Clustering Propellent Types

[Moldie]

Is there a propellent type preference when clustering Aerotech composites? I would think the Blue Thunder propellent would be ideal and Black Jack would be the least ideal.

I will be using Magnelite ignitors which have proven sucessful with clustering composites for me in the past. I just have no experience clustering the Green Mojave and Redline propellents.

Thanks.

 

[ben_ullman]

I don't care what people say and think about the ease of ignition (ok, BT IS easiest) but using the right methods. ANYTHING can be lit!

Ben

 

[cjl]

Ben: have you tried Green Gorilla? I've seen thermite (from people who I trust when ignition is concerned) fail to light them, or in another case, it lit, but took over 4 seconds (despite the large thermite igniter). Now, as far as AT is concerned, I wouldn't try blackjack, but Mojave Green is quite easy to light, and Redline isn't bad either. I wouldn't worry with either of them.

 

[Moldie]

Thanks for the info!

Moldie

 

[Mike Di Venti]

I successfully lit 3 Aerotech J825 redines at our june launch(METRA)
The 5.5" dia. rocket went to 5319ft per Perfect Flite MAWD.
I had also used the long delays for motor backup.
The rocket weighed 24#s and snapped off the pad like it weighed 2#s.
She probably came close to mach


I did prep the top grain of each motor though.
1. used 60grit sand paper in the core and on the ends.
2."painted" magnalite pyrogen in core about halfway
3.used 3/4 gram thermite ignitors

maybe a little overkill, but I didn't need one of those to come up to pressure late

 

[SpartaChris]

Ben: have you tried Green Gorilla? I've seen thermite (from people who I trust when ignition is concerned) fail to light them, or in another case, it lit, but took over 4 seconds (despite the large thermite igniter). Now, as far as AT is concerned, I wouldn't try blackjack, but Mojave Green is quite easy to light, and Redline isn't bad either. I wouldn't worry with either of them.

If thermite didn't light, then something was obviously wrong. I've never seen the Gorilla Green here (Not certed in CA) but I've never once seen thermite fail to light something, when mixed and sized properly.

If the motor is taking that long to pressurize, it's likely due to having too big a thermite charge. The rapid pressure loss after the thermite burns out can extinguish AP motors, or severely slow down the rate of ignition.

You also have to prep your grains and remove any release or oxidization that may be present.

 

[SpartaChris]

Is there a propellent type preference when clustering Aerotech composites? I would think the Blue Thunder propellent would be ideal and Black Jack would be the least ideal.

I will be using Magnelite ignitors which have proven sucessful with clustering composites for me in the past. I just have no experience clustering the Green Mojave and Redline propellents.

Thanks.

BJ motors are binder rich, which gives them that thick smoke. It's also the reason why they are harder to light, but not so hard they'll fail on the pad. If you're using all the same types of motors in your cluster, you shouldn't have problems. Things get complicated when you use different propellants in your cluster.

My biggest concern with your igniters would be having one or two light while one doesn't. With higher current igniters, this can be a problem. You probably want to check the resistance of the igniters you'll be using and make sure they're all about the same. You can also look into things like the cluster buster Quickburst makes. It's designed for applications such as these.

Probably the easiest way to do it would be to pop some pyrodex pellets in the top and use an e-match to light them. Make sure you sand all of your grains a bit with some 60 grit paper to remove any release and expose fresh AP. Otherwise, things should be good to go!

 

[cjl]

If thermite didn't light, then something was obviously wrong. I've never seen the Gorilla Green here (Not certed in CA) but I've never once seen thermite fail to light something, when mixed and sized properly.

If the motor is taking that long to pressurize, it's likely due to having too big a thermite charge. The rapid pressure loss after the thermite burns out can extinguish AP motors, or severely slow down the rate of ignition.

You also have to prep your grains and remove any release or oxidization that may be present.

I would bet quite a bit of money that the thermite was done properly. Two different people, both of whom are among the most experienced EX and motor guys I know, had ignition failures or slow ignition with Green Gorilla. Every other motor I have seen them light (including a couple of O and P motors) came up to pressure instantly, without the slightest hint of a delay. That includes white lightning, blue thunder, skidmark, redline, and several EX formulations.

Aerotech's Mojave Green, on the other hand, seems to light without much trouble at all. I haven't had difficulty with it.