My College Tuition MkII

[BsSmith]

About a year ago I purchased a 4" Vindicator from Wildman, and over the summer I built it and ended up naming it "My College Tuition." It was meant to be a rocket that would fly reasonable distances on 54mm motors, and would eventually serve as a test platform for large EX loads. Last Saturday at Midwest Power 10, I loaded up an EX 6 grain blue motor for it's first flight. Due to unseen issues in the propellent processing, My College Tuition blew up without even leaving the pad, and I didn't even get a cool picture of it. The majority of it turned into confetti. Out of the entire rocket, the only reusable pieces are the nosecone, upper tube, and fins.

Instead of throwing those pieces in the dumpster and forgetting that the entire project ever happened, My College Tuition will be rebuilt. The only thing that I have to decide is how I will do it. I could rebuild it to the original Vindicator specifications and have the same size rocket back, but I'm leaning toward going the extreme route. It would be rebuilt with a 75mm motor mount, tip to tip reinforced fins, and a longer booster tube. If I did this, it would still be able to fly on the larger 54mm reloads, but it would also give the option to use larger Ls. The other thing to consider is that if I have the rocket available and I find a good enough sale, I'll also be able to do my L3 with it.

Of course, I would only be able to work on this over holiday breaks, so it probably won't be started until well into next year.

 

[Rocketbuilder]

I'm sorry to hear about your loss. Good on you for rebuilding though.

Oh, and I love the name! :lol:

 

[tbonerocketeer]

About a year ago I purchased a 4" Vindicator from Wildman, and over the summer I built it and ended up naming it "My College Tuition." It was meant to be a rocket that would fly reasonable distances on 54mm motors, and would eventually serve as a test platform for large EX loads. Last Saturday at Midwest Power 10, I loaded up an EX 6 grain blue motor for it's first flight. Due to unseen issues in the propellent processing, My College Tuition blew up without even leaving the pad, and I didn't even get a cool picture of it. The majority of it turned into confetti. Out of the entire rocket, the only reusable pieces are the nosecone, upper tube, and fins.

Instead of throwing those pieces in the dumpster and forgetting that the entire project ever happened, My College Tuition will be rebuilt. The only thing that I have to decide is how I will do it. I could rebuild it to the original Vindicator specifications and have the same size rocket back, but I'm leaning toward going the extreme route. It would be rebuilt with a 75mm motor mount, tip to tip reinforced fins, and a longer booster tube. If I did this, it would still be able to fly on the larger 54mm reloads, but it would also give the option to use larger Ls. The other thing to consider is that if I have the rocket available and I find a good enough sale, I'll also be able to do my L3 with it.

Of course, I would only be able to work on this over holiday breaks, so it probably won't be started until well into next year.

What were your unforeseen issues with propellant processing?

 

[BsSmith]

What were your unforeseen issues with propellant processing?

I think that it was either voids/dry spots in the grains or the bottom grain collapsed and plugged the nozzle. I had tested some 38mm loads from the same batch to a higher Kn than the one that was in this motor and they worked perfectly, but my packing process for 54mm casting tubes still seems to be a bit off. The bottom grain also had a 1" core, and in hindsight I did not use very much glue to bond it to the liner.

Oh well, I learned something, and I will try to do better the next time.

 

[justice_purdue]

It was very heartbreaking to see the motor pop.

I did capture a bit of the cato on video. [I had a GoPro set up 10 feet away from the rocket - I was filming an adjacent rocket]

https://www.youtube.com/watch?v=PO0Lr-3CpvM&feature=youtu.be

good luck with rebuild!

 

[tbonerocketeer]

I think that it was either voids/dry spots in the grains or the bottom grain collapsed and plugged the nozzle. I had tested some 38mm loads from the same batch to a higher Kn than the one that was in this motor and they worked perfectly, but my packing process for 54mm casting tubes still seems to be a bit off. The bottom grain also had a 1" core, and in hindsight I did not use very much glue to bond it to the liner.

Oh well, I learned something, and I will try to do better the next time.

What kn did you run it at?

 

[BsSmith]

It was very heartbreaking to see the motor pop.

I did capture a bit of the cato on video. [I had a GoPro set up 10 feet away from the rocket - I was filming an adjacent rocket]

https://www.youtube.com/watch?v=PO0Lr-3CpvM&feature=youtu.be

good luck with rebuild!

