Ahh, I see now. I would think that containment would have been enough, but I do think that maybe the glass coupler bound. I'd be surprised if the charge were the problem, given your charge system.

Wow - that is a lot of re-kitting of parts. Your containment seems to be well thought out. I know a few people who use surgical tubing with great success...maybe if you have redundant charges you can have one set with centrifuge tubes and one with surgical tubing. Cover both bases.

For a long time I've been trying to figure a way to deploy laundry better. The Estes way of pressurizing a body tube doesn't scale up very well. A piston helps quite a bit getting the laundry out, but still you are pressurizing a decently big volume.

I saw in Volume 2, Issue 1 April 2007 of Rockets magazine something called a Z-PaRD. I've got one built, but still working out the logistics. You take a 1/2" aluminum tube and then a corresponding 3/8" aluminum rod. Put your charge inside and seal one end. When it goes off the rod goes flying out of the tube. You attach the tube to the bulkhead and rod to the other end (nosecone, another bulkhead, etc). You are not pressurizing a big volume and you have a very repeatable amount of force you can apply to the two parts. I've built one and tested it quite extensively. It works. My small one (about 6" total length) will throw a brick 10' into the air. My only bug to work out is how to pack everything around that center rod that is now in your rocket. I'll be building mock-ups soon of it and then I"ll be using it in a re-do of my L3 rocket (I think I can squeeze 30k out of the M900) if I can make myself happy with a solution on the center rod.

Edward

Edward,
Very interesting, never heard of the Z-pard but makes sense, however I can see how the center rod could be a major PITA and an additional potential cause for failure due to recovery elements becoming twisted.

I had considered using Rouse tech CO2 deployment devices rather than BP but I read a nice write up of some home experiments comparing BP and CO2 to 100,000 simulated feet. You can view it here:

http://www.spacewarptechnology.com/SWT/High%20Altitude%20Tests/TABLE_CONTNETS.htm#experiment4

Kinda made me feel ok sticking with the BP.
-Sean

Contained properly BP is a great choice. Less bulky, has plenty of punch, easy to handle and use.

http://www.libertylaunchsystems.com/RocketsMagazine/Issue0007/sample.pdf

At the end of that PDF you can see the author's Z-PaRD. Mine doesn't have that shackle on the left side - just screws in to the bulkhead.

That is the sticking point for me on it. How do I pack around it? Do I make my parachute into a snake and put it into the biggest chute protector ever and wrap it loosely around it? Do I go naked with the chute and just have plenty of cord on top. I have found that during testing if I sleeve the contraption in 3/4" Tubular Nylon longer than the device then it pulls over the gap and you get no black powder/hot gasses escaping onto your chute.

Edward

Adrian if you can somehow pull some data off of these that would be amazing:

Ouch. Your data is on the part that used to be attached to the pads labeled "U$9" and is apparently now somewhere in a deep hole. 🙁

All my sympathies Sean... such a gorgeous project, such a nice Up part to the flight. All my best on your next try.

Warren

Information like this is invaluable to me. It gives me insights to issues I am very foggy in understanding.

The pictures were amazing.

Sorry about your rocket. It was gorgeous.

Sean - how high was flight #1 vs. flight #2? did you go appreciably higher on the second boost?

The gremlins come out and play at mach 2+ and ~20K altitude... it took me a few swings at the plate to get efficient up there.

I've used this to over 40K MSL http://www.wimpyrockets.com/page16.html with clean recovery (and 62K MSL w/o clean recovery - but the charges worked)

With the experiences of folks like John Wilke and various sundry others I found on the web, the ONLY BP charges I do now are surgical tubing... Won't even bother with anything else. My L3 deployed flawlessly.

W

Sean,

The Raven data for your 1st flight showed 18K alt with the baro and 21K with the accel data.

After reading everyone's ideas about the failure of the second flight I would think the idea that the fg coupler caused a binding issue is top of the list. The only problem I see with that is that you said the coupler seemed to slide into the airframe easily when you assembled it for the 2nd flight.

With the heat of the burn could have the all thread and harware have warped which caused the fg coupler to bind?

As you know my 3" coupler has a similar design. Although my flight was successful I have to wonder how close I may have come to having the very same issue.

Guys, had the coupler been the only thing in the rocket, I think "binding" would be the prime suspect. The game-changer here is that Sean used the motor for the coupler, and the section of glass coupler was on top of that. I mis-read the setup earlier when I suggested the short coupler may have caused the binding.

I think with the motor as a coupler and the extension on top of that, there isn't any real way that the coupler bound. I've flown that setup many, many times with success.

Unreleated note - Why would the accel and baro be so far apart? On a very corkscrewed flight you'd expect some variance - but Sean's boosts were very straight. Even on a corkscrewy flight, you shouldn't have a delta of several thousand feet...

Unfortunately we never pulled data off the other Raven for the first flight as the way it was mounted to the board required removal to access the data port, so we just figured we'd download it after the second flight - you can guess from the photo above that this proved to not be possible.

Also of interest is the Garmin DC-20 transmitted flight data from the second attempt to the handheld, allowing the data to be downloaded and get the altitude. What was interesting was data from the first flight was not on the handheld unit, or it was overwritten by the second flight.

For my L3 take 3 I've decided to rebuild the 98 goose, however I may change some of the design components, possibly doing a more traditional design using the ebay as the coupler and I am considering using a Zpard for the apogee separation. When you think about the physics of it seems like a much more reliable method of separation, however again it has its own separate issues as well. -Sean

Sean,

Contact me about the Z-pard - I've got one made and the packing issues have vanished 🙂

Edward

care to post a picture of the Z-pard? Came up with very little on Google, other than edward himself at http://www.rocketryforumarchive.com/showthread.php?t=6715&page=3

BAsically a Z-pard is a small device that uses a metal piston to deploy the nosecone. You are using basically a 1/4" tube and piston and use a tiny amount of BP. I saw it in ER and have been constructing one for my next rocket.

Edward

I'm having trouble visualizing...