SCRATCH BUILD done -fall off boosters rocket-

[[POW]Eagle159]

I got my Scratch build rocket done a bit ago and want to see what you guys think....
It is a bt-80 core tube with bt-60 strap on boosters.
3 engine cluster, 24mm mounts, 2 C11-3s and a D12-5 in the core.
45'' tall, and weighs 10.5 ounces fully loaded. the boosters are only .33 oz ea. empty.
The boosters have 10'' chutes and the main has a 15'' chute.(all custom made).
The boosters get to around 150' before falling off and the core gets to around 500-600' or so.

I tried a NASA-ish type paint scheme with the orange and white.
She has so far flew once and worked perfect.

Yes, the boosters actually fall off in flight, just like the Space Shuttle.
It uses a simple ''dowel and tube'' connection system, the boosters slid into place in the main tube and while under power they are pushing up on the core rocket, when the .9 sec. thrust of the C11 stops the core is still accelerating with its D12 so the boosters slide off by drag, gravity and acceleration.

Any questions/comments are very welcomed!:horse:

 

[chadrog]

Looks good! Make sure you get video!!

 

[Scotty Dog]

Nice job.
Im not sure,but I think to launch it at a some club launchs,you would have to have a burn thru string set up.
Has something to do with making sure the main doesnt leave before the boosters if the boosters fire late. If they did ,you would have boosters flying every which way.
Im sure someone else can tell you (and me) more about this.

Putiing that aside, again,very nice job.
Whats the stripe at the color change on the main?
Is it Auto pin stripe tape?

 

[[POW]Eagle159]

Nice job.
Im not sure,but I think to launch it at a some club launchs,you would have to have a burn thru string set up.
Has something to do with making sure the main doesnt leave before the boosters if the boosters fire late. If they did ,you would have boosters flying every which way.
Im sure someone else can tell you (and me) more about this.

Putiing that aside, again,very nice job.
Whats the stripe at the color change on the main?
Is it Auto pin stripe tape?

Yes, thanks for that information, but I don't see my self going to a club any time soon....
And Yes, it is pin striping, it is a metallic red.

I have added more pin striping to the main and boosters, I just need to take a picture of it now.:horse:

 

[JStarStar]

Long, long ago (40 years or so) I built a parallel-stage rocket that worked on the same principle: the outboards were B14-0s (then available) and the core was a 3-stage C6-0/C6-0/C6-7.

The mounting pods were built in such a way the outboards would drop off from air drag when the thrust of the B14-0's fell below the still-burning sustainer phase of the C6-0 in the core. I used mounting pins fairly similar to what you've done here.

For CG purposes the outboards were actually mounted on the second stage (putting them on the first stage loaded up too much weight in the rear).

It worked correctly a couple times, but never flew STRAIGHT -- almost always it would veer off at a fairly sharp angle when the outboards dropped.

We didn't have video clips of launches in those days so all we could go by was what we saw with our own eyes and had to reconstruct/guess what had happened.

The outboards never dropped in a nice orderly pair (as we have seen with the shuttle, etc) but would tumble off at random angles.

We guessed what happened was that one outboard burned out and dropped a fraction of a second before the other one, which sent the whole stack off at an angle for whatever time Outboard B was still thrusting. Even if it was only for 0.01 of a second, that might be enough to knock the rocket off vertical and send it off at an angle.

We did have one "major launch anomaly" where the whole kaboodle came apart as it left the rod.

It wasn't too hard to figure that one out: the core motor lit a fraction of a second before the outboards, so it started up the rod -- and out of the mounting pods -- sooner, and by the time the outboards lit you had three different vehicles going in three different directions.

We had anticipated that might happen and had taken care that all the igniters were properly installed, the clip-whips were relatively short and kept clear from shorting, plus we were using a full-voltage car battery to launch, so there was no apparent reason (i.e. weak battery) why one igniter would have heated up faster than the others.

At the time we thought everything involved with rocket motors was a precision kind of thing, we didn't figure it was entirely possible you could have everything hooked up perfectly and have one motor ignite 0.02 seconds before the others -- enough to start it up the launch rods and jiggle the mounting pins loose before the other two lit.

:y::y:

So the moral of this whole story is, I think you have to have some kind of active-jettison/retention process like a burn-string set up to prevent the whole bundle coming apart in an order you hadn't really planned.

:shock::shock:

Not to say your model can't work as you say it has -- as I said, the one I built back in 1971 or so did work a couple times -- but when it didn't work, I had three separate rockets flying in three separate directions.

 

[Woody's Workshop]

Eagle, I like the way you did the boosters. I've fiddled with a similar design for some time, but have been stuck on the booster drop off.
I actually thought about a butterfly that used the ejection charge to push the booster off and away, but this by far much simpilar.
I will just need to adjust booster fin placement so they stay attached at the pad.
Thank you for sharing, very very helpful info!

 

[peter_stanley]

That's awesome looking build! If you have any problems with the drop-off boosters you could try adding another set of dowels/lugs, one set for each section of the booster, but attaching from opposing ends. Although not perfect it would provide some positive retention in the event one or both of the boosters were delayed slightly longer than the main.

I used this method on a rocket I built with good success. Here's my Rocketreviews article showing more detail, https://www.rocketreviews.com/scratch-pcr-by-peter-stanley.html. I got the idea from another Rocketreviews submission, describing the same technique on the project Omega rocket.

