Rocket failure to launch

[Leatherlips]

I used this article to make a BP rocket motor: http://www.skylighter.com/fireworks/how-to-make/glitter-rocket.asp a couple of weeks back, and it flew pretty well. So the same batch of fuel I used had been saved in a plastic container(with air tight lid) and I made another today.(I used an arbor press instead of hand ramming both times)

This time the rocket just sat on the launch tube and burned off the fuel then popped the header. It didn't lift off at all.

I"m wondering why this would be. Does the fuel "go bad" after a short period?

Thanks

 

[schroedinger]

No BP won't becomme bad. It is much more likely that you made something different. Maybe you had other ignition point, humidity, pressing force or header weight?

Also maybe your fuel wasn't mixed right and now you hit a spot with the wrong ratio?

How sounded your rocket? Did it try to go up or did it sound powerless?

Edited February 22, 2015 by schroedinger

[Andres1511]

You forgot the nozzle, changed something about the core specs ?

[Leatherlips]

Thanks for the replies.

I have built another and will attempt launch layer today. One thing I found was that on the initial build, I followed the directions using weighed 8ncrements. The second build, on the nozzle, I used the 1/2 tablespoon for the clay(it says this in the text). When I checked today, the 1/2 tablespoon was only about 1/2 as much clay as I had used the first time. So, I measured out the weighed amount again and used that. Perhaps the nozzle wasn't formed properly in my failed atemt?

I'll report back and thanks again for your replies.

[FlaMtnBkr]

Try lighting it at the top of the core. Some quickmatch or taped up fuse will do it. But if you are that close to the fly, no fly point you need to do something to get the power up.

 

I didn't read the link so I'm assuming it's a core burner. If not you really need to have hot BP to get a good working end burner rocket.

[Leatherlips]

Well I just tried the third incarnation and it's another failure. I didn't read FlaMtnBkr's post on the fusing prior to my attempt. I had taken some fast paper fuse and inserted it all the way up the core but I didn't wrap it in tape as mentioned.

 

So, is there a way to try and increase the "power" of the current batch of rocket fuel or do I need to start over from scratch?

[stix]

You "could" increase the power of the fuel, but the issue with that would be repeatability. ie. how would you make the next batch? But I'm sure you could use the fuel for something so it wouldn't be wasted. I don't think it's the fuel anyway.

 

The fact that you have had two failures, at least gives you an opportunity to inspect the motor casings (providing you still have them). Was there any major erosion of the nozzle throat? it should be measured and compared. Was there "blow through" somewhere on the casing? Have a really detailed look at it.

 

Ideally with core burners they should be ignited high up as possible into the core, but I doubt that's the issue. The flame will propagate up the core pretty quickly anyway.

 

The fact that you had success to begin with points to a failure of methodology, not the fuel.

 

Cheers.

[schroedinger]

To increase the power of your actual batch, just mill it for about 10-20 minutes.

[stix]

To increase the power of your actual batch, just mill it for about 10-20 minutes.

 

I'm not sure if Leatherlips actually mentioned having a ballmill. Nevertheless, a possible "quick fix" solution does not address the underlying problems that Lips is having.

 

I have a similar issue making flapjacks - I can never remember the recipe, it's always far too watery. My "LAZY" way out is to just put some more flour in. It then becomes very lumpy so I have to spend considerable time getting the lumps out. It all works out sort of fine in the end and I get away with it. I guess I should try to remember the proper recipe for next time, but I never can. Afterall it's not pyrotechnics, it's only flapjacks.

 

Cheers.

[Leatherlips]

Thanks all again for the replies. Using that skylighter article, My first (successful) try was step by step from the article. the second (failure) was not step by step and I just went from memory, didn't use the specific weights for each increment of fuel I was pressing, etc. however, after that failure I went back to the article and again went step by step.
The Clay I used was all from the same "batch" that I milled (ground) and it was saved in an airtight container (as was the batch of fuel created from the article). I used the same tooling for all three builds. The only variable I can think of between the first and third attempt was the amount of pressure(using the arbor press) I could have used to press each increment while building the engine. in this last try I was very sure to apply as much pressure as I could on each increment, but on the first build I may have applied LESS pressure (I can't be sure as I dont have a guage).

