multi-engine stage

[user 1400]

I'm new so don't hurt me if this sounds stupid. Does anyone know of a kit or homebuilt that successfully stages more than one estes type engine reliably? I mean using the standerd tape junction method. I think I may have figured out how to get past the timing issue which is the only major problem I know of. It should be an interesting flight if it works!


Peace,

Mike

 

[powderburner]

I am not quite sure that I understood your question.
Did you mean a rocket design with multiple motors in the booster, and also multiple motors in the upper stage?
Or, if that wasn't it, can you explain a bit more about what you did mean?

 

[user 1400]

multiple engine first stage and multiple engine second stage directly linked engine to engine. Just as you said.

Peace,

Mike

 

[Micromeister]

Mtmind:
Nope! what you are asking to do, Will Not Work!! Please do not attempt this method.
The easiest way to explain this near absolute, is the 10% varience in the manufacture of the motors, both in motor impulse and time delays. If you have ever launched a clustered black powder model, I'm sure you have noticed the Pop,Pop, Pop ect... as the ejection charges have ignited or Booster motors have burned thru. This is due in large part to the slightly different burn rate of each motor, even within the same batch the BP or APCP there will be enough difference in the burn to make direct multi motor staging nearly impossible (I only say "nearly" because I personally don't believe anything is impossible). That said the "Nearly" is so remote as to not be a factor. These manufactured variences and the fact all the motors will not ignite at precisely the same moment, make for a very unpleasant second staging event. At best one or possibly two motors in your cluster will light before the sustainer has pulled away for the first stage, pulling other motors from the upper stage to light slightly later outside the model or falling free, the now off set thrust in the upper stage will send it on an unpredictable path as well, not a all a good thing.
Clustering of BP or AP motors in upper stages needs to be done electronically with "staging timers", R/C rigs, and others methods.
I hope this helps,
Please only fly Safety First. The hobby you save may be your own!

 

[astronboy]

Although you cannot stage a cluster first stage to a cluster second stage, you could build a cluster first stage, and a single motor second stage....

Something like this:

1st stage: 3 C6-0s

2nd Stage: 1 D12-7

 

[SwingWing]

O.K. so what if you designed the clustered booster to be several individual stuffer tubes that each dropped away seperately as the above sustainer engine lit?
I know that this has two chances of working - slim and none, but your thoughts????

 

[astronboy]

Do you mean three 'strap on' boosters like the space shuttle?

Would you still want three upper stage motors? If so, this still will not work due to the problems Micromister mentioned.

Now, if you had say, 4 booster motors, three being strap on boosters that dropped away, and the 4th was a central motor that ignited the top stage, this would be complicated, but could conceivably work.

 

[SwingWing]

Picture a 3-motor cluster upper stage and 3 individual booster motor tubes, each with a single fin, and not connected to the others in any way. As each upper motor lights, it blows away its booster motor tube, but not the others. Figuring the time difference lighting the uppers isn't too big, and with the rocket already flying with some airspeed, the thrust vectoring shouldn't be to bad??? I'm just thinkin out loud here.

 

[astronboy]

Boy, this sounds like a pretty complicated setup to me. I really do not have enought experience to know if this would actually work or not.

 

[SwingWing]

Originally posted by mtmind
I think I may have figured out how to get past the timing issue which is the only major problem I know of. It should be an interesting flight if it works!


Peace,

Mike

I'm interested in how you can get past the timing issue???

 

[n3tjm]

I seen this work during the Team America Rocketry Challenge. 3 D12-0, to 2 or 3 D12-0, to 1 E9-6. Staging was flawless, but the rocket crashed dued to being soo heavy. It is Risky, but it is pretty cool watching.

 

[user 1400]

SwingWing got the main idea and I think it would work just fine. It would basically be a cluster rocket with boosters tied to each engine to fall separately as they each stage. My secondary idea was to put separate rockets on the front of the boost cluster. I'm not as sure of it's success rate but would make for an interesting flight.

The embodiment I'm looking at now is a bt-80 2.5 inches long with 7 bt-20 tubes. The center one would extend past the others to carry the booster's parachute. 3 of the other six would be capped while the other three would be open to stage to other motors. Three bt-20 rockets would be positioned around the outside recieving the open booster engines. When the rocket launches, seven engines light. To me this means Aerotech d-13 in the center and c6-0's around the outside. When those motors finish, the appropriate ones stage to the individual rockets, which zip off into the sky ahead. The d-13 has a delay that will allow time for the little rockets to leave but will kick out the chute before the booster hits the ground. The little rockets will be equiped with their own recovery devices, probably streamers, and come down on their own.

Yes, I know it's a tracking nightmare but the flight would be cool, and you're only going to loose the little ones which can be made fairly cheap. They're just a tube, nose cone, thrust ring, fins, and recovery.

Anyways, what do you think?

Peace

Mike

 

[Mike]

Now this is just my view but I think it sounds like a VERY advanced rocket and potentially dangerous.

Firstly you're trying to ignite 7 motors which in itself is an advanced technique, now imagine that you didn't ignite them all successfully you rocket will fly away in an unpredicted direction or go unstable, then three rocket will launch from this unstable rocket. These three rockets will be stable so should fly straight where you point them, imagine if they're pointed downwards, at you or at spectators it could do some serious damage.

You've also got practical elements to contend with, you'd be trying to launch three rockets from a very confined space. Also stability, you'll have a massive weight at the bottom so will need large fins and long rocket.

I've only raised a few points so wait for others to chime in.

As MicroMister said "only fly safety first."

 

[astronboy]

I agree with mike. This is an advanced technique. Clustering is one of the toughest skills to master. I know I have not done so.

