AeroTech Open Thread

[boatgeek]

I had a failure of an [edit] E18-7 [end edit] motor in a 24/40 case this weekend. It was an old (~10-15 years!) reload, and the grain was prettty swollen. I trimmed out some of the oxidation where the igniter lands, and managed to get it all together. It took some force to screw down the aft closure. I also declined to use the included copperhead starter, and instead used a Firstfire Micro boosted with a little Duco and black powder. Ignition was slow, with a couple of chuffs, including one with the rocket about 2/3 of the way up the rail. Off the pad and up in the air, the motor came up to pressure and spat the aft closure and nozzle. On recovery, the case has a notch cut out in line with the C-slot and the anodizing on the case is burned back 1/4" or so from the case end. Here's what it looks like:


So my questions:
(a) Did I do something wrong in the assembly? It looks like the aft o-ring failed. I followed the instructions to the best of my ability, but I can't discount the possibility of user error.
(b) Is this kind of failure covered by warranty?
(c) I have several other aged reloads like this one, in D to H ranges, that were left to our local high school rocketry club. Are we going to continue to have issues like this with these reloads? If so, I'm inclined to consign them to household hazardous waste rather than risk destruction of student rockets.

More info and flight video here:
https://www.rocketryforum.com/threads/traveling-rocket-thread.163279/post-2217106

 

[AeroTech]

I had a failure of an E8-7 motor in a 24/40 case this weekend. It was an old (~10-15 years!) reload, and the grain was prettty swollen. I trimmed out some of the oxidation where the igniter lands, and managed to get it all together. It took some force to screw down the aft closure. I also declined to use the included copperhead starter, and instead used a Firstfire Micro boosted with a little Duco and black powder. Ignition was slow, with a couple of chuffs, including one with the rocket about 2/3 of the way up the rail. Off the pad and up in the air, the motor came up to pressure and spat the aft closure and nozzle. On recovery, the case has a notch cut out in line with the C-slot and the anodizing on the case is burned back 1/4" or so from the case end. Here's what it looks like:
View attachment 495717

So my questions:
(a) Did I do something wrong in the assembly? It looks like the aft o-ring failed. I followed the instructions to the best of my ability, but I can't discount the possibility of user error.
(b) Is this kind of failure covered by warranty?
(c) I have several other aged reloads like this one, in D to H ranges, that were left to our local high school rocketry club. Are we going to continue to have issues like this with these reloads? If so, I'm inclined to consign them to household hazardous waste rather than risk destruction of student rockets.

More info and flight video here:
https://www.rocketryforum.com/threads/traveling-rocket-thread.163279/post-2217106

I assume you mean a D9 or an E28 as there is no E8. It seems to me to be an assembly error of some type. Never seen that exact type of failure before. Motors and reloads are warrantied for specific conditions and modes for 5 years after their date of manufacture, so that incident would not be covered under warranty.

 

[AeroTech]

I know you said it will cost to much for redocumentation and possible recertification, but would a 3 grain G25 work? Epoxy three grains together instead of two.

No. Redocumentation and recertification would still be required.

 

[boatgeek]

I assume you mean a D9 or an E28 as there is no E8. It seems to me to be an assembly error of some type. Never seen that exact type of failure before. Motors and reloads are warrantied for specific conditions and modes for 5 years after their date of manufacture, so that incident would not be covered under warranty.

Sorry, that was a mistype. It was an E18. The 5-year warranty is somewhat better than I was expecting based on the paper sheets, so this is no surprise.

Thanks!

 

[AeroTech]

Sorry, that was a mistype. It was an E18. The 5-year warranty is somewhat better than I was expecting based on the paper sheets, so this is no surprise.

Thanks!

It may be that the forward and aft O-rings were reversed, I've seen it several times with 29mm high power reloads. That could easily result in what you experienced.

 

[boatgeek]

It may be that the forward and aft O-rings were reversed, I've seen it several times with 29mm high power reloads. That could easily result in what you experienced.

OK, thanks. I'll keep a closer eye on that for next time.

 

[Ulexis]

I want to try my Turbo Vortico oddrock with the G12 and H13, should be fun.

I flew an H13 in a Turbo Vortico and it didn't go so well. It burned about 8 seconds on the ground.

 

[AeroTech]

I flew an H13 in a Turbo Vortico and it didn't go so well. It burned about 8 seconds on the ground.
View attachment 495757View attachment 495758View attachment 495759View attachment 495760View attachment 495761

Why? What was the liftoff weight?

 

[Ulexis]

I'm not sure. It's a super high drag oddrock that stops the accent after burnout. So, i assume there isn't enough impulse to keep it going up after the initial burst at ignition. Attached is a couple screen shots from a G40 flight last week. You can see the flame in the first shot, and then its basically done going up.

 

[Zman1961]

If you use the H13 you may not find it. It's got a 15 second burn.....

