News from PSFC - New videos on page 2

[reverend]

Oh Noes! Catostrophic launch failure!

Looks like the cement just ain't gonna work at the top...


The good news is the stick lived to fly again...

Some notes... Youtube really butchers the quality here. I used a high speed camera at 320x240 and 60 FPS. The high framerate looks awesome in slow-motion. I can actually see the cement plug being ejected and flying thru about 7 frames. You can hear it go 'kerplunk' when it hits the water, i moved the camera to try to capture where it landed, but I failed.

I'm pretty sure I'm on the right track with this, just need to make the motor a little bit stronger.

 

[Notebook]

Shame, but, its well and truly scorched now!

N.

 

[reverend]

I'm thinking on the next incarnation of this motor, I'll drill a few tiny holes in casing at the top and bottom for the purpose of inserting some small screws into the epoxy putty while it's soft. This means that for the plug to come out, the PVC casing will need to facture first. This should allow for sufficiently more pressure.

I'm going to build a 32 grain version of this same motor. It'll be like 1" in diameter and 5.5 feet long.:rofl:

 

[reverend]

New Grain size

 

[reverend]

T+0.000 First flame seen from nozzle end of motor
T+0.384 Flame seen from top of motor
T+1.752 End Plug ejected from top of motor, end of forward momentum, start reverse motion
T+4.472 Loss of Supersonic flow, motor burning out
T+9.410 Burnout

I believe I made an unintentional Aerospike motor. The flame burned past the epoxy along the edges of the PVC pipe, only the 2 small screws held the epoxy in until the epoxy gave way.

The small light behind the skateboard is my other camera, tripod mounted. The video from that is coming tommorow.

[ame="http://www.youtube.com/watch?v=Ij1-caJwb0Y"]YouTube - Rocket Skateboard II Rear View[/ame]


The burning skull artwork got a little toasted...

Time for a new skateboard I think. Glad they're only $10...

 

[reverend]

A new motor!

That's next to a 1 liter soda bottle.

38mm PVC (1.5") 3 KNO3-Sucrose-Sorbitol grains
Will test fire this weekend...

 

[James.Denholm]

I hope you paid for the stick and board's therapy. It's the least an employer can do.

 

[reverend]

Here's some more pics on the new nozzle/throat design.

I found this great PVC fitting, a bushing, that would be for connecting 1.5" PVC with 1/2" PVC pipe. The hole in the bushing is about 7/8" wide. By gluing and placing 2 washers in to form the throat, and using hydraulic cement to form the convergence and the divergence, we get the following...

This is a 1/4" Throat

 

[reverend]

RSB-III Prelaunch :rofl:

Launch in T-3h 10m 30s and counting...

 

[reverend]

[ame="http://www.youtube.com/watch?v=Wnyks-fAMWM"]YouTube - Rocket Skateboard III[/ame]

 

[reverend]

 

[joshb]

Reverend, thanks for the rocket motor tutorial video.

Miming it is kinda funny but works.

I'd like to see how the motor is designed and how you load the grains... do you stack them end-to-end, or with a gap? Would you ever make a hole in the center for faster burning?

How volatile are the grains, and how do you store them?

How hard is it to ignite them?

 

[reverend]

Just stack em in there... There will be a small crack seperating the grains... We definetely want this. It's in a bates burner configuration...

There is a hole drilled through the center of the grains to alter the grain geometery. Different Grain Geometeries provide different burn rates by altering the amount of surface area that's burning at any given point in time...

I had to scrub part's 2 and 3 of the last video because of some technical problems with the video itself... I'm prepping to make the two motors for use in the 4th of July rocket...

I found the greatest thing in the world today... Clear PVC Pipe.

Same Schedule 40 PVC, way more expensive ($4.50/ft), but I can only imagine how bright it would be actually seeing inside the combustion chamber... I would only use it for the special occasion... That would be quite awesome to see I think... Ordering 10ft of 1.5" tommorow

 

[joshb]

Did you make a clear PVC motor yet? Video?

 

[reverend]

Nope:

All the motors I made were fired on Jul 4th. Unfortunately, the camera we brought down had dead batteries :-( So all the efforts went undocumented.

I would like to make a clear PVC rocket at some point I'd bet it would be really bright, that stuff's wicked expensive though. I'll set aside $50 some day to buy a peice of it to experiement.

I'm going to be tied up with some other projects for a few weeks. I plan on shooting for more launches around the end of the summer.

I'm a little disappointed too, even though I took measures to ensure the humidity in my storage area remained low (ie: dehumidifier), my potassium nitrate has taken on alot of moisture... it's all clumpy now. The sorbitol seems to have started doing this too and I didn't even think it was hygroscopic.

This just means that now instead of just melting it on the griddle I get to actually cook it like it was a sugar mix. Haven't figured out yet how long I need to cook it for though.

Keep in touch.