 

i don't see any blow-through and I'll take measurements on the nozzle and compare it to the next attempt.

 

If anyone sees anything from the pics or has other suggestions, please share!

 

[Leatherlips]

BTW, I do have a ball mill (i've not used it yet) and I'll give that a try at least to see if it makes a difference. I assume the ball milling will negate the use of the larger mesh charcoal in the recipe (below)? The article was to make a glitter tail rocket which i'm assuming the larger mesh charcoal is the "glitter" .

Basic Black Powder Rocket Fuel Ratio 24-ounce batch

Potassium nitrate 0.6 14.4 ounces

Airfloat charcoal 0.1 2.4 ounces

80-mesh charcoal 0.18 4.3 ounces

36-mesh charcoal 0.02 0.5 ounces

Sulfur 0.10 2.4 ounces

Edited February 23, 2015 by Leatherlips

[Oinikis]

So, you have essentially used 6/3/1 BP rocket fuel which is quite underpowered I have to say. Maybe you should try traditional 75/15/10 BP and see what happens. Also your first (successful) rocket, how did it perform? Was the success that successful?

[Bobosan]

Lips, it appears you are reusing old tubes? (rocket #4 pic) If so, try using unfired new tubes for these first attempts.

 

Also, in rocket #4 pic, it looks like the tube has compressed and possibly split internally. This could result in CATO's also. Even pressure on the arbor press handle with a new tube would help a great deal. I've seen 3/8 or 1/2 drive sockets welded the the arbor shaft and then using a torque wrench to apply the same pressure on the fuel.

[Leatherlips]

oinikis, on the first attempt I thought it was successful, but did think it would have been better to get more height. I'm not sure what payload a 1lb rocket normally carries, but this one had a 2" cylinder shell loaded, plus a 2" comet. Since these are my first attempts I can't say for sure if there were specifics of the flight that could have been better but it looked pretty good to an untrained eye like my own. That said, I wasn't aware that the fuel "recipe" was not standard so I'll make a batch of what you described to see if I get better results.

Bobosan, The tubes were new when I pressed them. I do see the wrinkle you're referring to and I'm sure that was me applying too much pressure on one or more increments of fuel. I'll look into modifying the press, and perhaps I'll see if I can find/make a "sleeve" for the engine while pressing that would help in the interim.

[FlaMtnBkr]

Try reading up on waxing tubes. Basically a thin layer of wax is applied that helps lubricate when pressing and also acts like a fire block if there are any cracks along the tube interface that can cause CATOs. You're essentially inhibiting the grain (length of pressed fuel) in place. It has drastically decreased the amount of CATOs for those that have tried it. And it will help stop those tube wrinkles and quiet the pressing process if you are getting a creaking noise.

 

But your problem is the other end of the spectrum with not enough power. Which makes me think it's your fuel and not your process. Try milling your fuel but leave the coarse charcoal out and add it (and any metals) last after milling is complete. This will get your fuel hotter and your rockets in the air. You can always press more rockets with your current batch of fuel and turn them upside down for a nice fountain!

 

You can also use a formula with more nitrate that will also get it hotter if you don't want to mill yet. 75-15-10 is considered the ideal BP ratio for the hottest powder. So getting closer to that will help speed things up. You just have less charcoal so will have less sparks for a nice tail. I would get them flying and worry about a pretty tail later. But if you get your fuel too hot they can start blowing up on you and they can be surprisingly loud when the bigger ones pop.

 

I know this is kind of vague but part of fireworks is finding what works for you. If you would like specific things to try just say so.