Yeah, I know. Of course, it loses a lot of altitude in the spin, but it might go out of sight. I might have to build one of the Art Applewhite pyramids instead.

 

[neil_w]

Yeah, I know. Of course, it loses a lot of altitude in the spin, but it might go out of sight.

Short of strapping it to an F1 I'm not sure you can ever really fly a Turbo Vortico out of sight....

 

[Zman1961]

Short of strapping it to an F1 I'm not sure you can ever really fly a Turbo Vortico out of sight....

Well, that's the hope. We will see next launch season. We typically launch these in the morning to keep ourselves occupied if the ceiling is too low.

 

[neil_w]

Well, that's the hope. We will see next launch season. We typically launch these in the morning to keep ourselves occupied if the ceiling is too low.

Video please.

 

[GlueckAuf]

I had a failure of an [edit] E18-7 [end edit] motor in a 24/40 case this weekend. It was an old (~10-15 years!) reload, and the grain was prettty swollen. I trimmed out some of the oxidation where the igniter lands, and managed to get it all together. It took some force to screw down the aft closure. I also declined to use the included copperhead starter, and instead used a Firstfire Micro boosted with a little Duco and black powder. Ignition was slow, with a couple of chuffs, including one with the rocket about 2/3 of the way up the rail. Off the pad and up in the air, the motor came up to pressure and spat the aft closure and nozzle. On recovery, the case has a notch cut out in line with the C-slot and the anodizing on the case is burned back 1/4" or so from the case end. Here's what it looks like:
View attachment 495717

So my questions:
(a) Did I do something wrong in the assembly? It looks like the aft o-ring failed. I followed the instructions to the best of my ability, but I can't discount the possibility of user error.
(b) Is this kind of failure covered by warranty?
(c) I have several other aged reloads like this one, in D to H ranges, that were left to our local high school rocketry club. Are we going to continue to have issues like this with these reloads? If so, I'm inclined to consign them to household hazardous waste rather than risk destruction of student rockets.

More info and flight video here:
https://www.rocketryforum.com/threads/traveling-rocket-thread.163279/post-2217106

In my experience, if the liner won't slide easily inside the casing when one assembles an RMS motor, and one has to use excessive torque to close the aft closure as the final assembly step, there is a very good chance that one of two things can happen, both potentially bad.

1. The aft edge of the paper liner will simply compress or crumple in place instead of sliding forward toward the forward closure. As a consequence, the forward o-ring won't compress between the forward insulator and the forward closure, leaving an air gap between the combustion area and the top of the aluminum casing. The failure to seal will allow high-pressure, super-hot gas to melt and breach the casing, blowing out the side of the casing. Or, it may cause the upper part of the casing and its threads to soften and swell under the intense heat. The swollen aluminum case and forward closure threads let go, blowing off the forward closure and blowing out everything above it--rigging, chute, and nose cone. Or...
2. The irregularly-crumpled, aft portion of the paper liner fails to seal against the nozzle, this time creating an air gap between the combustion area and the aft portion of the aluminum motor casing. Here again, intense pressure and heat melt the casing, blowing out the side of the casing, or softening and swelling the aft portion of the casing. The aft closure and swollen aft case threads let go, blowing off the aft closure.

The usual reason (maybe not your case, though) the liner won't slide easily within the motor tube is because it's out of tolerance, just a little too wide to fit into a casing that perhaps is still a bit dirty, or was manufactured a little too narrow. What works for me in this case is peeling off the white, outermost layer of spiral paper from the liner, test fitting it again within the case, and confirming that it will slide forward slightly when one applies the final turn or so to the aft closure, completing assembly. This ensures that both the forward and aft o-rings are properly and evenly compressed and will seal off the combustion area from the thin aluminum skin of the Aerotech casing.

 

[StreuB1]

Yes, I used a tailcone aft closure. I wasn't familiar with the medusa nozzle and didn't know to avoid the pairing - thanks for confirming.

Tail cone likely acted like a secondary divergent nozzle section and the expansion into that space likely pulled the plume into direct contact (or near direct contact) with the cone. The cracking is normal for compression molded glass phenolic BMC nozzles exposed to long burns.

 

[cwbullet]

One suggestion on motor instructions: I have seen quite a few CATOs with college teams. One thing I have noticed as a common theme is them interpreting the instructions for assembly. They read the details on the delay/smoke grain and leave it out because they are using electronics. Although not every time, it can create a nice fire show. Clarifying the instructions might avoid this.

 

[Antares JS]

Could someone post a drawing of an Aerotech motor with grain spacers? I'm using grain spacers for the first time soon and I want to be sure I get it right. I know I have seen one on here before, but I can't find it now. Specifically I will be flying a K1000T in a 75/5120 case with two spacers.

 

[mikec]

Could someone post a drawing of an Aerotech motor with grain spacers? I'm using grain spacers for the first time soon and I want to be sure I get it right.

I can't find the drawings/instructions either, but just remember that the spacer(s) should always be installed between the floating forward closure and the matching forward closure ring.