 

[Highpowerrocketyahoo]

The rocket looks awesome! I like the paint scheme. The dowel setup looks very well done!
If anyone has any pics or more info on this burn string setup I'd be interested in that.

 

[[POW]Eagle159]

That's awesome looking build! If you have any problems with the drop-off boosters you could try adding another set of dowels/lugs, one set for each section of the booster, but attaching from opposing ends. Although not perfect it would provide some positive retention in the event one or both of the boosters were delayed slightly longer than the main.

I used this method on a rocket I built with good success. Here's my Rocketreviews article showing more detail, https://www.rocketreviews.com/scratch-pcr-by-peter-stanley.html. I got the idea from another Rocketreviews submission, describing the same technique on the project Omega rocket.

WOW, Thank you for that info! Very nice to read.




THANK YOU for the comments everybody!
I really enjoy to read the comments, now I want to build more!

 

[[POW]Eagle159]

I got some more pictures now, The finished rocket!
The first is the rocket now named The S.S.L.E. Eagle (Small Scale Launch Experiment) on the pad, an estes E-pad with a 1/4 inch 4' rod.

The bottom view, the boosters sit on used engines and the core sits in between the two boosters. (I will look into the burning string method. I know a little about it and will do more research.)
A picture of the pin-striping and the booster connection.
The two boosters sit together.
The core rocket sits with out boosters. (It can fly with out boosters, but wheres the fun in that?)

 

[[POW]Eagle159]

I took a simulated launch sequence....

1. Launch with all 3 engines burning together.
2. Boosters fall off with engine burn out. Core still under thrust speeds up.
3. Core starts coasting, Boosters eject chutes.
4. Core poops chute and all 3 parts fall safely, the boosters touch down than like 5-10 sec, latter core touches down.


Any questions?!?

 

[[POW]Eagle159]

Some close ups of the attachment system.

I just drew a center line first, then I choose a 1cm off set to either side, off of that mark, I then drew a new line to set the 1 inch long dowels on and glue on straight.
There are 4 dowels and straws per side, 2 top 2 bottom.
The booster side of things had the same thing done, 1 cm off of center and glued on a 1 inch long straw on each line. Before the glue fully dried I test fitted the booster on the core to make sure it all slides well.
What ended up happening is that 1 booster can fit either side, but the other booster can only fit on 1 side, because it doesn't slide well on the other.


So there we have it, The S.S.L.E. Eagle.:wink:

 

[modeltrains]

I used this method on a rocket I built with good success. Here's my Rocketreviews article showing more detail, https://www.rocketreviews.com/scratch-pcr-by-peter-stanley.html. I got the idea from another Rocketreviews submission, describing the same technique on the project Omega rocket.

I'm lost, cant figure out how that works with the pins going opposite directions --> https://archive.rocketreviews.com/images_descon/boosteratch.jpg (please have pity on my brain - the poor thing is on pills for muscle spasms)

 

[peter_stanley]

I'm lost, cant figure out how that works with the pins going opposite directions --> https://archive.rocketreviews.com/images_descon/boosteratch.jpg (please have pity on my brain - the poor thing is on pills for muscle spasms)

The pins are actually pointing inward toward each other. When the two halves of the boosters are fitted together, the top part has dowels that slide down into the top set of attachment lugs. The bottom section has dowels that slide up into the lower set of lugs. This way if you were to pick up the rocket (or the main lights before the boosters), the boosters will still stay on. But during boost they are pushing up against the main. Please let me know if this doesn't make any sense. Sometimes my explanations are not too clear.

 

[Serpico]

When will we be seeing this rocket launch?? I can't wait to see video of this baby!

 

[[POW]Eagle159]

When will we be seeing this rocket launch?? I can't wait to see video of this baby!

Im going to get and on-board video at the next launch.... Hopefully soon, but really it will be a few months before I go out again. :cry:

 

[jadebox]

Im not sure,but I think to launch it at a some club launchs,you would have to have a burn thru string set up.
Has something to do with making sure the main doesnt leave before the boosters if the boosters fire late. If they did ,you would have boosters flying every which way.

Carl Campbell's Delta IV Heavy (which is available as a kit from DFR Tech) uses that technique. I've seen him fly the rocket many times. The rare times when something went wrong, it wasn't all that dramatic.

If one of the outboard boosters doesn't light, the rest of the rocket makes a slow graceful arcing flight ejecting the 'chute just above the ground.

If the main stage ignites by itself, it makes a normal flight.

If all three motors light, but at slightly different times, the three pieces fly off on their own. The outer boosters stick with the main section long enough to fly upwards. And, amazingly, the two-finned outer boosters fly pretty well on their own.

-- Roger

 

[adrian]

I'm lost, cant figure out how that works with the pins going opposite directions --> https://archive.rocketreviews.com/images_descon/boosteratch.jpg

If you look closely, you can see that the booster body tube is cut around. It's designed to blow apart. When the booster blows its nose off, the forward dowel no longer holds the booster to the sustainer, so the booster can drop off.

A B6-0 or C6-0 has no official ejection charge but when the propellant burns through, it produces enough forward pressure to blow the nose off a small booster like that. Or, for that matter, a larger booster. I also have a couple of parallel staged rockets which rely on this fact to separate their boosters, one of which is my Thunderbird SAM.