Need some K1103-X knowledge to help with a problem.

[mhanna]

A NASA SLI team I am working with is using an Aerotech K1103-X motors for their entry. 1st flight was perfect, no motor issues. The 2nd flight not so much, we had a blow-bye of the smoke grain causing the rocket to separate early. Here are the particulars:

• fuel grains were bonded in place with the suggested Elmers glue.
• there is no damage to the motor tube, seal disk, rear closure, and even the phenolic liner is fine.
• the forward closure whole to ignite the black powder is now about 1/2" in diameter. there was no black powder in the motor as they are using full dual deploy.
• the cardboard delay element liner is burned in several places, the delay liner o-ring looks fine, the forward rubber washer is there but burned much smaller in size now.
• the rocket lifted between 500' - 1000' then split apart.
• the only thing that wasn't done was a "breather" hole in the igniter holder. Could this have caused it to over-pressurize at ignition and blow past the smoke grain immediately?

Any ideas would really help. I haven't filed a mess report yet.

 

[rfjustin]

A NASA SLI team I am working with is using an Aerotech K1103-X motors for their entry. 1st flight was perfect, no motor issues. The 2nd flight not so much, we had a blow-bye of the smoke grain causing the rocket to separate early. Here are the particulars:

• fuel grains were bonded in place with the suggested Elmers glue.
• there is no damage to the motor tube, seal disk, rear closure, and even the phenolic liner is fine.
• the forward closure whole to ignite the black powder is now about 1/2" in diameter. there was no black powder in the motor as they are using full dual deploy.
• the cardboard delay element liner is burned in several places, the delay liner o-ring looks fine, the forward rubber washer is there but burned much smaller in size now.
• the rocket lifted between 500' - 1000' then split apart.
• the only thing that wasn't done was a "breather" hole in the igniter holder. Could this have caused it to over-pressurize at ignition and blow past the smoke grain immediately?

Any ideas would really help. I haven't filed a mess report yet.

What does this mean? "The only thing that wasn't done was a "breather" hole in the igniter holder. Could this have caused it to over-pressurize at ignition and blow past the smoke grain immediately?"

Are you referring to the pink/purple nozzle cap? Meaning you put a hole in that cap, correct? If so, that would not be the root cause here.

Also, pics may help.

 

[Handeman]

If they are not going to be using any motor ejection, you might want to consider a plugged fwd closure to put the delay grain in. It will still give you the smoke trail, but eliminate the possibility of blow by and the failure you had.

 

[mhanna]

yes, the pink/purple cap. the hole was NOT cut in it, that got bypassed.

Pictures maybe later tonight, just got back from the field.

 

[mhanna]

Yes, they are ordering a plugged closure. Still curious what caused it though.

 

[mikec]

Was the forward seal disk installed? What condition is it in? You reported it had no damage, was it sooty as they usually are, or fairly clean?

 

[rcktnut]

Did you use the same case for the second flight? If so, was it well cleaned before second flight, especially the delay well, forward closure?

 

[3stoogesrocketry]

A NASA SLI team I am working with is using an Aerotech K1103-X motors for their entry. 1st flight was perfect, no motor issues. The 2nd flight not so much, we had a blow-bye of the smoke grain causing the rocket to separate early. Here are the particulars:

• fuel grains were bonded in place with the suggested Elmers glue.
• there is no damage to the motor tube, seal disk, rear closure, and even the phenolic liner is fine.
• the forward closure whole to ignite the black powder is now about 1/2" in diameter. there was no black powder in the motor as they are using full dual deploy.
• the cardboard delay element liner is burned in several places, the delay liner o-ring looks fine, the forward rubber washer is there but burned much smaller in size now.
• the rocket lifted between 500' - 1000' then split apart.
• the only thing that wasn't done was a "breather" hole in the igniter holder. Could this have caused it to over-pressurize at ignition and blow past the smoke grain immediately?

Any ideas would really help. I haven't filed a mess report yet.

From the front down, was it flat washer/ oring/ white delay insulator tube? How loose was the white delay insulator? If it was too loose, it's possible the flame front went around the insulator tube and burnt out both sides. The white insulator tube should be tight and greased. If there's no ejection being used, liberally shmear grease on the forward closure delay element. Stuff happens, I'm sure this was simply a instance of not knowing.

 

[David Schwantz]

Does the k1103 use the spacer in the delay grain, and if so, was it in place?

 

[mhanna]

Was the forward seal disk installed? What condition is it in? You reported it had no damage, was it sooty as they usually are, or fairly clean?

Yes it was installed. It was very sooty. Its o-ring was intact with a slight blemish. The phonic tube doesn't looked to have leaked.

 

[mhanna]

Did you use the same case for the second flight? If so, was it well cleaned before second flight, especially the delay well, forward closure?

same case it was cleaned with baby wipes and appeared clean. Can't prove that now though.

 

[mhanna]

From the front down, was it flat washer/ oring/ white delay insulator tube? How loose was the white delay insulator? If it was too loose, it's possible the flame front went around the insulator tube and burnt out both sides. The white insulator tube should be tight and greased. If there's no ejection being used, liberally shmear grease on the forward closure delay element. Stuff happens, I'm sure this was simply a instance of not knowing.

