing that I need. The only moey that I have ($16) will go toward paint for my 4inch horizon and a H165R to fly it on. After that, I will have no money untill grassc cutting season. :(
 

teflonrocketry1

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RockSim allows you to have outboards or strap-ons!

Take a look at the following Apogee Peak of Flight Newsletters:

https://www.apogeerockets.com/education/downloads/Newsletter108.pdf

https://www.apogeerockets.com/education/downloads/Newsletter109.pdf

https://www.apogeerockets.com/education/downloads/Newsletter110.pdf

https://www.apogeerockets.com/education/downloads/Newsletter111.pdf

I can help you with these simulations, since I helped Tim Van Milligan write these articles. Using my side pod simulation article these strap-on booster simulations are even more accurate:

https://www.apogeerockets.com/education/downloads/Newsletter119.pdf

Strap on boosters in a parallel staged configuration require one to build unique motor files for each flight which is not trivial.

Bruce S. Levison, NAR #69055
 

slim_t

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Originally posted by havoc821
I could build some sort of special stand or somthing to keep the strap ons on the rod......
oh, ok, yeah that could work.
I just love simplicity, only sometimes the simple solution is not so obvious. Might have to try that myself sometime.
The boosters may still need some lower support to keep them moving around like a loose tooth, but it could be on the sides and still not interfere with the booster falling away.

Tim
 

dtomko

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This was the system with the Titan IIIM; the strap ons would stay attached from the thrust of their motors. In order for this to work the strap on motors need to be higher thrust than the core motor or motors. This is tough without something like the B-14 available. So you're safer going with a system that locks the strap ons to the core until burn out
DT
 

havoc821

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"I will attach a RockSim file, but it will not have strap ons because RS5 won't let you have outboards and I don't have enough money to get version 7."

Notice how I said I have Rock Sim 5 not 7. You can only do strap ons in 7. It's ok, I tend to look over things too sometimes. :)

dtomko,

I never thought about that. I might but a B6 as a core and 4 C6s as the outboards. Well, I gotta go eat dinner now.
 

teflonrocketry1

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You can simulate parallel staging with strap-on boosters using RockSim Version 5.0.2. The article I originally submitted was too complex and convoluted to publish in the Apogee newsletter. It also used a different technique to simulate side pods that had less basis for accuracy than my recent side pod simulation article. Tim Vam Milligan rewrote the entire article for at later version of the software.

See the attached zip file for the first part of the article.

Bruce S. Levison, NAR #69055
 

teflonrocketry1

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Here is part two of my originial parallel staging article.

Bruce S. Levison, NAR #69055
 

teflonrocketry1

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Here is part 3 of the article; sorry I had to cut up the document and compress it into zip files but this was the only way to post it here!

Bruce S. Levison, NAR #69055
 

teflonrocketry1

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Here is part 3 of the article; sorry I had to cut up the document and compress it into zip files but this was the only way to post it here!

I remembered the attachment this time!

Bruce S. Levison, NAR #69055
 

MetMan

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Originally posted by slim_t
Nice simple idea, but how would you keep the boosters on while on the pad?
It's important to have positive attachment of all the boosters until they are able to stay attached by their thrust.

Here's what happens when they don't. This is a 2.6" rocket that has 3 parallel boosters (Alphas with one fin). I used strings taped to the sustainer run through the nozzles to secure the boosters. I think one of the boosters wasn't fastened securely enough and then lit...
 

havoc821

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COOL! Well................maybe not for you. Good picture though. Once I get all the parts, I will play around with the strap ons and test different designs. Thanks for the tips!
 

nomopbo

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I just got to tell you that that beast absolutely ROCKS! I had an idea to put motors on the "Screamin Mimi" rather that those goofy whistles...but that thing is SWEET! You guys should be proud.
 

Justin

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Jason-
Very cool pics. I'm from St Pete, so I hope to see that thing fly when I get back there If there is a TRF launch in the Tampa St Pete area.

I built a bt60 rocket that sounds much like what you're doing ('cept the boosters don't come off). I havn't flown it yet, single or clustered, because of progress eating my field here.

I think I posted this pic befor. Here it is primed anyway.
 

havoc821

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I have a Screamin Mimi, but I don't know what to do with it. I am using the 4 "whistle" tubes and some 4 extra conical nosecones that came with the designer's special kit for the strap ons on my Eye in the Sky 5, but I don't know what to do with the rocket itself. I was going to make a clone Maxi Citation Patriot, but I changed my mind. Any suggestions?
 

eugenefl

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Originally posted by Justin
Jason-
Very cool pics. I'm from St Pete, so I hope to see that thing fly when I get back there If there is a TRF launch in the Tampa St Pete area.

I built a bt60 rocket that sounds much like what you're doing ('cept the boosters don't come off). I havn't flown it yet, single or clustered, because of progress eating my field here.

I think I posted this pic befor. Here it is primed anyway.
Justin, we meet on the third Saturday of every month. Drop me or Jason a line and we'll get you directions and further info. We're tiptoeing on finalizing our club.

Cool looking booster rocket!
 

Justin

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Eugene & Jason-
I'll be in town on wednesday or thursday, I'll e mail when I get settled. Turns out I'll be in tampa , not St Pete, but still close to your club I think..

Got stuff Ive been waiting to fly!
 

JStarStar

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Originally posted by dtomko
Looks excellent! I have plans from the Aug. 1970 Model Rocketeer for a conversion of the Estes Gemini Titan to a Titan III MOL with working strap ons. The strap ons used B-14-0s and the core used 2 B4-4s or C6-5s. The strap ons were held on only by clips in the rear and pins at the front, both made of 1/32" music wire. So there is a loose connection and the strap ons fall off with just a tap. The method was to use the more powerful kick off of the B-14s to keep the strap ons attached; after burn out, they would fall off as the core keeps boosting. The article mentions that the B-14-0s will pop out the nose cones of the strap ons, but recommends the cones have very loose fits. And the strap ons are 18" BT-70s with no stuffer tubes! It's on my list to build, but obviously some different engine arrangement needs to be worked out.
Drew Tomko
I remember building a parallel-staged rocket on this very concept. The strap-ons were attached by a vertical clip system which would only stay on as long as the strapons were accelerating faster than the core (which would be the case with B14's). At burnout of the strap-ons, the core would continue to accelerate while the strap-ons were kicked off by air drag and the kick of the booster engine burn-throughs out an 'ejection vent' hole you had to drill in the nose cone.

I actually built this and flew it OK a couple times. The eventual idea was 3 strap-on boosters and a 3-stage core. I never did figure out what was going to happen if the core ignited a split second before the strap-ons - I guess the answer to that would be, "Duck." :eek: :eek:

Those B14-0's did have some uses. I wish Quest would start making them.
 

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