First MPR Launch, Estes Partizon Failure

[WLViking]

So I recently got back into rocketry for the first time since high school. For the last few months, I've had a bunch of successful (and several not so successful) LPR launches, and just started into MPR. Figuring that there would be a learning curve, I have built a Argent, Partizon, and Ventris as "test beds" as straight mid power builds with no high power techniques and worked through the growing pains but wanted to do some launches before I started modifying the kits for high power launches.

Today was the first time I could launch, and sure enough, I had a failure. I think I had a drag separation issue, but was hoping someone here could give me some advice and confirm the solution going forward. Here is what happened.

Weather was 20 degrees F, with a 5 mph SE wind on a snow covered field. I launched an Estes Partizon (w/ a Custom Paint job named the "Cheshire Cat") with an Aerotech Econojet G74-9W SU motor off a Mantis Launch Pad using an Interlock launch controller. The rocket cleared the pad just fine and looked great going up, but it seemed to my untrained eye like the ejection fired because I saw the nose cone separate and the parachute open. It was then clear that the nose cone, shock cord (stock from kit, elastic nylon attached via teabag 6" into body tube), and parachute (attached at nose cone loop) had separated and the body tube was falling separately. After I saw the separation, I thought I saw a puff come from the front end of the body tube while it twirled in the air and fell to its doom. Unfortunately, I don't have video but will going forward. I will post pictures shortly once I take them.

Both sections were recovered and after inspection, there was no damage to the nose cone, but the body tube had a zipper all the way to the teabag where you could see where the shock cord snapped off (teabag held just fine). Thanks the snow, the only other damage was some paint flaking and some minor scarring on one of the fins that does not even need a repair. Based on the inspection and browsing here, I came to the drag separation conclusion. With LPR, I was always concerned with making the nose cone fit too tight, so I think it may have been too loose in the BT, and the motor cutoff caused the sections to separate. It would stay put with just gravity, but using a salt shaker method I read about, it would easily come out. I intend to make it tighter going forward. I wanted to know if I need to drill vent holes as well in order to equalize pressure if I only intend to launch these with G and lower motors.

Also, does anyone know who to contact at NIRA or Prairie State Rocketry? I reached out a while ago so I could launch with other people, but didn't hear back from their website. I figure people on here are a lot more active and I am looking to meet some of you here around Chicago.

Thank you in advance for the advice!

 

[WLViking]

Here are 3 pictures. Wish I had a before picture but just picture the cat without the scar!

 

[Kirk G]

Here are 3 pictures. Wish I had a before picture but just picture the cat without the scar!

I would think you would be able to go to www.NAR.org and use the club locator function to find the latest web site information and/or email address for a club near you or near your launch site.

 

[K'Tesh]

I'm doubting drag separation. Like you hinted at, I'm wondering if the lack of venting may have played a role in this.

 

[terryg]

Sounds more likely that the motor blew the ejection charge at or near motor burn out. The fin design does not look large enough to cause drag separation.

 

[ActingLikeAKid]

Here are 3 pictures. Wish I had a before picture but just picture the cat without the scar!

Love the paint job!

 

[Tonimus]

I too am inclined to think this is an early ejection event.

 

[K'Tesh]

Love the paint job!

I'll second that... It can be fixed.

 

[d11rok]

I too am inclined to think this is an early ejection event.

I said that to my lady the other day...she was not amused :-/

 

[rstaff3]

I vote for early ejection also. The nose cone on these aren't heavy enough to drag separate unless it is crazy loose and a G-powered rocket shouldn't need a vent.

 

[marcusSRG]

After I saw the separation, I thought I saw a puff come from the front end of the body tube while it twirled in the air and fell to its doom.

I would be inclined to say early ejection like the others, but this comment makes me think the ejection charge went off after the fact. My guess is separation from pressure buildup, drag separation or a combination of the two. You specify thinking you saw a "puff," not just smoke. This makes me think that was the ejection charge going off on time. Definitely add a small pressure relief hole regardless.

 

[Construct_VA]

I'm sorry to see this happened. I am currently in the building phase of my Partizon and am curious to see what brought yours down.

 

[WLViking]

Thank you everyone for the replies! I was willing to fall on the sword but maybe that was too soon.

I would think you would be able to go to www.NAR.org and use the club locator function to find the latest web site information and/or email address for a club near you or near your launch site.

That's what I tried but got no response to. Hence why I am reaching out on here. I want to launch with active, helpful people like all of you.

I'll second that... It can be fixed.

Definitely going to try and fix it. Was thinking about smoothing out the zipper in place and applying a smooth coat of Epoxy on the face. Then sanding the interior BT to reduce any potential bulge. Structurally, I have to say, I was really impressed with the product. The BT fell over 1K feet and as you can see, the damage was minimal. Aside from the zipper, there are no visible bulges anywhere on the body and no deformations even on the front end. Kudos to Estes for making a great kit, and I do intend to fix the paint job.

I would be inclined to say early ejection like the others, but this comment makes me think the ejection charge went off after the fact. My guess is separation from pressure buildup, drag separation or a combination of the two. You specify thinking you saw a "puff," not just smoke. This makes me think that was the ejection charge going off on time. Definitely add a small pressure relief hole regardless.