Thats the big question. It was a good firm push to get the smoke grain assembly in. But was that just because of the o-ring? Can't say exactly how tight the white insulator was but it is charred on the inside and outside. I would say badly. It defiantly got on the outside and around. It wasn't sloppy lose but probably loose enough I would say. The rubber washer was burned badly too.

 

[mhanna]

Does the k1103 use the spacer in the delay grain, and if so, was it in place?

No spacer in the delay. Working on getting pictures.

 

[David Schwantz]

I just opened up a K1100T, it uses the same delay grain, and there IS a spacer that needs to be used in the load. If you did not include spacer in the reload, that is the cause of your blow by as there would be 0 pressure on the delay grain when assembled.

 

[rcktnut]

Definitely needs an aft delay spacer. https://d11fdyfhxcs9cr.cloudfront.net/templates/170652/myimages/54_1706x_k1103_1642719232130.pdf

 

[mhanna]

I just opened up a K1100T, it uses the same delay grain, and there IS a spacer that needs to be used in the load. If you did not include spacer in the reload, that is the cause of your blow by as there would be 0 pressure on the delay grain when assembled.

I'm not sure about that? The delay grain is longer that the white cardboard tube by the exact width of the o-ring. The delay grain bottom is flush with the bottom of the white cardboard tube, no room for any spacer to fit. I will double check that on the next one we use but I didn't see any extra parts.

 

[mhanna]

Pictures attached

 

[3stoogesrocketry]

I just opened up a K1100T, it uses the same delay grain, and there IS a spacer that needs to be used in the load. If you did not include spacer in the reload, that is the cause of your blow by as there would be 0 pressure on the delay grain when assembled.

K1275 I just put together yesterday does not.

Pictures attachedView attachment 633257

There should not be that much charring on the outside of the delay grain white insulator tube. I'm going to speculate the flame front went around the insulator tube and lit the front of the delay grain, instantly blowing the charge.

 

[mhanna]

Well, I found the instructions and it mentions aft delay spacer. But under QTY it says "1 or none" So now I'm really not sure if I missed it or there isn't one.

 

[mhanna]

K1275 I just put together yesterday does not.


There should not be that much charring on the outside of the delay grain white insulator tube. I'm going to speculate the flame front went around the insulator tube and lit the front of the delay grain, instantly blowing the charge.

There was no charge, it just burned into the lower section of the rocket for a while before eventually popping it apart.

 

[mhanna]

At this point I'm guessing the white tube was just not tight enough.

 

[David Schwantz]

If you look at assembly drawing you will see that it shows the delay grain extending out of #12 delay insulator and going into # 17 o ring. It also shows # 10 aft delay spacer in place. If that was left out then you have no pressure on delay grain to # 16 forward delay spacer. This allowed flame to around insulator, as seen by burn marks, into ejection well.

 

[cerving]

At this point I'm guessing the white tube was just not tight enough.

That is not uncommon. Using a plugged forward closure with electronic deployments is a good way to prevent against delay grain blowback.

 

[mhanna]

If you look at assembly drawing you will see that it shows the delay grain extending out of #12 delay insulator and going into # 17 o ring. It also shows # 10 aft delay spacer in place. If that was left out then you have no pressure on delay grain to # 16 forward delay spacer. This allowed flame to around insulator, as seen by burn marks, into ejection well.

Yes, I get that but what I'm saying is the delay grain does stick out with no room for a spacer #10. The QTY for #10 also says "1 or none". I'm thinking Aerotech has alter the delay grain to possibly not need the spacer anymore. We have one more motor as soon as I can get my hands on it I plan to open and inspect it for a spacer.

 

[David Schwantz]

let us know if new reload has spacer.

 

[AeroTech]

Yes, I get that but what I'm saying is the delay grain does stick out with no room for a spacer #10. The QTY for #10 also says "1 or none". I'm thinking Aerotech has alter the delay grain to possibly not need the spacer anymore. We have one more motor as soon as I can get my hands on it I plan to open and inspect it for a spacer.

The K1103X includes CRDK-8 which uses a 0.230” long green spacer.
https://d11fdyfhxcs9cr.cloudfront.net/templates/170652/myimages/54mm_rmsp_crdk_instr 10-27-20_1656450733910.pdf

There is also this motor assembly drawing which shows the spacer though the length has been adjusted slightly since 2011:
https://d11fdyfhxcs9cr.cloudfront.n...ges/54-1706_k1103x-14a_assy_1648847869302.pdf

 

[cbrarick]

no spacer, no o-ring seal from the seal disc to the delay assembly. All downhill from there :<
once a little gas gets through, a lot will follow.

How's the rocket?

 

[rcktnut]

One more question, did you assemble both motors? I know with a team could get distracted but loading 2 of the same motors should remember if there was a spacer or not in the first one.

 

[DAllen]

Does the K1103 require a stainless steel seal disc?

 

[David Schwantz]

In the diagram from above it lists it as 54FSD, does not mention Stainless Steel.