Cluster booster

[dragon_rider10]

I'm considering a BT-80 based 2-stage bird. I'd like to have it able to fly single stage on 24mm composites or staged with BP. Would it be possible to cluster 4x 18mm staged to a single 24mm? I'm wondering about the reliability of staging the partially aligned engines.

Anyone successfully fly anything similar?

 

[CF-105]

Sounds suspiciously like one of my early RockSim designs (which I never did build).

In theory, there is no reason you can't do it. Some things to keep in mind:

- If some of the booster motors fail to light, the rocket could be significantly off-vertical when the staging event occurs. This could be a safety issue, and well as lead to a lost or destroyed sustainer.

- To light a composite sustainer motor, you'll need some sort of onboard electronics.

 

[Handeman]

You should be able to to that, if you can construct a way of funneling the hot particles to the 24mm motor. The easiest way would be to do a 3 or 5 motor cluster and have the center motor ignite the 24mm above it. If that center motor doesn't light.......

 

[gpoehlein]

If you gap stage the rocket, you shouldn't have much trouble lighting the second stage. That said (and to elaborate on what CF-105 said), your best bet would be to stage to either an Estes D12 or E9 - not to an Aerotech motor. If you want to stage to a composite motor, you'll have to light it with an altimeter and igniter. But gap staging four C6-0 motors to an E9 should work just fine. Check the various resources Jimz, YORS and/or Ninfinger to find the Centuri technical paper on gap staging (I think it's on Jimz). Funnel the particles and heat to the second stage, vent it so it doesn't blow off from the pressure and it should work fine.

 

[Bazookadale]

- If some of the booster motors fail to light, the rocket could be significantly off-vertical when the staging event occurs. This could be a safety issue, and well as lead to a lost or destroyed sustainer.

Also remember that if a booster motor doesn't light there is the chance that the sustainer exhaust could ignite it from the wrong end and it will burn all the way down - neat to watch but a fire hazzard - saw this many times at the first 2 TARCs

 

[dragon_rider10]

Also remember that if a booster motor doesn't light there is the chance that the sustainer exhaust could ignite it from the wrong end and it will burn all the way down - neat to watch but a fire hazzard - saw this many times at the first 2 TARCs

Good to know! Flaming boosters of doom should be avoided.

I was never planning on staging BP to composite. The composite flights were all going to be single stage.

Thank you for the advice.

 

[gpoehlein]

I was never planning on staging BP to composite. The composite flights were all going to be single stage.

I kinda figured that from what you said, but in a forum this widely read, it never hurts to expand on the basics in case someone else may not know that you can't ignite composite from BP. Looking forward to seing some pics of your build and the flights!

 

[n3tjm]

Back in the days of thermalite you could stage BP to composite (and there were a few composite motors with 0 sec delays for this pupose). A piece of thermalite was sheathed in a plastic tube with both ends exposed. One end stuck out the nozzle of the composite motor, while the other went inside the motor with another piece of thermalite or propellant taped to it. The thermalite will burn almost instantly sheathed. So the D12-0 would ignite the thermalite, and a split second later the thermalite will ignite whats on the other end, and that will hopefully start the motor. NCR had a kit that flew this way.

 

[El Cheapo]

How big will the sustained be? For bt80 you could also do 2,3 or 4, 24mm cluster.

 

[Bazookadale]

Back in the days of thermalite you could stage BP to composite (and there were a few composite motors with 0 sec delays for this pupose). A piece of thermalite was sheathed in a plastic tube with both ends exposed. One end stuck out the nozzle of the composite motor, while the other went inside the motor with another piece of thermalite or propellant taped to it. The thermalite will burn almost instantly sheathed. So the D12-0 would ignite the thermalite, and a split second later the thermalite will ignite whats on the other end, and that will hopefully start the motor. NCR had a kit that flew this way.

Yes the -0 composites. One of my worst memories was a 2 stage composite that lit nose down at a SPAAR launch above the pig farm at Cocalico. Fortunately no bacon was injured.

 

[dpower]

I've staged 3x18mm to 2x24mm, just for kicks, about 2" gap. Needed a bit of staging augmentation to work reliably

 

[dragon_rider10]

How big will the sustained be? For bt80 you could also do 2,3 or 4, 24mm cluster.