[Leatherlips]

Just adding this pic of the engine opened up.

[Leatherlips]

You can also use a formula with more nitrate that will also get it hotter if you don't want to mill yet. 75-15-10 is considered the ideal BP ratio for the hottest powder. So getting closer to that will help speed things up.

I'll make the change in the BP and see if I can at least get these off the ground. Thanks again!

[Leatherlips]

One quick question, could I use Goex FFFF black powder for fuel?

[dagabu]

One quick question, could I use Goex FFFF black powder for fuel?

 

Certainly, you can use Goex but since it consists of hard grains, you will have to press the motors with more force to compact the fuel.

 

Lets go back to the first rocket that flew. If you bought the charcoal, you got a range of charcoal sizes, 36 mesh is the average, it will have larger and smaller grains in it. When scooping the charcoal out of the tub, you would normally take the top where the largest grains are and that can choke the nozzle enough to increase the thrust to the point of a good flight.

 

Try it again and the nozzle stays open giving a poor performance.

 

Keep the comp you have to be pressed above the spindle, make another batch of BP using the 75:15:10 comp and use 70:30 rubbing alcohol to whet it then granulate it and then dry it thoroughly. Use that BP for your rocket and see if it CATO's, if not, you are good to go. If it does pop, back off from pressing the entire motor with the hot BP and use your glitter on top to tame the fast BP and give you a nice tail.

 

Let me know if you need a tube support, it takes me just a few minutes to make a PVC support.

Edited February 24, 2015 by dagabu

[stix]

The fact that you had success to begin with points to a failure of methodology, not the fuel.

 

I have to aplogise for the statement above - now looking at the image you posted, it seems like there is a lot of unburnt fuel.

I think dagabu is pointing you in a good direction.

 

Cheers.

Edited February 24, 2015 by stix

[Leatherlips]

Dagbu, 70/30 is 70 alcohol 30 water? (Denatured or rubbing, or doesn't matter?)

I did create a tube support from pvc last night. I'll give this a try.

Thanks again to all who have replied. I'm learning quite a bit from my failure!

[dagabu]

Rubbing, it's the cheapest stuff you can get at the dollar store (good news for us), It was developed by David Forstner Forster in his attempts to copy Ned Gorski's scratch mix.

 

When making a PVC tube support, put it in an oven set to 250° for 10 minutes, it becomes pliable and will fit perfectly if rolled on the tube of choice while it is cooling down.

Edited February 25, 2015 by dagabu

[Leatherlips]

Thanks! I like the oven idea, that'll make it much easier for me.

[dagabu]

Thanks! I like the oven idea, that'll make it much easier for me.

 

Yupper, you can use any drain pipe or sched 40-80 to make plates, supports etc. For future reference, just slit a PVC tube that is larger than your rocket tube and throw it in the oven for 10 minutes. Find two smooth sheets of plywood/tile/marble etc that are bigger than your support and open up the tube, flatten it out on the tile etc and place the other on on top, add weight to flatten it all the way down.

 

Once cool, take a piece of string and wrap it around your tube, use a sharp marker and mark where the string overlaps, move that string to the PVC sheet and transfer the marks to the sheet and cut the sheet on those marks. Reheat the sheet and it will return to the form it was before you heated it and it will be EXACTLY the same size as your tube!

[wildcherryxoxo]

Rubbing, it's the cheapest stuff you can get at the dollar store (good news for us), It was developed by David Forstner in his attempts to copy Ned Gorski's scratch mix.

 

When making a PVC tube support, put it in an oven set to 250° for 10 minutes, it becomes pliable and will fit perfectly if rolled on the tube of choice while it is cooling down.

 

Just a bit of nitpicking here-

 

David Forster*

 

it wasnt an effort to copy "scratch mix" - the term "scratch mix" implies that the powder is hand mixed, and contains a binder. The whole point of alcohol binding is to granulate it without a binder,

 

Regards,

The Hairsplitter