This is why I wish I had the video. Aside from the 5 kids playing in the snow, there were 2 other adults with me during the launch and I was the only one who saw the puff. It may have been wadding coming out during a dip in the nose, or it could have been the cap going off. I DID find the cap in the BT when I recovered it, and most of the wadding was still in the tube. I mean, I lost next to no wadding whatsoever.

Part of me thinks that means that there was a drag separation because there was no overpressure from the cap blast to fire it all out, but if that was the case, it seems some would have fallen out when the nose cone initially pulled it down. The other half is wondering if it was an early ejection, so the rocket was travelling at max speed and the wadding was held in place by inertia. Complicating it is that the tube is 46" and I didn't build a baffle into it so the wadding could just have been sitting farther down and held in place by the acceleration. If this is the case, I am leaning more towards your suggestion of early ejection, because the rocket was horizontal after the 9 sec delay when the charge would have gone off, and I would think more wadding would have come out with no nose cone in place and no gravity, since the tube fell mostly on a horizontal axis.

Sorry for the stream of consciousness. I appreciate all of the feedback!

 

[The_Lone_Beagle]

You said:
The rocket cleared the pad just fine and looked great going up, but it seemed to my untrained eye like the ejection fired because I saw the nose cone separate and the parachute open.

Sorry, it isn't clear to me, how long after launch did the ejection charge fire? About how high do you think the rocket was? Did it reach apogee?

 

[WLViking]

You said:
The rocket cleared the pad just fine and looked great going up, but it seemed to my untrained eye like the ejection fired because I saw the nose cone separate and the parachute open.

Sorry, it isn't clear to me, how long after launch did the ejection charge fire? About how high do you think the rocket was? Did it reach apogee?

No problem. The rocket got to roughly 1K feet. I didn't have a timer out, but it was around 2 seconds it seemed to release. Almost immediately after the white plume from the white lightening engine cut out.

 

[dixontj93060]

No problem. The rocket got to roughly 1K feet. I didn't have a timer out, but it was around 2 seconds it seemed to release. Almost immediately after the white plume from the white lightening engine cut out.

How quickly did the motor light on the pad? In other words did it smoke/smolder/chuff some before taking off? If so, you may have had the delay element start to burn and, in turn, shorten your effective delay considerably.

 

[WLViking]

How quickly did the motor light on the pad? In other words did it smoke/smolder/chuff some before taking off? If so, you may have had the delay element start to burn and, in turn, shorten your effective delay considerably.

It came off immediately. There were some sparks, then the woosh of white smoke and immediate lift off. No delay on the pad and defintely not 9 seconds.

 

[K'Tesh]

Definitely going to try and fix it. Was thinking about smoothing out the zipper in place and applying a smooth coat of Epoxy on the face. Then sanding the interior BT to reduce any potential bulge. Structurally, I have to say, I was really impressed with the product. The BT fell over 1K feet and as you can see, the damage was minimal. Aside from the zipper, there are no visible bulges anywhere on the body and no deformations even on the front end. Kudos to Estes for making a great kit, and I do intend to fix the paint job.

For me, I'd try chopping off the damaged area, then use a coupler, and another section of body tube to replace it. If you didn't already do it, you could also add in a 1/2 moon baffle (or similar) and mount the shock cord to that. After that it's a little priming, filling, sanding and painting.

 

[WLViking]

For me, I'd try chopping off the damaged area, then use a coupler, and another section of body tube to replace it. If you didn't already do it, you could also add in a 1/2 moon baffle (or similar) and mount the shock cord to that. After that it's a little priming, filling, sanding and painting.

So take off about 10" and add back the 15.5" of a new tube and repaint. That sounds like it will work a lot better to me than my idea. And since it is a training rocket, I will definitely add the baffle. I was thinking of taking an extra MM retaining ring and epoxying it to the upper coupler that is connecting the piece I will be cutting to the rest of the BT and instead of a teabag, using steel eyelets I picked up at Home Depot. Once it is in place, I would attache the new coupler and BT to the remaining cut piece, meaning I would have roughly 18.5" of space between the baffle and the front end. Does that sound about right?

2 other questions:

1 - Do I need to buy a new shock cord to give me extra length? I only lost about 3" on the old one, but it was placed only 5" into the BT. at 18.5", that means my NC will have roughly 16" less free shock cord to extend on.

2 - I intend to drill overpressure holes in the BT. Where should I put them? Toward the aft end? The front end? Before or after the baffle? What has worked best for you?

 

[Tonimus]

1. I wouldn't bother.

2. I'd put them aft of the baffle, but it doesn't matter as long as they're not too big.

 

[MALBAR 70]

I had a zipper on my Partizon and I did exactly as K'Tesh suggested. I bought another Partizon(with the Estes sale they are cheap enough) to use for parts. I used one of the tubes and a coupler from the kit and have a nice bag of PSII parts for the future.
The repair came out, great the rocket is a little taller now but still flies good.