I considered clustering both stages, but I want to use the main airframe for a lvl-1 cert, so I want to keep it 24mm minimum. I'm assuming there's a 24mm H somewhere but I guess I need to verify that before I get too far along.

The main airframe will be 36" in length plus the nose. I've got some scrap BT-80 for the booster.

Booster airframe in the neighborhood of 10" in length. With that, it would have maybe 6.5" in gap for the stage. Maybe a stuffer tube of Bt55 in the forward part of the booster to channel the majority of the gas into the sustainer. That would also give me a chance to add a recovery system to the booster.

 

[gdiscenza]

The largest 24mm reload I have heard of is a 6-grain CTI G150 Blue Streak. Since you cannot certify L1 with an EX motor, I think you'll have to use a 29mm motor.

G.D.

 

[KDRaven]

When I built up my Big Daddy for staging I looked into using 18mm motors and for the weight of the 4 motors vers the thrust of them I ended up staging 4-A10's (13mm) clustered around a D12-0 and staged to a 12-0 to a D12-5.

I have seen a 2 or 3 stage 24mm to a single 24mm and it used gap staging and worked fine.

 

[dragon_rider10]

The largest 24mm reload I have heard of is a 6-grain CTI G150 Blue Streak. Since you cannot certify L1 with an EX motor, I think you'll have to use a 29mm motor.

G.D.

Hmm...

Good to know. Will have to revisit these plans.

 

[El Cheapo]

If you are looking for a fairly easy rocket, the Executioner is L1 capable by modifying the centering rings and laminating the fins. IDK if Id go much more than a small 29mm H but it'll do the job. My sons 2-stage Executioner flies great on d12-0 to d12-5. Had I built it 29mm I would have no problem sending it up on an H128.

 

[CF-105]

Yes the -0 composites. One of my worst memories was a 2 stage composite that lit nose down at a SPAAR launch above the pig farm at Cocalico. Fortunately no bacon was injured.

Brings back memories of LDRS 24 and the N to N two-stage that had the booster CATO. The sustainer motor lit while the upper section was in a nose-down attitude, and headed for a herd of cattle. No bovines were injured, but the sure moo-ved! (a friend still jokes that those were the only Alberta beef to make it across the border that year).

 

[dragon_rider10]

If you are looking for a fairly easy rocket, the Executioner is L1 capable by modifying the centering rings and laminating the fins. IDK if Id go much more than a small 29mm H but it'll do the job. My sons 2-stage Executioner flies great on d12-0 to d12-5. Had I built it 29mm I would have no problem sending it up on an H128.

Remember that the rocket also has to be recovered....


No, not necessarily looking for easy, primarily looking for a way to use up my store of excess BT-80!

Maybe I'll L1 on something else, and do this one up all BP too.

 

[El Cheapo]

I pulled a Rocksim file from EMRR and ran it on my OR. That file sims out to 2,523 on an H128-10, 15.6oz with motor and 8.05oz w/out motor. Seems a little light to me. Not to mention, if you ad ply centering rings and mid-break baffle, that should ad some weight as well.

I'd say that's a nice L1 flight.

 

[dragon_rider10]

ElCheapo,

In your sim, at what altitude does the ejection occur?

 

[El Cheapo]

Looks like about 2,300'. Keep in mind, this is a copy I pulled from EMRR. I did not design the file. I'm guessing it's pretty close to what Estes would consider a stock build.

 

[tbzep]

The cool thing about a gap staged clustered booster is that you only need one (or two to be safely redundant) booster motor(s) to ignite the upper stage. The remaining booster motor(s) can have an ejection charge so that you can bring the booster down via parachute. The Launch Pad Nike Hercules kit was designed to recover the booster this way, IIRC.

For any motors that you don't plan on using to ignite the sustainer, stuff some wadding down in the top to help prevent ignition from the wrong end if it didn't ignite at the pad.

Test your igniters beforehand and be extra careful installing them. Use a good 12v launch system. Take photos before launch...If you don't, it will always crash.

 

[Handeman]

Maybe I'll L1 on something else, and do this one up all BP too.

That would be my recommendation. If you build a L1 rocket to cert with, build a L1 rocket, not a beefed up MPR that can handle an H. Once you cert and want to fly L1 motors, why not use your cert rocket instead of having to build another. My recommendation for a L1 cert rocket is something about 3 - 5 lbs and 38mm MMT. I would look for about 2,000 ft on a full H motor.