Poor man's Dual Deployment

[scadaman29325]

I've been wanting to get into clusters for a while, but needed a good reason (bigger and higher just didn't do it for me).

I've got a Deuces Wild on order, should be there when I get home next week (I'm on vacation in Buffalo, NY). I thought the Deuce was a good reason, it's pretty original.

While at our last club launch, Gothica87 mentioned 'poor man's dual deployment'. Dual deployment is interesting all by itself, but poor man's d.d. really got my attention...

It seems that when you design your cluster mount, you keep in mind the use of engines with different delays, a C6-3 pops the rocket in half and a C6-7 pops the parachute out...

I can imagine a couple of extra long 24mm motor mount tubes on a dual engine cluster and a 3rd centering ring (baffle) up close to the coupling. The short delay tube packed with wadding only and the long delay tube stuffed with a chute and wadding at both ends.

Sure sounds like it would work... to be added to the top of project list.

Any concerns that I need to be made aware of...?

 

[hokkyokusei]

You probably thought of this already, but you need to make sure that the second ejection charge can't vent through the hole left in the first motor after it fires the first ejection charge.

 

[adrian]

Take a look at the Descon 11 Project Amerika. It features a cluster with the central motor ducted through a tube to ignite an upper stage, and two other motors which push a piston past that tube to deploy the parachute. You should be able to do something similar, e.g. fix the nose cone to the piston, have C6-3 outer motors, and put the parachute and wadding into the core tube.

 

[shinbone]

Scadaman,
I've been noodling with something similiar recently.
I'm considering a longer stuffer tube (the short delay) that pops the nose cone and deploys a drogue chute or streamer.
The shorter tube (the long delay) then pops the payload area (from which the nose has already separated) away from the main body tube, deploying the main chute.
It seems a bit simpler, design-wise, than your concept. If I'm missing something, by all means let me know.
This is all on paper, by the by, and I haven't actually put anything together yet.
Greg

 

[scadaman29325]

Originally posted by shinbone
...I'm considering a longer stuffer tube...
The shorter tube ...
Greg

I was thinking about both tubes being the same length, they would come to about 3" from the nosecone/payload (that's where the 3rd centering ring comes in).

the first ejection could possibly force the parachute further down its tube, but that probably doesn't matter, because the second ejection will force the chute out no matter what(?).

Maybe I'm not clear...
Dual extra long motor mounts, both motor mounts use tubes 12"(?) long in a 15"(?) bodytube... 2 centering rings where they normally go, and a third acting as a baffle to reduce pressurized volume for nose/payload ejection... first tube with wadding only, second with wadding/parachute/wadding...

 

[shinbone]

I see -- you're actually putting the chute inside the motor mount tube. Now that my light bulb has come on, your way seems simpler than mine.
Both plans seem workable to me. Time for us to get them built, I guess, then report back!
What diameter BT you thinking of working with?
You might consider a piece of Nomex to wrap your chute in as a little extra protection. Other than that, I don't see any issues beyond normal procedures to ensure stability.
Maybe someone else will think of something we've missed.

 

[scadaman29325]

Originally posted by shinbone
... Time for us to get them built, I guess, then report back!
What diameter BT you thinking of working with?...

Right now I'm thinking two BT-50 (24mm) in a BT-70.

This may wait for my L1, I could make it quad (4) for redundancy, 2 to pop the cone/payload and 2 for two parachutes. Call it my Quatro Dually 2by2.

Could do it with even 13mm motors...? I'll have to find my motor chart. And of course 18mm motors.

Maybe someone else will think of something we've missed.

I've got so many un-built kits now I'll have to wait a while. I'm enjoying coming up with ideas and filing them away for future use.

If you do decide to go ahead let me know how it turns out.

I'm just glad that someone else thinks it's a worthy idea also.

 

[Zippy]

Ummm, this may be simplistic reasoning... but what is the point of using Poor man's Dual Deploy? With Estes BP motors the drogue and main chute deploys will be within seconds of each other. It might look cool but it won't save you much of a walk.

 

[powderburner]

Zippy, I see your point, but just the same, maybe a few seconds of freefall (before chute deploy) would make the difference in successful recovery versus drifting away on the wind-----you never know

Scadaman and company, it is true that the chute might be forced deeper into its ejection tube by the pressurization of the first ejection charge. So put a lid on it. A loosely fitted plug, with a solid disc (of CR-type material?) that overhangs the edges of the ejection tube would be placed in position and tied onto the shock cord/tether line for the NC. When the ejection charge pops the NC the tether for the plug would be short enough that the NC would move maybe six inches and then yank the plug out. The first ejection charge would not have an open path to the chute, but this would open up immediately afterward. Get it? (Or is my description clear as mud?)