 

[Antares JS]

I can't find the drawings/instructions either, but just remember that the spacer(s) should always be installed between the floating forward closure and the matching forward closure ring.

Thanks, that's what I thought. Thanks for confirming that.

 

[DaHabes]

I flew an H13 in a Turbo Vortico and it didn't go so well. It burned about 8 seconds on the ground.
View attachment 495757View attachment 495758View attachment 495759View attachment 495760View attachment 495761

Based on Trust to Weight calculations, the H13ST's average thrust gives a 6.6 TTW ratio (TV is listed as 32g on the Rocketarium website), which should be plenty even with the TV being draggy. If thrust is > weight, then it should go up until burnout. Are you sure it was burning on the ground or was it just smoking? What was the total flight duration from launch to ground?

 

[tsmith1315]

Could someone post a drawing of an Aerotech motor with grain spacers?

29mm:

 

[StreuB1]

Can the G25 and other 29/120 reloads be used in the 29/180 case with a single RAS sleeve and the RAS end/closure?

Or must they use the 29/120 casing exclusively?

 

[waltr]

If I remember the research I did:
The loads are:
29/120 are 2Grain
29/180 are 3grain or 2g+spacer
29/240 are 4grain or 3g+spacer or 2g+2spacers
29/360 are 5grain or 4g+spacer or 3g+2spacer or 2g+3spacer

This is implied in the Reload Adapter System sheet:
"NOTE: NOT FOR USE WITH 29/60 AND 29/100 CASINGS AND RELOADS"
So for 29/120, 180, 240 & 360 cases and reloads

Note: above posted sheet doesn't have all info. Check this one dated 1-6-20.

 

[jmasterj]

29/360 are 5grain or 4g+spacer or 3g+2spacer or 2g+3spacer

29/360 are 6 grain, so to fit a 240 load you need two spacers (one std, one extended).

 

[StreuB1]

If I remember the research I did:
The loads are:
29/120 are 2Grain
29/180 are 3grain or 2g+spacer
29/240 are 4grain or 3g+spacer or 2g+2spacers
29/360 are 5grain or 4g+spacer or 3g+2spacer or 2g+3spacer

This is implied in the Reload Adapter System sheet:
"NOTE: NOT FOR USE WITH 29/60 AND 29/100 CASINGS AND RELOADS"
So for 29/120, 180, 240 & 360 cases and reloads

Note: above posted sheet doesn't have all info. Check this one dated 1-6-20.

Thank you!

 

[waltr]

29/360 are 6 grain, so to fit a 240 load you need two spacers (one std, one extended).

Thanks for the correction. It does state that on the Adapter System sheet.

 

[Sooner Boomer]

Almost all of the reloads using the Warp9 propellant require a plugged forward closure (and an altimeter for ejection). What do I do if I want to use a RAS? Can I use a standard floating closure and fill it with epoxy (JB Weld)? Would I need to fill the delay grain space, too, or just the ejection charge well?

[edit] I just looked at several of the 38mm reloads on Chris' site. The product information calls for a standard (not plugged) forward closure. It does call out that it is a plugged reload with no ejection. What about using the RAS?

 

[Scrapmaster87]

Almost all of the reloads using the Warp9 propellant require a plugged forward closure (and an altimeter for ejection). What do I do if I want to use a RAS? Can I use a standard floating closure and fill it with epoxy (JB Weld)? Would I need to fill the delay grain space, too, or just the ejection charge well?

[edit] I just looked at several of the 38mm reloads on Chris' site. The product information calls for a standard (not plugged) forward closure. It does call out that it is a plugged reload with no ejection. What about using the RAS?

The reloads come with delay grains but no charges. Assemble the motor with the delay grain in the forward closure (std or floating). I flew an I1299 last weekend, some will suggest greasing the delay grain faces. I e flown 4 warp 9 motors, all with greased delay grains. The past weekend was the fist warp 9 motor of mine that did not burn the grain.

 

[rharshberger]

Almost all of the reloads using the Warp9 propellant require a plugged forward closure (and an altimeter for ejection). What do I do if I want to use a RAS? Can I use a standard floating closure and fill it with epoxy (JB Weld)? Would I need to fill the delay grain space, too, or just the ejection charge well?

[edit] I just looked at several of the 38mm reloads on Chris' site. The product information calls for a standard (not plugged) forward closure. It does call out that it is a plugged reload with no ejection. What about using the RAS?

You use the proper closure and case, W9 reloads are boomsticks, I love 'em!

 

[Sooner Boomer]

The reloads come with delay grains but no charges. Assemble the motor with the delay grain in the forward closure (std or floating). I flew an I1299 last weekend, some will suggest greasing the delay grain faces. I e flown 4 warp 9 motors, all with greased delay grains. The past weekend was the fist warp 9 motor of mine that did not burn the grain.

OK, that's great news! There are several of these reloads I want to try out!