I would suggest starting with a 2 or 3 motor version of your design. You can develop the skills and techniques needed to ensure the whole thing will work with more clustered motors. For example: If you build a BT-80 version with only three drop away booster motors, this leaves plenty of room in the unused 4 tubes of the upper stage for a recovery system for the each of the drop away boosters.

I would also suggest LARGE fins. The Fliskits Deuce's Wild has very large fins in part to ensure that the rocket will fly with only one motor ignited. ... one with planty of fin area to use as a

 

[Micromeister]

MtMind:
Doug, Mike, Astronboy, and I are trying to give you the benefit of the doubt, as well as pass along good sound experence. My decades old handle is Mrcluster, I got the tag because I would rather cluster BP motors than anything. I've been flying 3 to 7 motor clusters for nearly 30 years. In that time many modelers including myself have experimented heavily with cluster to cluster staging. the success rate is dismal. I'm going to attach a pic group of a clustered staged 7 motor combination that HAS worked with a 60 percent success rate. This models success has been marred by some pretty nasty failures. I do not fly this model anymore, It was conceved as an answer to a 4 flight competition problem back in the mid 70's called Quadrent competition, where one model HAD to be flown in 4 events. If you lost the model in one you were DQ'ed from the whole event. the model originally fleu with the 18mm type S "short 1 3/4" long standard motors, and a B or C standard 18mm motor in the core.

Back to your model, Doug mentioned the 3D12 to E9 combination being used in the Team America Challange event, we have at least two teams that qualified for the fly-offs using this method. the trick is to "funnel" the ejection gases to the upper stage motor and vent it just below the upper stage nozzle, allowing the hot sparks to enter the nozzle without the gas buildup seperating the stages. Unfortunately this method will not work with upper stage clusters for the reasons mentioned in my earlier post. You also mentioned using Aerotech D13, isn't that a AP motor? if So, that is another major NO No, never mix Bp and Ap due to the difference in ignition times. your center AP motor most likely will not be ignited before the model leaves the launcher. Exterior drop off stages, are great fun. If you have a Strong enought core motor, Staging to seperate external upper stage models is doable. (as with the TriAd see pic) Leave your Core vehicle as either single staged or at very most, if you really must stage, to a single Core BP motor.

One more very important point, This may draw a few comments but, I'll simply stand on my over 1000 clustered model success record of 97% over 28 years.
If you are going to fly clusters the ONLY Proven way to successfully ignite clusters is with a RELAY INGNITION system, Including a 12Volt High amp battery at the launcher, not the contorller. Remember Minimum of 2amps per Igniter. speaking of igniters, if you are clustering you must pretest each igniter before, during, and After each igniter is installed in the motors.
I'd like you to visit the Narhams.org web site, go to the Library section, under Tech-Tip #006 clustering BP motors, I think it will answer a lot of your clustering questions. I've had a real blast with mulit-motor models, I hope you will also. just keep it safe. If you haven't already read the thread on "clustering the classics" you may want to check it out it has a ton of info that may interest you
Happy Clustering!

I hope this helps, Heres the Pic ...Remember This model was only sucessful about 60 percent of this flights over the years,

 

[astronboy]

Micromister.... Wow! I am stunned by this one.... In the early 1980's, a local rocketeering friend of mine built a multi stage cluster of this same configuration:

4 motor lower stage cluster with lots of fin area, and a central upper stage, with three smaller rockets as outer/upper stages.

We launched this three times. each was a failure in one way or another. The best flight had two of the four upper stages ignite. The last flight was a total failure ending with the destruction of the entire rocket except two of the outer upper stages.

To change gears, I am looking at rebuilding my 'heavy duty' 12v launch system (Uses a portable automobile 'jump start' battery) to a relay system. Can you recommend a relay that will handle the appropriate amps for multiple BP motor clustering?

 

[Micromeister]

Astron:
I sure can, Most local electrical supply companies, have what are known as Power relays, I use DPDT 40amp per contact relays with a 12Volt DC coil. If you are limiting you clusters to 4 or under motors, Raido shack has a small relay that has 10amps contacts and a 12Volt D.C. coil, remember the 2 Amp per contact rule of thumb. If you will visit the Tech-tip I mentioned in the previous message you will find a downloadable report with Part numbers, Wiring diagrams and I think I included a few pic. Heres a pic of the inside of one system.
Hope this helps

 

[Micromeister]

Swingwing and Mtmind:
I did a little digging on my lunch break, I found and updated a very old 1977 "concept" drawing, while considering "Chad Staging" D13-0 motors, I would never build this beast as it was Way over the 4 oz propellant, 1 pound limit, Even by todays 3.3lb - 4.4oz propellant LMR standards it wouldn't fit, shes too dang Heavy Hopefully you may be able to see a few of the design and construction problems looking at this awful thing.
Cheap And Dirty stageing has the booster motor taped directly to the sustainer motor, when the Booster ignites the sustainer the spent booster casing falls free, No this is not a violation of the model rocket safety code! free falling cases are perfectly OK. By keeping the stage weight down and NOT attaching the booster motors to one another it eliminates one of the "Timing" problems I mentioned earlier.
This is a fun to consider but NOT a flyable design. Just wanted to show you, people have been thinking about such things for a very long time.

 

[SwingWing]

Originally posted by Micromister
This is a fun to consider but NOT a flyable design. Just wanted to show you, people have been thinking about such things for a very long time.

Thats kinda how I feel about it.

 

[user 1400]

Thanks for all the info. Believe me, the majority of these concerns had crossed my mind before I posted. But I didn't know just how low success rates had been for clusters. To put your minds at ease, these concepts have been just concepts and I don't intend to build them in the near future. I more or less was looking for confirmation as to my doubts about the reliability of clusters and staging, especially when combined.

Safety always comes first in my book, particularly concerning high speed projectiles.


Peace

Mike