Forward closure question...

[Chud]

If planning on using a J180 for a LVL 2 attempt, would I need the Extended forward closure...plugged? I am using dual deployment via electronics....no motor ejection.

Thanks

 

[Area66]

you can simply replace the BP with grease and put the red cap

 

[GRIFFIN]

If planning on using a J180 for a LVL 2 attempt, would I need the Extended forward closure...plugged? I am using dual deployment via electronics....no motor ejection.

Thanks

No, just don't add the ejection charge to the closure. Install the delay for tracking smoke. It is common for people to fill the bp well with grease.

 

[Chud]

No, just don't add the ejection charge to the closure. Install the delay for tracking smoke. It is common for people to fill the bp well with grease.

Ok...gotchya. Standard forward closure. Nice tip on tracking smoke.
Thank you.

 

[DJDeadParrot]

Is the J90 the only motor that requires the extended closure?

 

[GRIFFIN]

K185 is another

 

[Wizard]

Is the J90 the only motor that requires the extended closure?

There are four AT motors that use the extended closure- J90, J135, K185, and the K270, all White Lightning, in the 54/852, 1280, 1706, and 2560 cases, respectively. They all have a square notch (somewhat like a very shallow c-slot) in the side of the grains rather than an offset core like a moonburner. The J180T (in the 852 case) uses the same geometry, but the much shorter burn time allows the standard forward closure.

David

 

[Onebadhawk]

There are four AT motors that use the extended closure- J90, J135, K185, and the K270, all White Lightning, in the 54/852, 1280, 1706, and 2560 cases, respectively. They all have a square notch (somewhat like a very shallow c-slot) in the side of the grains rather than an offset core like a moonburner. The J180T (in the 852 case) uses the same geometry, but the much shorter burn time allows the standard forward closure.

David

You are 100% correct..........
I have a J 90 W on it's way to me now......
I always use the 5/16 screw eye enclosure,,, that's a long plugged enclosure as well...........
I just verified all this with the Aerotech technical drawings of these cases,,,,,
to make sure I had the correct enclosure for the J 90 W I just purchased......

I have a question,,,,,,
I purchased this load because of it's long burn,,,,,, very cool,,,,,,,,,
I understand they get such a long burn, low average impulse by changing the grain geometry..........

What does that have to do with the delay grain ??????
why does the delay grain have to change so drastically that you need a different / longer enclosure ?????????

Teddy

 

[GRIFFIN]

Longer burn time=more delay grain needed

 

[CarVac]

You are 100% correct..........
I have a J 90 W on it's way to me now......
I always use the 5/16 screw eye enclosure,,, that's a long plugged enclosure as well...........
I just verified all this with the Aerotech technical drawings of these cases,,,,,
to make sure I had the correct enclosure for the J 90 W I just purchased......

I have a question,,,,,,
I purchased this load because of it's long burn,,,,,, very cool,,,,,,,,,
I understand they get such a long burn, low average impulse by changing the grain geometry..........

What does that have to do with the delay grain ??????
why does the delay grain have to change so drastically that you need a different / longer enclosure ?????????

Teddy

During the motor burn, the higher pressure in the case causes the delay grain to burn significantly faster than after burnout. So, when the motor burn is very long, the delay grain needs to be long so that there is still some remaining at the end of the burn.

 

[Onebadhawk]

And it's the delay grain that's sealing the top of the motor,,,,,,,
AAAAAAhhhhhaaaaaaaa,,,,,

Ok
Thank you guys,,,,

Teddy

 

[jimzcatz]

Remember the delay grain lights the same time as the propellant so it still has to be burning at the end of a 7+ second burn motor and still have some left for coast phase.

J180...4 sec burn Blue Tunder...one of my favorite motors!!