Another idea: the ejection tube holding the chute can be a different diameter at the front (making more room for a chute) than at the motor mount in the rear. Use a centering ring for the transition and keep the tubes aligned carefully. That way, if you want to have two 18mm motor mounts, you can still have a 24mm tube to carry the recovery system.

The biggest DISadvantage I can see to all this complexity is that your rocket will be totally dependant on successful ignition of both motors for every flight. If the first motor is the only ignition you will have a low flight, and even if the NC pops off late, you will have a hard impact. If the second motor is the only ignition you will also have a low flight, but the chute might possibly deploy very late (or, it might not). Using two MMTs vented directly to a common forward recovery bay, and using two motors with the proper delay, will increase the chances of a successful flight.

 

[shinbone]

Zippy,
Agreed that there's not much "point" to this concept, other than to see if it will work. Pure science, I guess.
Theoretically, there would be a four-second difference if launched with a C6-3, C6-7 combination. It could fall quite a ways in that time if only a streamer is deployed initially. I'm sure it will require a little fine-tuning.
Maybe the "cool factor" would be a benefit. Or maybe everyone will get a good laugh if it all falls apart. Been there, done both. They each have their rewards!
By the by, I've had 100% success igniting two-motor BP clusters (many Deuce flights!), so I'm not overly concerned about that.
Of course, it would be a "heads up" launch all the way.
Greg

 

[DPatell]

I was going to suggest making a normal, short cluster mount. Then make a piece of balsa with a width of the ID of the tube, and a length of the distance between the top CR and just short of the nosecone shoulder. Glue this between the two motor mounts and along where it contacts the tube. That will provide two semi-circular parachute bays.

Attach the nosecone shock cord to an eyebolt on the drogue side, main chute and shock cord to an eyebolt on the other side.

Very similar to your idea but may provide more space for parachutes.

Oh yea, make the drogue cord much longer, or much shorter than the main shock cord. I would suggest making the drogue cord VERY long so that the two parachutes don't pass by each other.

You still may have tangle problems with the drogue shock cord and main parachute, though...

 

[shinbone]

An elegant addition to the concept. Thanks!
Greg

 

[scadaman29325]

Originally posted by DPatell
I was going to suggest making a normal, short cluster mount. Then make a piece of balsa with a width of the ID of the tube, and a length of the distance between the top CR and just short of the nosecone shoulder. Glue this between the two motor mounts and along where it contacts the tube. That will provide two semi-circular parachute bays.

Attach the nosecone shock cord to an eyebolt on the drogue side, main chute and shock cord to an eyebolt on the other side.

Very similar to your idea but may provide more space for parachutes.

Oh yea, make the drogue cord much longer, or much shorter than the main shock cord. I would suggest making the drogue cord VERY long so that the two parachutes don't pass by each other.

You still may have tangle problems with the drogue shock cord and main parachute, though...

???
My minds picture is: a 4 engine cluster, 2 with long tubes on opposing corners for seperation blast, 2 regular mmt tubes in the other corners, longitudenal bulkhead seperating engine sets...

And you could use an RMS with up to a 12 sec delay if we went with 24mm mounts...

If we keep the opposing corners equal, we could use different loads in the seperation stage as to the chute deployment stage, even different sizes... C6-3 for seperation and an F12j-12 (3 sec burn )

uh-oh... with dual RMS, "Poor-man" just went out the window...
... and with F12 we may have to move this thread to "mid-power"

ok then, back to a pair of D12-3 and E9-8... I think Poorman/Scadaman can deal with that...

(I know (but am ignoring) that the total impulse still puts it into mid-power... two D12s plus two E9s... 20+20+30+30=100 or G)

 

[DPatell]

hmm, lemme try to explain again, I hate when I don't make sense

Basically, you have a balsa plank running the length of the tube. It's width fits snugly inside the diameter of the tube. It's length is from the top CR to just under the nosecone shoulder.

It splits the tube in half lengthwise. This way, you can use a D12-3 and a D12-7. You place the drogue chute and shock cord in the side with the D12-3, and attach that shock cord to the nosecone. When the D12-3 ejects, it deploys the drogue chute and pops the nosecone off.

The main chute is in the side with the D12-7. Since the nosecone has already deployed, when the -7 ejects, it pops the main chute and it's shockcord. The main is attached to the end of this shock cord.

Does that help at all? kinda hard to explain.

 

[scadaman29325]

Yeppers...


That might be my first proto-type (one wall)...

The next one will have have redundancy with the wall and 2 tubes or 2 walls... I would think 2 walls forming and "X" would add alot of strength (wieght?) to it

I think that's a requirement for L1 or L2. I'm going to check into that now.

Thanks for the good ideas!