Thank you for that! It's more video than I have. My camera ran out of batteries, and by the time that I had it back on the rocket was already gone.

What kn did you run it at?

The motor geometry was kind of strange, with 4 long grains and stepped cores. I managed to get an initial Kn of 190 and a peak Kn of 290, with a mostly neutral burn. It simmed to be a 25% L1500 with a peak pressure of about 950 PSI. I want to try that geometry again, because it looks like it would have been an awesome motor.

 

[tbonerocketeer]

Thank you for that! It's more video than I have. My camera ran out of batteries, and by the time that I had it back on the rocket was already gone.



The motor geometry was kind of strange, with 4 long grains and stepped cores. I managed to get an initial Kn of 190 and a peak Kn of 290, with a mostly neutral burn. It simmed to be a 25% L1500 with a peak pressure of about 950 PSI. I want to try that geometry again, because it looks like it would have been an awesome motor.

Mind messaging me your formula? I am curious about it. Also, have you done the characterization of it yourself? I will send you mine if you want(ie: I dont want it to use or copy)

 

[daveyfire]

Dude, it was an AWESOME cato. We hadn't had any at the launch up until that point, so thanks for making up for it

And you're always welcome to come up the road to the house and work in our garage, if you get the urge. It's heated for winter builds!

 

[UPscaler]

Aw, sorry to see it go!

Of course...it could have just been the rocket gods saying "You know...what you really need is a three grain 75mm blue motor" :wink:


Good luck on the re-build! I for one, love fixing rockets!



Braden

 

[ECayemberg]

Brian, sorry about the cato; but glad to hear you'll rebuild it! I have an extra set of 4" Darkstar fins if you decide to go that route. Side note on only working on rockets during break... my level 3 rocket (4" Thunderbird that's flown at pretty much every MWP) was built in my dorm room. Painted in the winter down in the lounge, and various composite components cured in the lounge's oven! Where there's a will, there's a way (just don't let it mess with your schooling).

For multiple reasons, 54mm motors are my least favorite to make; send me a message if you want to discuss anything further. Mike Gross flew a 54-5G Blue on Sunday in his Fat Boy that worked well. Blues can be finicky sometimes.

Good seeing you at MWP, buddy!

-Eric-

 

[BsSmith]

I might have to start a dorm room build, then. The pieces might take awhile to get here, and I'm already a part of two rocket projects here, so it will be a slow build.

I'll have to get a copy of FinSim to see if the Vindicator fins can handle a big M, but it will most likely need more layers of composite on the fins, and possibly a layer of Kevlar cloth to dampen the vibration. I have a Rocksim file ready, and I can't help but realize that the Loki M3000 would fit almost perfectly into the booster. It's too bad that Rocksim won't be able to calculate the flight to any degree of accuracy, and I don't think that split fins are possible in RasAero.

 

[rfjustin]

Due to unseen issues in the propellent processing, My College Tuition blew up without even leaving the pad, and I didn't even get a cool picture of it.

Brian,

I was at MWP 10 for Saturday only and I did get two kick ass videos of your CATO. One pad cam, and the usual ground "up part" video. If you would like me to post said videos, please let me know.



Justin

 

[Chuck Rogers]

....... and I don't think that split fins are possible in RasAero.

Brian:

If the rocket is a single stage rocket, you can combine the two fin sets into one set of fins, with the fins having the shape of the two fins combined together. I'd just fill in the gap between the two fins.

Because the interference drag from the gap between the fins would be difficult to predict and could be large, to be conservative I'd double the fin thickness when you input the combined fin into RASAero.


Chuck Rogers
Rogers Aeroscience

 

[rfjustin]

Brian,

Per your PM, here's the video:
https://s68.beta.photobucket.com/user/rfjustin/media/QCRS/BrianSCATO.mp4.html



Justin

 

[BsSmith]

Justin,

Thank you very much for the video! It has been a huge help. I took some screen shots for it, and it seems that the motor produced two frames of regular thrust before the motor let go. The nozzle also did not seem to be clogged, so I think that the CATO was caused by a grain falling apart when the motor came up to pressure. I think that the small bits of burning propellant ejected out of the motor where pieces of this grain.

 

[REK]

I see a madcow Frenzy XL on the left . Hope the rebuild goes good and you dont get another CATO. Good luck .